"一 MyBatis 简介 MyBatis 是一个优秀的持久层框架它对 JDBC 操作数据库的过程进行封装开发者只需要关注 SQL 本身而不需要花费精力去处理 JDBC 繁杂的过程代码 MyBatis 将要执行的各种 Statement 配置起来并通过 Java 对象和 Statement 中 ...."

someone1
AI专业者开发社区 1 号成员
AI开发者社区 • 0 回帖 • 2 浏览 • 4 个月前

MyBatis辟邪剑谱

一 MyBatis 简介

MyBatis 是一个优秀的持久层框架它对 JDBC 操作数据库的过程进行封装开发者只需要关注 SQL 本身而不需要花费精力去处理 JDBC 繁杂的过程代码

MyBatis 将要执行的各种 Statement 配置起来并通过 Java 对象和 Statement 中的 SQL 进行映射生成最终执行的 SQL 语句最后由 MyBatis 执行 SQL 并将结果映射成 Java 对象返回

二 MyBatis 优缺点

优点

1. 通过直接编写 SQL 语句可以直接对 SQL 进行性能优化

2. 学习门槛低学习成本低只要有 SQL 基础就可以学习 MyBatis 而且很容易上手

3. 由于直接编写 SQL 语句所以灵活多变代码维护性更好

缺点

1. 不支持数据库无关性即数据库发生变更要写多套代码进行支持移植性不好比如分页关键字

2. 需要编写结果映射

三 MyBatis 框架核心

1. MyBatis 配置文件包括 MyBatis 全局配置文件和 MyBatis 映射文件其中全局配置文件配置了数据源事务等信息映射文件配置了 SQL 执行相关的信息

2. MyBatis 通过读取配置文件构造出 SqlSessionFactory 即会话工厂

3. 通过 SqlSessionFactory 可以创建 SqlSession 即会话 MyBatis 是通过 SqlSession 来操作数据库

4. SqlSession 本身不能直接操作数据库它是通过底层的 Executor 执行器接口来操作数据库 Executor 接口有两个实现类一个是普通执行器一个是缓存执行器 (默认)

5. Executor 执行器要处理的 SQL 信息是封装到一个底层对象 MappedStatement 中该对象包括 SQL 语句输入参数映射信息输出结果映射信息其中输入参数和输出结果的映射类型包括 HashMap 集合对象 POJO 对象类型

四 MyBatis 初体验

1. 新建一个 Maven 项目

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.hy.mybatis</groupId>
    <artifactId>mybatis-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 定义依赖版本号 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">properties</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">junit.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>4.12<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">junit.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">slf4j-log4j12.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>1.7.25<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">slf4j-log4j12.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">mysql-connector-java.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>8.0.11<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">mysql-connector-java.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">mybatis.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>3.4.6<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">mybatis.version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">properties</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 管理jar版本号 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependencyManagement</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> junit </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>junit<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>junit<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>${junit.version}<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> slf4j </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>org.slf4j<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>slf4j-log4j12<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>${slf4j-log4j12.version}<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> mysql </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mysql<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mysql-connector-java<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>${mysql-connector-java.version}<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> mybatis </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>org.mybatis<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mybatis<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>${mybatis.version}<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependencyManagement</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> junit </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>junit<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>junit<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> slf4j </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>org.slf4j<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>slf4j-log4j12<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> mysql </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mysql<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mysql-connector-java<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> mybatis </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>org.mybatis<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>mybatis<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">build</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">plugins</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 编译 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>org.apache.maven.plugins<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>maven-compiler-plugin<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>3.7.0<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">source</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>1.8<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">source</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">target</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>1.8<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">target</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">encoding</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>UTF-8<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">encoding</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">plugins</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">build</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</project>

sql

-- 用户表
CREATE TABLE user (
    id INT PRIMARY KEY AUTO_INCREMENT COMMENT '用户 id',
    username VARCHAR(32) COMMENT '用户名',
    money DOUBLE COMMENT '用户余额'
);
INSERT INTO user VALUES (1, '曹操', 8000);
INSERT INTO user VALUES (2, '孙权', 8000);
INSERT INTO user VALUES (3, '刘备', 8000);
INSERT INTO user VALUES (4, '诸葛亮', 5000);
INSERT INTO user VALUES (5, '司马懿', 5000);
INSERT INTO user VALUES (6, '张飞', 0);
INSERT INTO user VALUES (7, '关羽', 0);
INSERT INTO user VALUES (8, '马超', 1000);
INSERT INTO user VALUES (9, '黄忠', 1000);
INSERT INTO user VALUES (10, '赵云', 3000);
-- 订单表
CREATE TABLE order_ (
id INT PRIMARY KEY AUTO_INCREMENT COMMENT '订单 id',
create_date DATETIME COMMENT '订单创建时间',
note VARCHAR(100) COMMENT '订单备注',
uid INT COMMENT '用户 id'
);
ALTER TABLE order_ ADD CONSTRAINT order_fk FOREIGN KEY (uid) REFERENCES user (id);
INSERT INTO order_ VALUES (3, '2015-02-04 13:22:35', '配送快一点!', 1);
INSERT INTO order_ VALUES (4, '2015-02-03 13:22:41', NULL, 1);
INSERT INTO order_ VALUES (5, '2015-02-12 16:13:23', NULL, 10);
-- 商品表
CREATE TABLE item (
id INT PRIMARY KEY AUTO_INCREMENT COMMENT '商品 id',
name VARCHAR(32) COMMENT '商品名',
price DOUBLE COMMENT '商品价格',
detail VARCHAR(100) COMMENT '订单描述'
);
INSERT INTO item VALUES (1, '台式机', 3000.0, '该电脑质量非常好');
INSERT INTO item VALUES (2, '笔记本', 6000.0, '垃圾货色');
INSERT INTO item VALUES (3, '背包', 200.0, '名牌背包');
-- 订单商品关系表
CREATE TABLE order_detail (
id INT PRIMARY KEY AUTO_INCREMENT COMMENT 'id',
count INT COMMENT '购买数量',
oid INT COMMENT '订单 id',
iid INT COMMENT '商品 id'
);
ALTER TABLE order_detail ADD CONSTRAINT order_detail_order_fk FOREIGN KEY (oid) REFERENCES order_ (id);
ALTER TABLE order_detail ADD CONSTRAINT order_detail_item_fk FOREIGN KEY (iid) REFERENCES item (id);
INSERT INTO order_detail VALUES (1, 1, 3, 1);
INSERT INTO order_detail VALUES (2, 2, 3, 2);
INSERT INTO order_detail VALUES (3, 3, 4, 3);
INSERT INTO order_detail VALUES (4, 4, 4, 2);
-- 一个用户可以创建多个订单 用户表和订单表是一对多的关系
-- 一个订单可以包含多个商品 一个商品可以拥有多个订单 订单表和商品表是多对多的关系

2. 配置日志输出 resources/log4j.properties

### 输出到控制台 ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
输出到文件
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=//Users/HUANGYI/Downloads/x-log.txt
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
日志级别: fatal > error > warn > info > debug > trace
输出到哪里: stdout|file
#log4j.rootLogger=info, stdout
输出所有日志
log4j.rootLogger=all, stdout
不输出日志
#log4j.rootLogger=off, stdout

3. 配置数据源 resources/database.properties

url=jdbc:mysql://localhost:3306/demo_hy?characterEncoding=utf8&useSSL=false
driverClassName=com.mysql.cj.jdbc.Driver
username=root
password=root

4. 创建实体类 com.hy.mybatis.model.User

public class User implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String username;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Double money;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getUsername() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> username;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setUsername(String username) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.username =<span style="color: rgba(0, 0, 0, 1)"> username;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Double getMoney() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> money;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setMoney(Double money) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.money =<span style="color: rgba(0, 0, 0, 1)"> money;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "User{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", money=" + money +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

5. 创建 mapper 接口 com.hy.mybatis.mapper.UserMapper

/**
 * mapper 动态代理开发 MyBatis 会自动为 mapper 接口生成动态代理实现类
 * 必须遵循四个原则
 * 1. mapper 接口的全限定名要和 mapper 映射文件的 namespace 相同
 * 2. mapper 接口的方法名要和 mapper 映射文件的 statement#id 相同
 * 3. mapper 接口的方法参数只能有一个 且类型要和 mapper 映射文件的 statement#parameterType 相同
 * 4. mapper 接口的返回值类型要和 mapper 映射文件的 statement#resultType 或 statement#resultMap#type 相同
 * Created by Hy on 2020/7/29.
 */
public interface UserMapper {
User selectUserById(Integer id);

List</span>&lt;User&gt;<span style="color: rgba(0, 0, 0, 1)"> selectUserListByUsername(String username);

List</span>&lt;User&gt;<span style="color: rgba(0, 0, 0, 1)"> selectUserListByMoney(Map map);

Integer selectUserCount();

Integer insertUser(User user);

Integer deleteUserById(Integer id);

Integer updateUserById(User user);

}

6. 创建 mapper 映射文件 com.hy.mybatis.mapper.UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--
#{} 表示一个占位符 可以实现 preparedStatement 向占位符中设置值
#{} 可以有效防止 sql 注入 可以接收简单类型值或 pojo 属性值 如果 parameterType 传输单个简单类型值 括号中可以是 value 或其它名称
${} 表示拼接sql串 可以将parameterType传入的内容拼接在sql中
${} 会引起sql注入(谨慎使用) 可以接收简单类型值或pojo属性值 如果parameterType传输单个简单类型值 括号中只能是value
</span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>

<mapper namespace="com.hy.mybatis.mapper.UserMapper">
<!-- id: statement#id 要求在命名空间内唯一 -->
<!-- parameterType: statement#parameterType 入参的 java 类型 可以填写别名或 java 类的全限定名 -->
<!-- resultType: statement#resultType 单条查询结果对应的 java 类型 可以填写别名或 java 类的全限定名 -->
<select id="selectUserById" parameterType="Integer" resultType="User">
SELECT *
FROM user
WHERE id = #{value}
</select>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserListByUsername"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="String"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM user
    WHERE username LIKE '%${value}%'
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserListByMoney"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="HashMap"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM user
    LIMIT #{index}, #{count}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserCount"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT COUNT(id)
    FROM user
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">insert </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="insertUser"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 插入数据成功后 返回MySQL自增主键 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> keyProperty: 指定存放生成主键的属性 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> resultType: 生成主键所对应的java类型 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> order: 指定该查询主键sql语句的执行顺序 相对于insert语句 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">selectKey </span><span style="color: rgba(255, 0, 0, 1)">keyProperty</span><span style="color: rgba(0, 0, 255, 1)">="id"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> order</span><span style="color: rgba(0, 0, 255, 1)">="AFTER"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
        SELECT LAST_INSERT_ID()
    </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">selectKey</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    INSERT INTO user (username, money)
    VALUES (#{username}, #{money})
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">insert</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">delete </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="deleteUserById"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    DELETE FROM user
    WHERE id = #{value}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">delete</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">update </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="updateUserById"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    UPDATE user
    SET username = #{username}, money = #{money}
    WHERE id = #{id}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">update</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

7. 创建全局配置文件 resources/mybatis.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 引入数据源配置文件 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">properties </span><span style="color: rgba(255, 0, 0, 1)">resource</span><span style="color: rgba(0, 0, 255, 1)">="database.properties"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>

<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 别名 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">typeAliases</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 包指定 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">package </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="com.hy.mybatis.model"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">typeAliases</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">environments </span><span style="color: rgba(255, 0, 0, 1)">default</span><span style="color: rgba(0, 0, 255, 1)">="development"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">environment </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="development"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 使用jdbc事务管理 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">transactionManager </span><span style="color: rgba(255, 0, 0, 1)">type</span><span style="color: rgba(0, 0, 255, 1)">="JDBC"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 数据库连接池 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">dataSource </span><span style="color: rgba(255, 0, 0, 1)">type</span><span style="color: rgba(0, 0, 255, 1)">="POOLED"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">property </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="url"</span><span style="color: rgba(255, 0, 0, 1)"> value</span><span style="color: rgba(0, 0, 255, 1)">="${url}"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">property </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="driver"</span><span style="color: rgba(255, 0, 0, 1)"> value</span><span style="color: rgba(0, 0, 255, 1)">="${driverClassName}"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">property </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="username"</span><span style="color: rgba(255, 0, 0, 1)"> value</span><span style="color: rgba(0, 0, 255, 1)">="${username}"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">property </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="password"</span><span style="color: rgba(255, 0, 0, 1)"> value</span><span style="color: rgba(0, 0, 255, 1)">="${password}"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">dataSource</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">environment</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">environments</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> mapper文件位置 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">mappers</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 包指定 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">package </span><span style="color: rgba(255, 0, 0, 1)">name</span><span style="color: rgba(0, 0, 255, 1)">="com.hy.mybatis.mapper"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">mappers</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</configuration>

8. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test01() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    User user </span>= mapper.selectUserById(1<span style="color: rgba(0, 0, 0, 1)">);
    System.out.println(user.toString());
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test02() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;User&gt; userList = mapper.selectUserListByUsername("马"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (User user : userList) {
        System.out.println(user.toString());
    }
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test03() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 0, 255, 1)">int</span> page = 1<span style="color: rgba(0, 0, 0, 1)">;
    </span><span style="color: rgba(0, 0, 255, 1)">int</span> count = 5<span style="color: rgba(0, 0, 0, 1)">;
    </span><span style="color: rgba(0, 0, 255, 1)">int</span> index = (page - 1) *<span style="color: rgba(0, 0, 0, 1)"> count;
    Map</span>&lt;String, Integer&gt; map = <span style="color: rgba(0, 0, 255, 1)">new</span> HashMap&lt;&gt;<span style="color: rgba(0, 0, 0, 1)">();
    map.put(</span>"index"<span style="color: rgba(0, 0, 0, 1)">, index);
    map.put(</span>"count"<span style="color: rgba(0, 0, 0, 1)">, count);

    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;User&gt; userList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectUserListByMoney(map);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (User user : userList) {
        System.out.println(user.toString());
    }
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test04() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    Integer count </span>=<span style="color: rgba(0, 0, 0, 1)"> mapper.selectUserCount();
    System.out.println(</span>"count = " +<span style="color: rgba(0, 0, 0, 1)"> count);
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test05() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    User user </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> User();
    user.setUsername(</span>"貂蝉"<span style="color: rgba(0, 0, 0, 1)">);
    user.setMoney(</span>10.0<span style="color: rgba(0, 0, 0, 1)">);
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 返回受影响的行数</span>
    Integer count =<span style="color: rgba(0, 0, 0, 1)"> mapper.insertUser(user);
    System.out.println(</span>"受影响的行数 = " +<span style="color: rgba(0, 0, 0, 1)"> count);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 增删改需要提交事务</span>

        mSession.commit();
System.out.println("id =" + user.getId());
}
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test06() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 返回受影响的行数</span>
    Integer count = mapper.deleteUserById(12<span style="color: rgba(0, 0, 0, 1)">);
    System.out.println(</span>"受影响的行数 = " +<span style="color: rgba(0, 0, 0, 1)"> count);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 增删改需要提交事务</span>

        mSession.commit();
}
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test07() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    User user </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> User();
    user.setId(</span>13<span style="color: rgba(0, 0, 0, 1)">);
    user.setUsername(</span>"黄盖"<span style="color: rgba(0, 0, 0, 1)">);
    user.setMoney(</span>99.9<span style="color: rgba(0, 0, 0, 1)">);
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 返回受影响的行数</span>
    Integer count =<span style="color: rgba(0, 0, 0, 1)"> mapper.updateUserById(user);
    System.out.println(</span>"受影响的行数 = " +<span style="color: rgba(0, 0, 0, 1)"> count);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 增删改需要提交事务</span>

        mSession.commit();
}
}

五动态 SQL

<trim></trim> <if></if> <set></set> <where></where> <foreach></foreach> 使用示例

1. 创建实体类 com.hy.mybatis.model.Item

public class Item implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String name;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Double price;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String detail;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getName() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> name;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setName(String name) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.name =<span style="color: rgba(0, 0, 0, 1)"> name;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Double getPrice() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> price;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setPrice(Double price) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.price =<span style="color: rgba(0, 0, 0, 1)"> price;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getDetail() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> detail;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setDetail(String detail) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.detail =<span style="color: rgba(0, 0, 0, 1)"> detail;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "Item{" +
            "id=" + id +
            ", name='" + name + '\'' +
            ", price=" + price +
            ", detail='" + detail + '\'' +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

2. 创建 mapper 接口 com.hy.mybatis.mapper.ItemMapper

public interface ItemMapper {
Integer insertItem(Item item);

Integer updateItem(Item item);

List</span>&lt;Item&gt;<span style="color: rgba(0, 0, 0, 1)"> selectItemListByNameAndPrice(Item item);

List</span>&lt;Item&gt; selectItemListByIdArray(<span style="color: rgba(0, 0, 255, 1)">int</span><span style="color: rgba(0, 0, 0, 1)">[] array);

List</span>&lt;Item&gt;<span style="color: rgba(0, 0, 0, 1)"> selectItemListByIdList(List list);

}

3. 创建 mapper 映射文件 com.hy.mybatis.mapper.ItemMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.ItemMapper">
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">insert </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="insertItem"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    INSERT INTO item
    </span><span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;trim&gt;&lt;/trim&gt; 里面条件都不成立 什么也不添加 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;trim&gt;&lt;/trim&gt; 里面有任意条件成立 添加前缀 后缀 去除指定的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> prefix: 前缀 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> suffix: 后缀 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> prefixOverrides: 第一个 需要去除的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> suffixOverrides: 最后一个 需要去除的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">trim </span><span style="color: rgba(255, 0, 0, 1)">prefix</span><span style="color: rgba(0, 0, 255, 1)">="("</span><span style="color: rgba(255, 0, 0, 1)"> suffix</span><span style="color: rgba(0, 0, 255, 1)">=")"</span><span style="color: rgba(255, 0, 0, 1)"> suffixOverrides</span><span style="color: rgba(0, 0, 255, 1)">=","</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;if&gt;&lt;/if&gt; 判断入参 如果条件成立 则把标签体内的sql拼接上 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != id"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            id,
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != name"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            name,
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != price"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            price,
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != detail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            detail,
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">trim</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">trim </span><span style="color: rgba(255, 0, 0, 1)">prefix</span><span style="color: rgba(0, 0, 255, 1)">="VALUES ("</span><span style="color: rgba(255, 0, 0, 1)"> suffix</span><span style="color: rgba(0, 0, 255, 1)">=")"</span><span style="color: rgba(255, 0, 0, 1)"> suffixOverrides</span><span style="color: rgba(0, 0, 255, 1)">=","</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != id"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            #{id},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != name"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            #{name},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != price"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            #{price},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != detail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            #{detail},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">trim</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">insert</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">update </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="updateItem"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    UPDATE item
    </span><span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;set&gt;&lt;/set&gt; 里面条件都不成立 什么也不添加 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;set&gt;&lt;/set&gt; 里面有任意条件成立 添加SET 并去掉最后一个逗号 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">set</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != name"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            name = #{name},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != price"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            price = #{price},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != detail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            detail = #{detail},
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">set</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    WHERE id = #{id}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">update</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectItemListByNameAndPrice"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM item
    </span><span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;where&gt;&lt;/where&gt; 里面条件都不成立 什么也不添加 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> &lt;where&gt;&lt;/where&gt; 里面有任意条件成立 添加WHERE 并去掉第一个AND或OR </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != name and '' != name"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            AND name LIKE '%${name}%'
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != price and '' != price"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
            AND price </span><span style="color: rgba(255, 0, 0, 1)">&amp;lt;</span><span style="color: rgba(0, 0, 0, 1)"> #{price}
        </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectItemListByIdArray"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM item
    </span><span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != array and array.length &gt; 0"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> collection: 数组参数名称 如果传入包装类取数组属性名 如果直接传入数组只能填写array </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> item: 每次遍历出来的对象 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> separator: 每次遍历出来的对象 之间需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> open: 开始遍历时 需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> close: 结束遍历时 需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">foreach </span><span style="color: rgba(255, 0, 0, 1)">collection</span><span style="color: rgba(0, 0, 255, 1)">="array"</span><span style="color: rgba(255, 0, 0, 1)"> item</span><span style="color: rgba(0, 0, 255, 1)">="value"</span><span style="color: rgba(255, 0, 0, 1)"> separator</span><span style="color: rgba(0, 0, 255, 1)">=","</span><span style="color: rgba(255, 0, 0, 1)"> open</span><span style="color: rgba(0, 0, 255, 1)">="AND id IN ("</span><span style="color: rgba(255, 0, 0, 1)"> close</span><span style="color: rgba(0, 0, 255, 1)">=")"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
                #{value}
            </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">foreach</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectItemListByIdList"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM item
    </span><span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">if </span><span style="color: rgba(255, 0, 0, 1)">test</span><span style="color: rgba(0, 0, 255, 1)">="null != list and list.size &gt; 0"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> collection: 集合参数名称 如果传入包装类取集合属性名 如果直接传入集合只能填写list </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> item: 每次遍历出来的对象 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> separator: 每次遍历出来的对象 之间需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> open: 开始遍历时 需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> close: 结束遍历时 需要拼接的串 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">foreach </span><span style="color: rgba(255, 0, 0, 1)">collection</span><span style="color: rgba(0, 0, 255, 1)">="list"</span><span style="color: rgba(255, 0, 0, 1)"> item</span><span style="color: rgba(0, 0, 255, 1)">="value"</span><span style="color: rgba(255, 0, 0, 1)"> separator</span><span style="color: rgba(0, 0, 255, 1)">=","</span><span style="color: rgba(255, 0, 0, 1)"> open</span><span style="color: rgba(0, 0, 255, 1)">="AND id IN ("</span><span style="color: rgba(255, 0, 0, 1)"> close</span><span style="color: rgba(0, 0, 255, 1)">=")"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
                #{value}
            </span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">foreach</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">if</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">where</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

4. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test09() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    Item item </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Item();
    item.setName(</span>"自行车"<span style="color: rgba(0, 0, 0, 1)">);
    item.setPrice(</span>800.0<span style="color: rgba(0, 0, 0, 1)">);
    ItemMapper mapper </span>= mSession.getMapper(ItemMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 返回受影响的行数</span>
    Integer count =<span style="color: rgba(0, 0, 0, 1)"> mapper.insertItem(item);
    System.out.println(</span>"受影响的行数 = " +<span style="color: rgba(0, 0, 0, 1)"> count);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 增删改需要提交事务</span>

        mSession.commit();
}
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test10() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    Item item </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Item();
    item.setId(</span>4<span style="color: rgba(0, 0, 0, 1)">);
    item.setName(</span>"H2"<span style="color: rgba(0, 0, 0, 1)">);
    item.setPrice(</span>400000.0<span style="color: rgba(0, 0, 0, 1)">);
    item.setDetail(</span>"川崎"<span style="color: rgba(0, 0, 0, 1)">);
    ItemMapper mapper </span>= mSession.getMapper(ItemMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 返回受影响的行数</span>
    Integer count =<span style="color: rgba(0, 0, 0, 1)"> mapper.updateItem(item);
    System.out.println(</span>"受影响的行数 = " +<span style="color: rgba(0, 0, 0, 1)"> count);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 增删改需要提交事务</span>

        mSession.commit();
}
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test11() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    Item item </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Item();
    item.setName(</span>"包"<span style="color: rgba(0, 0, 0, 1)">);
    item.setPrice(</span>300.0<span style="color: rgba(0, 0, 0, 1)">);
    ItemMapper mapper </span>= mSession.getMapper(ItemMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;Item&gt; itemList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectItemListByNameAndPrice(item);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (Item i : itemList) {
        System.out.println(i.toString());
    }
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test12() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 0, 255, 1)">int</span>[] array = <span style="color: rgba(0, 0, 255, 1)">new</span> <span style="color: rgba(0, 0, 255, 1)">int</span>[]{1, 2<span style="color: rgba(0, 0, 0, 1)">};
    ItemMapper mapper </span>= mSession.getMapper(ItemMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;Item&gt; itemList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectItemListByIdArray(array);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (Item i : itemList) {
        System.out.println(i.toString());
    }
}

@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test13() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    List</span>&lt;Integer&gt; list = <span style="color: rgba(0, 0, 255, 1)">new</span> ArrayList&lt;&gt;<span style="color: rgba(0, 0, 0, 1)">();
    list.add(</span>1<span style="color: rgba(0, 0, 0, 1)">);
    list.add(</span>3<span style="color: rgba(0, 0, 0, 1)">);
    ItemMapper mapper </span>= mSession.getMapper(ItemMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;Item&gt; itemList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectItemListByIdList(list);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (Item i : itemList) {
        System.out.println(i.toString());
    }
}

}

六 resultMap 功能

1. 如果查询出来的列名和实体类属性名不一致通过定义一个 resultMap 将列名和实体类属性名绑定

a. 创建实体类 com.hy.mybatis.model.Order

public class Order implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Date createDate;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String note;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Date getCreateDate() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setCreateDate(Date createDate) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.createDate =<span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getNote() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> note;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setNote(String note) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.note =<span style="color: rgba(0, 0, 0, 1)"> note;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "Order{" +
            "id=" + id +
            ", createDate=" + createDate +
            ", note='" + note + '\'' +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

b. 创建 mapper 接口 com.hy.mybatis.mapper.OrderMapper

public interface OrderMapper {
List</span>&lt;Order&gt;<span style="color: rgba(0, 0, 0, 1)"> selectOrderList();

}

c. 创建 mapper 映射文件 com.hy.mybatis.mapper.OrderMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.OrderMapper">
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">resultMap </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="orderResultMap"</span><span style="color: rgba(255, 0, 0, 1)"> type</span><span style="color: rgba(0, 0, 255, 1)">="Order"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="id"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="create_date"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="createDate"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="note"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="note"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">resultMap</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectOrderList"</span><span style="color: rgba(255, 0, 0, 1)"> resultMap</span><span style="color: rgba(0, 0, 255, 1)">="orderResultMap"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM order_
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

d. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test08() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    OrderMapper mapper </span>= mSession.getMapper(OrderMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;Order&gt; orderList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectOrderList();
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (Order order : orderList) {
        System.out.println(order.toString());
    }
}

}

2. 一对一查询根据订单 id 查找订单包括用户信息

a. 创建实体类 com.hy.mybatis.model.OrderAndUser

public class OrderAndUser implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Date createDate;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String note;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> User user;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Date getCreateDate() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setCreateDate(Date createDate) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.createDate =<span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getNote() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> note;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setNote(String note) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.note =<span style="color: rgba(0, 0, 0, 1)"> note;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> User getUser() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> user;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setUser(User user) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.user =<span style="color: rgba(0, 0, 0, 1)"> user;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "OrderAndUser{" +
            "id=" + id +
            ", createDate=" + createDate +
            ", note='" + note + '\'' +
            ", user=" + user +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

b. 创建 mapper 接口 com.hy.mybatis.mapper.OrderMapper

public interface OrderMapper {
OrderAndUser selectOrderAndUserById(Integer id);

}

c. 创建 mapper 映射文件 com.hy.mybatis.mapper.OrderMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.OrderMapper">
<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 一对一 AS可以解决字段名重复问题 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">resultMap </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="orderAndUserResultMap"</span><span style="color: rgba(255, 0, 0, 1)"> type</span><span style="color: rgba(0, 0, 255, 1)">="OrderAndUser"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="id"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="create_date"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="createDate"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="note"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="note"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 关联内部对象 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">association </span><span style="color: rgba(255, 0, 0, 1)">property</span><span style="color: rgba(0, 0, 255, 1)">="user"</span><span style="color: rgba(255, 0, 0, 1)"> javaType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="uid"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="uusername"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="username"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="umoney"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="money"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">association</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">resultMap</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectOrderAndUserById"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> resultMap</span><span style="color: rgba(0, 0, 255, 1)">="orderAndUserResultMap"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT o.*, u.id AS uid, u.username AS uusername, u.money AS umoney
    FROM order_ o, user u
    WHERE o.uid = u.id
    AND o.id = #{value}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

d. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test14() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    OrderMapper mapper </span>= mSession.getMapper(OrderMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    OrderAndUser orderAndUser </span>= mapper.selectOrderAndUserById(3<span style="color: rgba(0, 0, 0, 1)">);
    System.out.println(orderAndUser.toString());
}

}

3. 一对多查询根据订单 id 查找订单包括订单明细信息

a. 创建实体类 com.hy.mybatis.model.OrderDetail com.hy.mybatis.model.OrderAndOrderDetail

public class OrderDetail implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer count;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Item item;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getCount() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> count;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setCount(Integer count) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.count =<span style="color: rgba(0, 0, 0, 1)"> count;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Item getItem() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> item;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setItem(Item item) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.item =<span style="color: rgba(0, 0, 0, 1)"> item;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "OrderDetail{" +
            "id=" + id +
            ", count=" + count +
            ", item=" + item +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

public class OrderAndOrderDetail implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Date createDate;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String note;
</span><span style="color: rgba(0, 0, 255, 1)">private</span> List&lt;OrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> orderDetailList;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Date getCreateDate() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setCreateDate(Date createDate) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.createDate =<span style="color: rgba(0, 0, 0, 1)"> createDate;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getNote() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> note;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setNote(String note) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.note =<span style="color: rgba(0, 0, 0, 1)"> note;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> List&lt;OrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> getOrderDetailList() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> orderDetailList;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> setOrderDetailList(List&lt;OrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> orderDetailList) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.orderDetailList =<span style="color: rgba(0, 0, 0, 1)"> orderDetailList;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "OrderAndOrderDetail{" +
            "id=" + id +
            ", createDate=" + createDate +
            ", note='" + note + '\'' +
            ", orderDetailList=" + orderDetailList +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

b. 创建 mapper 接口 com.hy.mybatis.mapper.OrderMapper

public interface OrderMapper {
OrderAndOrderDetail selectOrderAndOrderDetailById(Integer id);

}

c. 创建 mapper 映射文件 com.hy.mybatis.mapper.OrderMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.OrderMapper">
<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 一对多 AS可以解决字段名重复问题 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">resultMap </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="orderAndOrderDetailResultMap"</span><span style="color: rgba(255, 0, 0, 1)"> type</span><span style="color: rgba(0, 0, 255, 1)">="OrderAndOrderDetail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="id"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="create_date"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="createDate"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="note"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="note"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 关联内部集合 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">collection </span><span style="color: rgba(255, 0, 0, 1)">property</span><span style="color: rgba(0, 0, 255, 1)">="orderDetailList"</span><span style="color: rgba(255, 0, 0, 1)"> ofType</span><span style="color: rgba(0, 0, 255, 1)">="OrderDetail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="odid"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="odcount"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="count"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">collection</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">resultMap</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectOrderAndOrderDetailById"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> resultMap</span><span style="color: rgba(0, 0, 255, 1)">="orderAndOrderDetailResultMap"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT o.*, od.id AS odid, od.count AS odcount
    FROM order_ o, order_detail od
    WHERE o.id = od.oid
    AND o.id = #{value}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

d. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test15() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    OrderMapper mapper </span>= mSession.getMapper(OrderMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    OrderAndOrderDetail orderAndOrderDetail </span>= mapper.selectOrderAndOrderDetailById(3<span style="color: rgba(0, 0, 0, 1)">);
    System.out.println(orderAndOrderDetail.toString());
}

}

4. 多对多查询查询所有用户信息及用户购买的商品信息

a. 创建实体类 com.hy.mybatis.model.UserAndOrderDetail

public class UserAndOrderDetail implements Serializable {
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Integer id;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> String username;
</span><span style="color: rgba(0, 0, 255, 1)">private</span><span style="color: rgba(0, 0, 0, 1)"> Double money;
</span><span style="color: rgba(0, 0, 255, 1)">private</span> List&lt;OrderAndOrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> orderAndOrderDetailList;

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Integer getId() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setId(Integer id) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.id =<span style="color: rgba(0, 0, 0, 1)"> id;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String getUsername() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> username;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setUsername(String username) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.username =<span style="color: rgba(0, 0, 0, 1)"> username;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Double getMoney() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> money;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> setMoney(Double money) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.money =<span style="color: rgba(0, 0, 0, 1)"> money;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> List&lt;OrderAndOrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> getOrderAndOrderDetailList() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> orderAndOrderDetailList;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> setOrderAndOrderDetailList(List&lt;OrderAndOrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> orderAndOrderDetailList) {
    </span><span style="color: rgba(0, 0, 255, 1)">this</span>.orderAndOrderDetailList =<span style="color: rgba(0, 0, 0, 1)"> orderAndOrderDetailList;
}

@Override
</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> String toString() {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> "UserAndOrderDetail{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", money=" + money +
            ", orderAndOrderDetailList=" + orderAndOrderDetailList +
            '}'<span style="color: rgba(0, 0, 0, 1)">;
}

}

b. 创建 mapper 接口 com.hy.mybatis.mapper.UserMapper

public interface UserMapper {
List</span>&lt;UserAndOrderDetail&gt;<span style="color: rgba(0, 0, 0, 1)"> selectUserAndOrderDetail();

}

c. 创建 mapper 映射文件 com.hy.mybatis.mapper.UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.UserMapper">
<!-- 多对多 AS 可以解决字段名重复问题 -->
<resultMap id="userAndOrderDetailResultMap" type="UserAndOrderDetail">
<id column="id" property="id" />
<result column="username" property="username" />
<result column="money" property="money" />
    <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 关联内部集合 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">collection </span><span style="color: rgba(255, 0, 0, 1)">property</span><span style="color: rgba(0, 0, 255, 1)">="orderAndOrderDetailList"</span><span style="color: rgba(255, 0, 0, 1)"> ofType</span><span style="color: rgba(0, 0, 255, 1)">="OrderAndOrderDetail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="o0"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="o1"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="createDate"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="o2"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="note"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>

        <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 关联内部集合 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">collection </span><span style="color: rgba(255, 0, 0, 1)">property</span><span style="color: rgba(0, 0, 255, 1)">="orderDetailList"</span><span style="color: rgba(255, 0, 0, 1)"> ofType</span><span style="color: rgba(0, 0, 255, 1)">="OrderDetail"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="od0"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="od1"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="count"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>

            <span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 关联内部对象 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">association </span><span style="color: rgba(255, 0, 0, 1)">property</span><span style="color: rgba(0, 0, 255, 1)">="item"</span><span style="color: rgba(255, 0, 0, 1)"> javaType</span><span style="color: rgba(0, 0, 255, 1)">="Item"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">id </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="i0"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="id"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="i1"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="name"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="i2"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="price"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
                <span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">result </span><span style="color: rgba(255, 0, 0, 1)">column</span><span style="color: rgba(0, 0, 255, 1)">="i3"</span><span style="color: rgba(255, 0, 0, 1)"> property</span><span style="color: rgba(0, 0, 255, 1)">="detail"</span> <span style="color: rgba(0, 0, 255, 1)">/&gt;</span>
            <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">association</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
        <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">collection</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
    <span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">collection</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">resultMap</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserAndOrderDetail"</span><span style="color: rgba(255, 0, 0, 1)"> resultMap</span><span style="color: rgba(0, 0, 255, 1)">="userAndOrderDetailResultMap"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT u.*, o.id o0, o.create_date o1, o.note o2, od.id od0, od.count od1, i.id i0, i.name i1, i.price i2, i.detail i3
    FROM user u, order_ o, order_detail od, item i
    WHERE u.id = o.uid
    AND o.id = od.oid
    AND od.iid = i.id;
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

d. 测试

public class XTest {
SqlSession mSession;

@Before
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> before() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 读取配置文件</span>
    InputStream inputStream = Resources.getResourceAsStream("mybatis.xml"<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建会话工厂</span>
    SqlSessionFactory factory = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> SqlSessionFactoryBuilder().build(inputStream);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建SqlSession</span>
    mSession =<span style="color: rgba(0, 0, 0, 1)"> factory.openSession();
}

@After
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> after() {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (<span style="color: rgba(0, 0, 255, 1)">null</span> != mSession) mSession.close(); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">关闭SqlSession</span>

    }
@Test
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span> test16() <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> IOException {
    UserMapper mapper </span>= mSession.getMapper(UserMapper.<span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)">);
    List</span>&lt;UserAndOrderDetail&gt; userAndOrderDetailList =<span style="color: rgba(0, 0, 0, 1)"> mapper.selectUserAndOrderDetail();
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)"> (UserAndOrderDetail detail : userAndOrderDetailList) {
        System.out.println(detail.toString());
    }
}

}

七 MyBatis 缓存

和大多数的持久化框架一样 MyBatis 也提供了缓存策略通过缓存策略来减少数据库的查询次数从而提高性能 MyBatis 中缓存分为一级缓存二级缓存

1. 一级缓存

默认开启

一级缓存是 SqlSession 级别的缓存当调用 SqlSession 的增删改等方法时就会清空一级缓存

第一次发起查询用户 id 为 1 的用户信息先去找缓存中是否有 id 为 1 的用户信息如果没有从数据库查询用户信息得到用户信息将用户信息存储到一级缓存中

如果 SqlSession 去执行增删改清空 SqlSession 中的一级缓存这样做可以让缓存中存储的是最新信息避免脏读

第二次发起查询用户 id 为 1 的用户信息先去找缓存中是否有 id 为 1 的用户信息缓存中有直接从缓存中获取用户信息

2. 二级缓存

需要手动开启

二级缓存是 Mapper 级别的缓存同一个 Mapper 下多个 SqlSession 可以共用二级缓存当调用其中某个 SqlSession 的增删改等方法时就会清空二级缓存

SqlSession1 去查询用户信息查询到用户信息会将查询数据存储到二级缓存中

如果 SqlSession3 去执行增删改将会清空该 Mapper 映射下的二级缓存区域的数据这样做可以让缓存中存储的是最新信息避免脏读

SqlSession2 去查询与 SqlSession1 相同的用户信息首先会去缓存中找是否存在数据如果存在直接从缓存中取出数据

二级缓存的开启与关闭

a. resources/mybatis.xml <properties/> 节点和 <typeAliases/> 节点之间配置

<settings>
    <!-- 开启二级缓存 -->
    <setting name="cacheEnabled" value="true" />
</settings>

b. 配置相关的 mapper 映射文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hy.mybatis.mapper.UserMapper">
<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> 开启二级缓存 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">cache</span><span style="color: rgba(0, 0, 255, 1)">&gt;&lt;/</span><span style="color: rgba(128, 0, 0, 1)">cache</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 128, 0, 1)">&lt;!--</span><span style="color: rgba(0, 128, 0, 1)"> useCache: true=使用二级缓存 false=禁用二级缓 </span><span style="color: rgba(0, 128, 0, 1)">--&gt;</span>
<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserById"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="Integer"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(255, 0, 0, 1)"> useCache</span><span style="color: rgba(0, 0, 255, 1)">="true"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM user
    WHERE id = #{value}
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

<span style="color: rgba(0, 0, 255, 1)">&lt;</span><span style="color: rgba(128, 0, 0, 1)">select </span><span style="color: rgba(255, 0, 0, 1)">id</span><span style="color: rgba(0, 0, 255, 1)">="selectUserListByUsername"</span><span style="color: rgba(255, 0, 0, 1)"> parameterType</span><span style="color: rgba(0, 0, 255, 1)">="String"</span><span style="color: rgba(255, 0, 0, 1)"> resultType</span><span style="color: rgba(0, 0, 255, 1)">="User"</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span><span style="color: rgba(0, 0, 0, 1)">
    SELECT *
    FROM user
    WHERE username LIKE '%${value}%'
</span><span style="color: rgba(0, 0, 255, 1)">&lt;/</span><span style="color: rgba(128, 0, 0, 1)">select</span><span style="color: rgba(0, 0, 255, 1)">&gt;</span>

</mapper>

二级缓存的注意事项

a. 使用二级缓存时所缓存的类一定要实现 java.io.Serializable 接口这种就可以使用序列化方式来保存对象

b. 默认的二级缓存不支持分布式

c. 二级缓存对细粒度的数据缓存实现不好比如对商品信息进行缓存由于商品信息访问量大但是要求用户每次查询都是最新的商品信息此时如果使用二级缓存就无法实现当一个商品发生变化只刷新该商品缓存信息而不刷新其他商品缓存信息因为二级缓存是 Mapper 级别当一个商品信息更新所有的商品信息缓存数据都会清空解决此类问题需要在业务层根据需要对数据有针对性的缓存

MyBatis辟邪剑谱

输出到文件

日志级别: fatal > error > warn > info > debug > trace

输出到哪里: stdout|file

输出所有日志

不输出日志

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MyBatis辟邪剑谱