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Mybatis教程-实战看这一篇就够了

本文目录

转自：https://blog.csdn.net/hellozpc/article/details/80878563

1. 从 JDBC 谈起

1.1. 使用 IDEA 创建 maven 工程

1.2. 引入 mysql 依赖包

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.32</version>
</dependency>

1.3. 准备数据

  • 创建数据库：
CREATE DATABASE ssmdemo;
  • 创建表：
DROP TABLE IF EXISTS tb_user;
CREATE TABLE tb_user (
id char(32) NOT NULL,
user_name varchar(32) DEFAULT NULL,
password varchar(32) DEFAULT NULL,
name varchar(32) DEFAULT NULL,
age int(10) DEFAULT NULL,
sex int(2) DEFAULT NULL,
birthday date DEFAULT NULL,
created datetime DEFAULT NULL,
updated datetime DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
  • 插入数据：
INSERT INTO ssmdemo.tb_user ( userName, password, name, age, sex, birthday, created, updated) VALUES ( ‘zpc’, ‘123456’, ‘鹏程’, ‘22’, ‘1’, ‘1990-09-02’, sysdate(), sysdate());
INSERT INTO ssmdemo.tb_user ( userName, password, name, age, sex, birthday, created, updated) VALUES ( ‘hj’, ‘123456’, ‘静静’, ‘22’, ‘1’, ‘1993-09-05’, sysdate(), sysdate());

1.4.JDBC 基础代码回顾

  • JDBCTest.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

/**


    

  • 

    @author Evan
    */
    public class JDBCTest {
    public static void main(String[] args) throws Exception {
    Connection connection = null;
    PreparedStatement prepareStatement = null;
    ResultSet rs = null;
    

     <span class="hljs-keyword">try</span> {
     <span class="hljs-comment">// 加载驱动</span>
     Class.forName(<span class="hljs-string">"com.mysql.jdbc.Driver"</span>);
     <span class="hljs-comment">// 获取连接</span>
     <span class="hljs-type">String</span> <span class="hljs-variable">url</span> <span class="hljs-operator">=</span> <span class="hljs-string">"jdbc:mysql://127.0.0.1:3306/ssmdemo"</span>;
     <span class="hljs-type">String</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-string">"root"</span>;
     <span class="hljs-type">String</span> <span class="hljs-variable">password</span> <span class="hljs-operator">=</span> <span class="hljs-string">"123456"</span>;
     connection = DriverManager.getConnection(url, user, password);
     <span class="hljs-comment">// 获取statement，preparedStatement</span>
     <span class="hljs-type">String</span> <span class="hljs-variable">sql</span> <span class="hljs-operator">=</span> <span class="hljs-string">"select * from tb_user where id=?"</span>;
     prepareStatement = connection.prepareStatement(sql);
     <span class="hljs-comment">// 设置参数</span>
     prepareStatement.setLong(<span class="hljs-number">1</span>, <span class="hljs-number">1l</span>);
     <span class="hljs-comment">// 执行查询</span>
     rs = prepareStatement.executeQuery();
     <span class="hljs-comment">// 处理结果集</span>
     <span class="hljs-keyword">while</span> (rs.next()) {
         System.out.println(rs.getString(<span class="hljs-string">"userName"</span>));
         System.out.println(rs.getString(<span class="hljs-string">"name"</span>));
         System.out.println(rs.getInt(<span class="hljs-string">"age"</span>));
         System.out.println(rs.getDate(<span class="hljs-string">"birthday"</span>));
     }
 } <span class="hljs-keyword">finally</span> {
     <span class="hljs-comment">// 关闭连接，释放资源</span>
     <span class="hljs-keyword">if</span> (rs != <span class="hljs-literal">null</span>) {
         rs.close();
     }
     <span class="hljs-keyword">if</span> (prepareStatement != <span class="hljs-literal">null</span>) {
         prepareStatement.close();
     }
     <span class="hljs-keyword">if</span> (connection != <span class="hljs-literal">null</span>) {
         connection.close();
     }
 }

    

    }
    }

1.5.JDBC 缺点分析

2.MyBatis 介绍

官方文档 http://www.mybatis.org/mybatis-3/getting-started.html

3.Mybaits 整体架构

4. 快速入门（quick start）

4.1. 引入依赖（pom.xml）

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.2.8</version>
</dependency>

4.2. 全局配置文件（mybatis-config.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">
<!-- 根标签 -->
<configuration>
<properties>
	<property name="driver" value="com.mysql.jdbc.Driver"/>
	<property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis-110?useUnicode=true&amp;characterEncoding=utf-8&amp;allowMultiQueries=true"/>
	<property name="username" value="root"/>
    	<property name="password" value="123456"/>
   </properties>

<!-- 环境，可以配置多个，default：指定采用哪个环境 -->
<environments default="test">
<!-- id：唯一标识 -->
<environment id="test">
<!-- 事务管理器，JDBC 类型的事务管理器 -->
<transactionManager type="JDBC" />
<!-- 数据源，池类型的数据源 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis-110" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
<environment id="development">
<!-- 事务管理器，JDBC 类型的事务管理器 -->
<transactionManager type="JDBC" />
<!-- 数据源，池类型的数据源 -->
<dataSource type="POOLED">
<property name="driver" value="${driver}" /> <!-- 配置了 properties，所以可以直接引用 -->
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>
</configuration>

4.3. 配置 Map.xml（MyMapper.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: 根标签，namespace：命名空间，随便写，一般保证命名空间唯一 -->
<mapper namespace="MyMapper">
   <!-- statement，内容：sql 语句。id：唯一标识，随便写，在同一个命名空间下保持唯一
      resultType：sql 语句查询结果集的封装类型,tb_user 即为数据库中的表
    -->
   <select id="selectUser" resultType="com.zpc.mybatis.User">
      select * from tb_user where id = #{id}
   </select>
</mapper>

4.4. 修改全局配置文件（mybatis-config.xml）

配上 MyMapper.xml

<configuration>
   <!-- 环境，可以配置多个，default：指定采用哪个环境 -->
   <environments default="test">
      <!-- id：唯一标识 -->
      <environment id="test">
         <!-- 事务管理器，JDBC 类型的事务管理器 -->
         <transactionManager type="JDBC" />
         <!-- 数据源，池类型的数据源 -->
         <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver" />
            <property name="url" value="jdbc:mysql://127.0.0.1:3306/ssmdemo" />
            <property name="username" value="root" />
            <property name="password" value="123456" />
         </dataSource>
      </environment>
   </environments>
   <mappers>
     <mapper resource="mappers/MyMapper.xml" />
   </mappers>
</configuration>

4.5. 构建 sqlSessionFactory（MybatisTest.java）

	// 指定全局配置文件
        String resource = "mybatis-config.xml";
        // 读取配置文件
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 构建 sqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

4.6. 打开 sqlSession 会话，并执行 sql（MybatisTest.java）

	 // 获取 sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 操作 CRUD，第一个参数：指定 statement，规则：命名空间 +“.”+statementId
        // 第二个参数：指定传入 sql 的参数：这里是用户 id
        User user = sqlSession.selectOne("MyMapper.selectUser", 1);
        System.out.println(user);

完整代码：

  • MybatisTest.java
mport com.zpc.test.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;


public class MybatisTest {
public static void main(String[] args) throws Exception {
// 指定全局配置文件
String resource = "mybatis-config.xml";
// 读取配置文件
InputStream inputStream = Resources.getResourceAsStream(resource);
// 构建 sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 获取 sqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
// 操作 CRUD，第一个参数：指定 statement，规则：命名空间 +“.”+statementId
// 第二个参数：指定传入 sql 的参数：这里是用户 id
User user = sqlSession.selectOne("MyMapper.selectUser", 1);
System.out.println(user);
} finally {
sqlSession.close();
}
}
}

  • User.java
import java.text.SimpleDateFormat;
import java.util.Date;

public class User {
private String id;
private String userName;
private String password;
private String name;
private Integer age;
private Integer sex;
private Date birthday;
private String created;
private String updated;


<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getId</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> id;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setId</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> id</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">id</span> = id;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getUserName</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> userName;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setUserName</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> userName</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">userName</span> = userName;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getPassword</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> password;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setPassword</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> password</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">password</span> = password;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getName</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> name;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setName</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> name</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">name</span> = name;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">Integer</span> <span class="hljs-title function_">getAge</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> age;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setAge</span>(<span class="hljs-params">Integer age</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">age</span> = age;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">Integer</span> <span class="hljs-title function_">getSex</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> sex;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setSex</span>(<span class="hljs-params">Integer sex</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">sex</span> = sex;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">Date</span> <span class="hljs-title function_">getBirthday</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> birthday;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setBirthday</span>(<span class="hljs-params"><span class="hljs-built_in">Date</span> birthday</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">birthday</span> = birthday;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getCreated</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> created;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setCreated</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> created</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">created</span> = created;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getUpdated</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> updated;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setUpdated</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> updated</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">updated</span> = updated;
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">toString</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> <span class="hljs-string">"User{"</span> +
            <span class="hljs-string">"id='"</span> + id + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", userName='"</span> + userName + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", password='"</span> + password + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", name='"</span> + name + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", age="</span> + age +
            <span class="hljs-string">", sex="</span> + sex +
            <span class="hljs-string">", birthday='"</span> + <span class="hljs-keyword">new</span> <span class="hljs-title class_">SimpleDateFormat</span>(<span class="hljs-string">"yyyy-MM-dd"</span>).<span class="hljs-title function_">format</span>(birthday) + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", created='"</span> + created + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">", updated='"</span> + updated + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">'}'</span>;
}



}

4.7. 目录结构

5. 分析

5.1. 引入日志依赖包（pom.xml）

会自动引入 log4j 以及 slf4j-api

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.5</version>
</dependency>

5.2. 添加 log4j.properties

log4j.rootLogger=DEBUG,A1
log4j.logger.org.apache=DEBUG
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH🇲🇲ss,SSS} [%t] [%c]-[%p] %m%n

再次运行程序会打印日志：

2018-06-30 19:53:37,554 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-06-30 19:53:37,818 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 2094411587.
2018-06-30 19:53:37,818 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,863 [main] [MyMapper.selectUser]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-06-30 19:53:37,931 [main] [MyMapper.selectUser]-[DEBUG] ==> Parameters: 1(Integer)
2018-06-30 19:53:37,953 [main] [MyMapper.selectUser]-[DEBUG] <==      Total: 1
User{id='1', userName='zpc', password='123456', name='鹏程', age=25, sex=1, birthday='1990-09-02', created='2018-06-30 18:20:18.0', updated='2018-06-30 18:20:18.0'}
2018-06-30 19:53:37,954 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,954 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,955 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Returned connection 2094411587 to pool.

5.3.MyBatis 使用步骤总结

  • 1)配置 mybatis-config.xml 全局的配置文件 (1、数据源，2、外部的 mapper)
  • 2) 创建 SqlSessionFactory
  • 3) 通过 SqlSessionFactory 创建 SqlSession 对象
  • 4) 通过 SqlSession 操作数据库 CRUD
  • 5)调用 session.commit() 提交事务
  • 6)调用 session.close() 关闭会话

6. 完整的 CRUD 操作

6.1. 创建 UserDao 接口

import com.zpc.mybatis.pojo.User;
import java.util.List;

public interface UserDao {


<span class="hljs-comment">/**
 * 根据id查询用户信息
 *
 * <span class="hljs-doctag">@param</span> id
 * <span class="hljs-doctag">@return</span>
 */</span>
<span class="hljs-keyword">public</span> User <span class="hljs-title function_">queryUserById</span><span class="hljs-params">(String id)</span>;

<span class="hljs-comment">/**
 * 查询所有用户信息
 *
 * <span class="hljs-doctag">@return</span>
 */</span>
<span class="hljs-keyword">public</span> List&lt;User&gt; <span class="hljs-title function_">queryUserAll</span><span class="hljs-params">()</span>;

<span class="hljs-comment">/**
 * 新增用户
 *
 * <span class="hljs-doctag">@param</span> user
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">insertUser</span><span class="hljs-params">(User user)</span>;

<span class="hljs-comment">/**
 * 更新用户信息
 *
 * <span class="hljs-doctag">@param</span> user
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">updateUser</span><span class="hljs-params">(User user)</span>;

<span class="hljs-comment">/**
 * 根据id删除用户信息
 *
 * <span class="hljs-doctag">@param</span> id
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">deleteUser</span><span class="hljs-params">(String id)</span>;



}

6.2. 创建 UserDaoImpl

import com.zpc.mybatis.dao.UserDao;
import com.zpc.mybatis.pojo.User;
import org.apache.ibatis.session.SqlSession;
import java.util.List;

public class UserDaoImpl implements UserDao {
public SqlSession sqlSession;


<span class="hljs-keyword">public</span> <span class="hljs-title class_">UserDaoImpl</span>(<span class="hljs-title class_">SqlSession</span> sqlSession) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span> = sqlSession;
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-title class_">User</span> <span class="hljs-title function_">queryUserById</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> id</span>) {
    <span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span>.<span class="hljs-title function_">selectOne</span>(<span class="hljs-string">"UserDao.queryUserById"</span>, id);
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-title class_">List</span>&lt;<span class="hljs-title class_">User</span>&gt; <span class="hljs-title function_">queryUserAll</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span>.<span class="hljs-title function_">selectList</span>(<span class="hljs-string">"UserDao.queryUserAll"</span>);
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">insertUser</span>(<span class="hljs-params">User user</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span>.<span class="hljs-title function_">insert</span>(<span class="hljs-string">"UserDao.insertUser"</span>, user);
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">updateUser</span>(<span class="hljs-params">User user</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span>.<span class="hljs-title function_">update</span>(<span class="hljs-string">"UserDao.updateUser"</span>, user);
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">deleteUser</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> id</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">sqlSession</span>.<span class="hljs-title function_">delete</span>(<span class="hljs-string">"UserDao.deleteUser"</span>, id);
}



}

6.3. 编写 UserDao 对应的 UserDaoMapper.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: 根标签，namespace：命名空间，随便写，一般保证命名空间唯一 -->
<mapper namespace="UserDao">
    <!-- statement，内容：sql 语句。id：唯一标识，随便写，在同一个命名空间下保持唯一
       resultType：sql 语句查询结果集的封装类型,tb_user 即为数据库中的表
     -->
    <!--<select id="queryUserById" resultType="com.zpc.mybatis.pojo.User">-->
    <!--select * from tb_user where id = #{id}-->
    <!--</select>-->

<span class="hljs-comment">&lt;!--使用别名--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"queryUserById"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
  select
   tuser.id as id,
   tuser.user_name as userName,
   tuser.password as password,
   tuser.name as name,
   tuser.age as age,
   tuser.birthday as birthday,
   tuser.sex as sex,
   tuser.created as created,
   tuser.updated as updated
   from
   tb_user tuser
   where tuser.id = #{id};



</select>


<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"queryUserAll"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    select * from tb_user;
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>

<span class="hljs-comment">&lt;!--插入数据--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">insert</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"insertUser"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    INSERT INTO tb_user (
    user_name,
    password,
    name,
    age,
    sex,
    birthday,
    created,
    updated
    )
    VALUES
    (
    #{userName},
    #{password},
    #{name},
    #{age},
    #{sex},
    #{birthday},
    now(),
    now()
    );
<span class="hljs-tag">&lt;/<span class="hljs-name">insert</span>&gt;</span>

<span class="hljs-tag">&lt;<span class="hljs-name">update</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"updateUser"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    UPDATE tb_user
    <span class="hljs-tag">&lt;<span class="hljs-name">trim</span> <span class="hljs-attr">prefix</span>=<span class="hljs-string">"set"</span> <span class="hljs-attr">suffixOverrides</span>=<span class="hljs-string">","</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"userName!=null"</span>&gt;</span>user_name = #{userName},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"password!=null"</span>&gt;</span>password = #{password},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"name!=null"</span>&gt;</span>name = #{name},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"age!=null"</span>&gt;</span>age = #{age},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"sex!=null"</span>&gt;</span>sex = #{sex},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"birthday!=null"</span>&gt;</span>birthday = #{birthday},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        updated = now(),
    <span class="hljs-tag">&lt;/<span class="hljs-name">trim</span>&gt;</span>
    WHERE
    (id = #{id});
<span class="hljs-tag">&lt;/<span class="hljs-name">update</span>&gt;</span>

<span class="hljs-tag">&lt;<span class="hljs-name">delete</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"deleteUser"</span>&gt;</span>
    delete from tb_user where id=#{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">delete</span>&gt;</span>



</mapper>

在 mybatis-config.xml 中添加配置：

<mappers>
    <mapper resource="mappers/MyMapper.xml"/>
    <mapper resource="mappers/UserDaoMapper.xml"/>
</mappers>

6.4. 添加 UserDao 的测试用例

Pom 文件中添加 junit 依赖

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

按住 Alt+Enter, 选择 create test

6.5. 编写 UserDao 的测试用例

import com.zpc.mybatis.dao.UserDao;
import com.zpc.mybatis.dao.impl.UserDaoImpl;
import com.zpc.mybatis.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

public class UserDaoTest {


<span class="hljs-keyword">public</span> UserDao userDao;
<span class="hljs-keyword">public</span> SqlSession sqlSession;

<span class="hljs-meta">@Before</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">setUp</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    <span class="hljs-comment">// mybatis-config.xml</span>
    <span class="hljs-type">String</span> <span class="hljs-variable">resource</span> <span class="hljs-operator">=</span> <span class="hljs-string">"mybatis-config.xml"</span>;
    <span class="hljs-comment">// 读取配置文件</span>
    <span class="hljs-type">InputStream</span> <span class="hljs-variable">is</span> <span class="hljs-operator">=</span> Resources.getResourceAsStream(resource);
    <span class="hljs-comment">// 构建SqlSessionFactory</span>
    <span class="hljs-type">SqlSessionFactory</span> <span class="hljs-variable">sqlSessionFactory</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">SqlSessionFactoryBuilder</span>().build(is);
    <span class="hljs-comment">// 获取sqlSession</span>
    sqlSession = sqlSessionFactory.openSession();
    <span class="hljs-built_in">this</span>.userDao = <span class="hljs-keyword">new</span> <span class="hljs-title class_">UserDaoImpl</span>(sqlSession);
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">queryUserById</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    System.out.println(<span class="hljs-built_in">this</span>.userDao.queryUserById(<span class="hljs-string">"1"</span>));
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">queryUserAll</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    List&lt;User&gt; userList = <span class="hljs-built_in">this</span>.userDao.queryUserAll();
    <span class="hljs-keyword">for</span> (User user : userList) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">insertUser</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setAge(<span class="hljs-number">16</span>);
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>(<span class="hljs-string">"1990/09/02"</span>));
    user.setName(<span class="hljs-string">"大鹏"</span>);
    user.setPassword(<span class="hljs-string">"123456"</span>);
    user.setSex(<span class="hljs-number">1</span>);
    user.setUserName(<span class="hljs-string">"evan"</span>);
    <span class="hljs-built_in">this</span>.userDao.insertUser(user);
    <span class="hljs-built_in">this</span>.sqlSession.commit();
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">updateUser</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());
    user.setName(<span class="hljs-string">"静鹏"</span>);
    user.setPassword(<span class="hljs-string">"654321"</span>);
    user.setSex(<span class="hljs-number">1</span>);
    user.setUserName(<span class="hljs-string">"evanjin"</span>);
    user.setId(<span class="hljs-string">"1"</span>);
    <span class="hljs-built_in">this</span>.userDao.updateUser(user);
    <span class="hljs-built_in">this</span>.sqlSession.commit();
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">deleteUser</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    <span class="hljs-built_in">this</span>.userDao.deleteUser(<span class="hljs-string">"4"</span>);
    <span class="hljs-built_in">this</span>.sqlSession.commit();
}



}

6.6. 目录结构

6.7. 解决数据库字段名和实体类属性名不一致的问题

查询数据的时候，发现查不到 userName 的信息，
User{id=‘2’, userName=‘null’, password=‘123456’, name=‘静静’, age=22, sex=0, birthday=‘1993-09-05’, created=‘2018-06-30 18:22:28.0’, updated=‘2018-06-30 18:22:28.0’}
原因：数据库的字段名是 user_name，POJO 中的属性名字是 userName
两端不一致，造成 mybatis 无法填充对应的字段信息。修改方法：在 sql 语句中使用别名。

  • 解决方案 1：在 sql 语句中使用别名：
<select id="queryUserById" resultType="com.zpc.mybatis.pojo.User">
   select
    tuser.id as id,
    tuser.user_name as userName,
    tuser.password as password,
    tuser.name as name,
    tuser.age as age,
    tuser.birthday as birthday,
    tuser.sex as sex,
    tuser.created as created,
    tuser.updated as updated
    from
    tb_user tuser
    where tuser.id = #{id};
</select>

  • 解决方案 2： 参考后面的 resultMap –mapper 具体的配置的时候

  • 解决方案 3：参考驼峰匹配 — mybatis-config.xml 的时候

7. 动态代理 Mapper 实现类

7.1. 思考上述 CRUD 中的问题

  • 1、接口 -> 实现类 ->mapper.xml
  • 2、实现类中，使用 mybatis 的方式非常类似
  • 3、xml 中的 sql statement 硬编码到 java 代码中。

思考：能否只写接口，不写实现类。只编写接口和 Mapper.xml 即可？

因为在 dao（mapper）的实现类中对 sqlsession 的使用方式很类似。因此 mybatis 提供了接口的动态代理。

7.2. 使用动态代理改造 CRUD

  • 修改测试用例的 setUp 方法
  • 执行 queryUserAll() 方法
org.apache.ibatis.binding.BindingException: Type interface com.zpc.mybatis.dao.UserDao is not known to the MapperRegistry.
	at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
	at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:655)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:222)
at com.zpc.mybatis.test.UserDaoTest.setUp(UserDaoTest.java:32)
  • 分析原因，在 UserMapper.xml 中配置接口的全路径
    mapper.xml namespace
    如果希望使用 mybatis 通过的动态代理的接口，就需要 namespace 中的值，和需要对应的 Mapper(dao) 接口的全路径一致。Mapper 中 Namespace 的定义本身是没有限制的，只要不重复即可，但如果使用 Mybatis 的 DAO 接口动态代理，则 namespace 必须为 DAO 接口的全路径，例如：com.zpc.mybatis.dao.UserDao
<mapper namespace="com.zpc.mybatis.dao.UserDao">

7.3. 完整的例子

1、创建 UserMapper 接口（对应原 UserDao）

public interface UserMapper {

/**
* 登录（直接使用注解指定传入参数名称）
* @param userName
* @param password
* @return
*/
public User login(@Param("userName") String userName, @Param("password") String password);


/**
* 根据表名查询用户信息（直接使用注解指定传入参数名称）
* @param tableName
* @return
*/
public List<User> queryUserByTableName(@Param("tableName") String tableName);


/**
* 根据 Id 查询用户信息
* @param id
* @return
*/
public User queryUserById(Long id);


/**
* 查询所有用户信息
* @return
*/
public List<User> queryUserAll();


/**
* 新增用户信息
* @param user
*/
public void insertUser(User user);


/**
* 根据 id 更新用户信息
* @param user
*/
public void updateUser(User user);


/**
* 根据 id 删除用户信息
* @param id
*/
public void deleteUserById(Long id);
}

2、创建 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: 根标签，namespace：命名空间，随便写，一般保证命名空间唯一 ，为了使用接口动态代理，这里必须是接口的全路径名 -->
<mapper namespace="com.zpc.mybatis.dao.UserMapper">
    <!--
       1.#{}, 预编译的方式 preparedstatement，使用占位符替换，防止 sql 注入，一个参数的时候，任意参数名可以接收
       2.${}, 普通的 Statement，字符串直接拼接，不可以防止 sql 注入，一个参数的时候，必须使用 ${value} 接收参数
     -->
    <select id="queryUserByTableName" resultType="com.zpc.mybatis.pojo.User">
        select * from ${tableName}
    </select>

<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"login"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    select * from tb_user where user_name = #{userName} and password = #{password}
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>

<span class="hljs-comment">&lt;!-- statement，内容：sql语句。
   id：唯一标识，随便写，在同一个命名空间下保持唯一，使用动态代理之后要求和方法名保持一致
   resultType：sql语句查询结果集的封装类型，使用动态代理之后和方法的返回类型一致；resultMap：二选一
   parameterType：参数的类型，使用动态代理之后和方法的参数类型一致
 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"queryUserById"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    select * from tb_user where id = #{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"queryUserAll"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    select * from tb_user
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>
<span class="hljs-comment">&lt;!-- 新增的Statement
   id：唯一标识，随便写，在同一个命名空间下保持唯一，使用动态代理之后要求和方法名保持一致
   parameterType：参数的类型，使用动态代理之后和方法的参数类型一致
   useGeneratedKeys:开启主键回写
   keyColumn：指定数据库的主键
   keyProperty：主键对应的pojo属性名
 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">insert</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"insertUser"</span> <span class="hljs-attr">useGeneratedKeys</span>=<span class="hljs-string">"true"</span> <span class="hljs-attr">keyColumn</span>=<span class="hljs-string">"id"</span> <span class="hljs-attr">keyProperty</span>=<span class="hljs-string">"id"</span>
        <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    INSERT INTO tb_user (
    id,
    user_name,
    password,
    name,
    age,
    sex,
    birthday,
    created,
    updated
    )
    VALUES
    (
    null,
    #{userName},
    #{password},
    #{name},
    #{age},
    #{sex},
    #{birthday},
    NOW(),
    NOW()
    );
<span class="hljs-tag">&lt;/<span class="hljs-name">insert</span>&gt;</span>
<span class="hljs-comment">&lt;!-- 
   更新的statement
   id：唯一标识，随便写，在同一个命名空间下保持唯一，使用动态代理之后要求和方法名保持一致
   parameterType：参数的类型，使用动态代理之后和方法的参数类型一致
 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">update</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"updateUser"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.zpc.mybatis.pojo.User"</span>&gt;</span>
    UPDATE tb_user
    <span class="hljs-tag">&lt;<span class="hljs-name">trim</span> <span class="hljs-attr">prefix</span>=<span class="hljs-string">"set"</span> <span class="hljs-attr">suffixOverrides</span>=<span class="hljs-string">","</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"userName!=null"</span>&gt;</span>user_name = #{userName},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"password!=null"</span>&gt;</span>password = #{password},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"name!=null"</span>&gt;</span>name = #{name},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"age!=null"</span>&gt;</span>age = #{age},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"sex!=null"</span>&gt;</span>sex = #{sex},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">if</span> <span class="hljs-attr">test</span>=<span class="hljs-string">"birthday!=null"</span>&gt;</span>birthday = #{birthday},<span class="hljs-tag">&lt;/<span class="hljs-name">if</span>&gt;</span>
        updated = now(),
    <span class="hljs-tag">&lt;/<span class="hljs-name">trim</span>&gt;</span>
    WHERE
    (id = #{id});
<span class="hljs-tag">&lt;/<span class="hljs-name">update</span>&gt;</span>
<span class="hljs-comment">&lt;!-- 
   删除的statement
   id：唯一标识，随便写，在同一个命名空间下保持唯一，使用动态代理之后要求和方法名保持一致
   parameterType：参数的类型，使用动态代理之后和方法的参数类型一致
 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">delete</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"deleteUserById"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"java.lang.String"</span>&gt;</span>
    delete from tb_user where id=#{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">delete</span>&gt;</span>



</mapper>

3、全局配置文件 mybatis-config.xml 引入 UserMapper.xml

<mappers>
    <mapper resource="mappers/MyMapper.xml"/>
    <mapper resource="mappers/UserDaoMapper.xml"/>
    <mapper resource="mappers/UserMapper.xml"/>
</mappers>

4、创建 UserMapper 测试用例

import com.zpc.mybatis.dao.UserMapper;
import com.zpc.mybatis.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import java.io.InputStream;
import java.util.Date;
import java.util.List;


public class UserMapperTest {


<span class="hljs-keyword">public</span> UserMapper userMapper;

<span class="hljs-meta">@Before</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">setUp</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    <span class="hljs-comment">// 指定配置文件</span>
    <span class="hljs-type">String</span> <span class="hljs-variable">resource</span> <span class="hljs-operator">=</span> <span class="hljs-string">"mybatis-config.xml"</span>;
    <span class="hljs-comment">// 读取配置文件</span>
    <span class="hljs-type">InputStream</span> <span class="hljs-variable">inputStream</span> <span class="hljs-operator">=</span> Resources.getResourceAsStream(resource);
    <span class="hljs-comment">// 构建sqlSessionFactory</span>
    <span class="hljs-type">SqlSessionFactory</span> <span class="hljs-variable">sqlSessionFactory</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">SqlSessionFactoryBuilder</span>().build(inputStream);
    <span class="hljs-comment">// 获取sqlSession</span>
    <span class="hljs-type">SqlSession</span> <span class="hljs-variable">sqlSession</span> <span class="hljs-operator">=</span> sqlSessionFactory.openSession(<span class="hljs-literal">true</span>);

    <span class="hljs-comment">// 1. 映射文件的命名空间（namespace）必须是mapper接口的全路径</span>
    <span class="hljs-comment">// 2. 映射文件的statement的id必须和mapper接口的方法名保持一致</span>
    <span class="hljs-comment">// 3. Statement的resultType必须和mapper接口方法的返回类型一致</span>
    <span class="hljs-comment">// 4. statement的parameterType必须和mapper接口方法的参数类型一致（不一定）</span>
    <span class="hljs-built_in">this</span>.userMapper = sqlSession.getMapper(UserMapper.class);
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserByTableName</span><span class="hljs-params">()</span> {
    List&lt;User&gt; userList = <span class="hljs-built_in">this</span>.userMapper.queryUserByTableName(<span class="hljs-string">"tb_user"</span>);
    <span class="hljs-keyword">for</span> (User user : userList) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testLogin</span><span class="hljs-params">()</span> {
    System.out.println(<span class="hljs-built_in">this</span>.userMapper.login(<span class="hljs-string">"hj"</span>, <span class="hljs-string">"123456"</span>));
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserById</span><span class="hljs-params">()</span> {
    System.out.println(<span class="hljs-built_in">this</span>.userMapper.queryUserById(<span class="hljs-string">"1"</span>));
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserAll</span><span class="hljs-params">()</span> {
    List&lt;User&gt; userList = <span class="hljs-built_in">this</span>.userMapper.queryUserAll();
    <span class="hljs-keyword">for</span> (User user : userList) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testInsertUser</span><span class="hljs-params">()</span> {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setAge(<span class="hljs-number">20</span>);
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());
    user.setName(<span class="hljs-string">"大神"</span>);
    user.setPassword(<span class="hljs-string">"123456"</span>);
    user.setSex(<span class="hljs-number">2</span>);
    user.setUserName(<span class="hljs-string">"bigGod222"</span>);
    <span class="hljs-built_in">this</span>.userMapper.insertUser(user);
    System.out.println(user.getId());
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testUpdateUser</span><span class="hljs-params">()</span> {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());
    user.setName(<span class="hljs-string">"静静"</span>);
    user.setPassword(<span class="hljs-string">"123456"</span>);
    user.setSex(<span class="hljs-number">0</span>);
    user.setUserName(<span class="hljs-string">"Jinjin"</span>);
    user.setId(<span class="hljs-string">"1"</span>);
    <span class="hljs-built_in">this</span>.userMapper.updateUser(user);
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testDeleteUserById</span><span class="hljs-params">()</span> {
    <span class="hljs-built_in">this</span>.userMapper.deleteUserById(<span class="hljs-string">"1"</span>);
}



}

目录结构：

7.4. 动态代理总结

8.mybatis-config.xml 详解

mybatis-config.xml 讲究严格的顺序，具体顺序遵循文档的顺序

8.1.properties 属性读取外部资源

properties 配置的属性都是可外部配置且可动态替换的，既可以在典型的 Java 属性文件中配置，亦可通过 properties 元素的子元素来传递。例如：

<properties resource="org/mybatis/example/config.properties">
  <property name="username" value="dev_user"/>
  <property name="password" value="F2Fa3!33TYyg"/>
</properties>

然后其中的属性就可以在整个配置文件中被用来替换需要动态配置的属性值。比如:

<dataSource type="POOLED">
  <property name="driver" value="${driver}"/>
  <property name="url" value="${url}"/>
  <property name="username" value="${username}"/>
  <property name="password" value="${password}"/>
</dataSource>

这个例子中的 username 和 password 将会由 properties 元素中设置的相应值来替换。 driver 和 url 属性将会由 config.properties 文件中对应的值来替换。这样就为配置提供了诸多灵活选择。

属性也可以被传递到 SqlSessionFactoryBuilder.build() 方法中。例如：

SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader, props);
// ... or ...
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader, environment, props);

如果属性在不只一个地方进行了配置，那么 MyBatis 将按照下面的顺序来加载：

  • 1）在 properties 元素体内指定的属性首先被读取。
  • 2）然后根据 properties 元素中的 resource 属性读取类路径下属性文件或根据 url 属性指定的路径读取属性文件，并覆盖已读取的同名属性。
  • 3）最后读取作为方法参数传递的属性，并覆盖已读取的同名属性。

因此，通过方法参数传递的属性具有最高优先级，resource/url 属性中指定的配置文件次之，最低优先级的是 properties 属性中指定的属性。

8.2.settings 设置

<settings>
    <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>

测试：
没有开启驼峰匹配：

2018-07-01 13:57:56,486 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 13:57:56,524 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 13:57:56,568 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='null', password='123456', name='大神', age=20, sex=2, birthday='2018-07-01', created='2018-07-01 13:36:09.0', updated='2018-07-01 13:36:09.0'}

开启驼峰匹配：

2018-07-01 13:58:40,599 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 13:58:40,642 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 13:58:40,661 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='大神', age=20, sex=2, birthday='2018-07-01', created='2018-07-01 13:36:09.0', updated='2018-07-01 13:36:09.0'}

8.3.typeAliases
类型别名是为 Java 类型命名的一个短的名字。它只和 XML 配置有关，存在的意义仅在于用来减少类完全限定名的冗余。

<typeAliases>
    <typeAlias type="com.zpc.mybatis.pojo.User" alias="User"/>
</typeAliases>

缺点：每个 pojo 类都要去配置。
解决方案：使用扫描包，扫描指定包下的所有类，扫描之后的别名就是类名（不区分大小写），建议使用的时候和类名一致。

<typeAliases>
    <!--type: 实体类的全路径。alias: 别名，通常首字母大写 -->
    <!--<typeAlias type="com.zpc.mybatis.pojo.User" alias="User"/>-->
    <package name="com.zpc.mybatis.pojo"/>
</typeAliases>

Mybatis 已经为普通的 Java 类型内建了许多相应的类型别名。它们都是大小写不敏感的.

8.4.typeHandlers（类型处理器）

无论是 MyBatis 在预处理语句（PreparedStatement）中设置一个参数时，还是从结果集中取出一个值时， 都会用类型处理器将获取的值以合适的方式转换成 Java 类型。可以重写类型处理器或创建你自己的类型处理器来处理不支持的或非标准的类型。

8.5.plugins（插件）拦截器

MyBatis 允许你在已映射语句执行过程中的某一点进行拦截调用。默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：

Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)

ParameterHandler (getParameterObject, setParameters)

ResultSetHandler (handleResultSets, handleOutputParameters)

StatementHandler (prepare, parameterize, batch, update, query)

现在一些 MyBatis 插件比如 PageHelper 都是基于这个原理，有时为了监控 sql 执行效率，也可以使用插件机制
原理：

自定义拦截器：

// ExamplePlugin.java
@Intercepts({@Signature(
  type= Executor.class,
  method = "update",
  args = {MappedStatement.class,Object.class})})
public class ExamplePlugin implements Interceptor {
  public Object intercept(Invocation invocation) throws Throwable {
    return invocation.proceed();
  }
  public Object plugin(Object target) {
    return Plugin.wrap(target, this);
  }
  public void setProperties(Properties properties) {
  }
}

配置：

<!-- mybatis-config.xml -->
<plugins>
  <plugin interceptor="org.mybatis.example.ExamplePlugin">
    <property name="someProperty" value="100"/>
  </plugin>
</plugins>

上面的插件将会拦截在 Executor 实例中所有的 “update” 方法调用， 这里的 Executor 是负责执行低层映射语句的内部对象。

8.6.environments(环境)

MyBatis 可以配置成适应多种环境，例如，开发、测试和生产环境需要有不同的配置；
尽管可以配置多个环境，每个 SqlSessionFactory 实例只能选择其一。
虽然，这种方式也可以做到很方便的分离多个环境，但是实际使用场景下，我们更多的是选择使用 spring 来管理数据源，来做到环境的分离。

8.7.mappers

需要告诉 MyBatis 到哪里去找到 SQL 映射语句。即告诉 MyBatis 到哪里去找映射文件。你可以使用相对于类路径的资源引用， 或完全限定资源定位符（包括 file:/// 的 URL），或类名和包名等。例如：

<!-- 使用相对于类路径的资源引用 -->
<mappers>
  <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
  <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
  <mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>

<!-- 使用映射器接口实现类的完全限定类名 -->
<mappers>
<mapper class="org.mybatis.builder.AuthorMapper"/>
<mapper class="org.mybatis.builder.BlogMapper"/>
<mapper class="org.mybatis.builder.PostMapper"/>
</mappers>

这里所谓的 mapper 接口路径。实际上就是 dao 的接口路径。在 mybatis 中，通常把 dao 的包叫做 mapper。类名，也叫做 mapper

  • 1、定义一个接口。
  • 2、在接口所在的包中定义 mapper.xml，并且要求 xml 文件和 interface 的名称要相同。
  • 3、在 mybatis-config.xml 中通过 class 路径，引入 mapper（注解方式）。要求 mapper.xml 中的名称空间是类的接口的全路径。

注解方式：

<mappers>
    <mapper resource="mappers/MyMapper.xml"/>
    <mapper resource="mappers/UserDaoMapper.xml"/>
    <!-- 注解方式可以使用如下配置方式 -->
    <mapper class="com.zpc.mybatis.dao.UserMapper"/>
</mappers>

问题：

  • 1、mapper.xml 和 java 文件没有分离。 之后的教程讲述和 spring 整合之后解决。
  • 2、需要一个一个的去加载 mapper。

当然也可以使用包扫描（必须使用注解方式，即在接口方法上使用注解，如 @Select("select * from tb_user")）：
缺点：

  • 1、如果包的路径有很多？
  • 2、mapper.xml 和 mapper.java 没有分离。
    spring 整合的时候解决。

9.Mapper XML 文件详解

9.1.CRUD 标签

9.1.1.select

select – 书写查询 sql 语句
select 中的几个属性说明：
id 属性：当前名称空间下的 statement 的唯一标识。必须。要求 id 和 mapper 接口中的方法的名字一致。
resultType：将结果集映射为 java 的对象类型。必须（和 resultMap 二选一）
parameterType：传入参数类型。可以省略

9.1.2.insert

insert 的几个属性说明：
id：唯一标识，随便写，在同一个命名空间下保持唯一，使用动态代理之后要求和方法名保持一致
parameterType：参数的类型，使用动态代理之后和方法的参数类型一致
useGeneratedKeys: 开启主键回写
keyColumn：指定数据库的主键
keyProperty：主键对应的 pojo 属性名
标签内部：具体的 sql 语句。

9.1.3.update

id 属性：当前名称空间下的 statement 的唯一标识 (必须属性)；
parameterType：传入的参数类型，可以省略。
标签内部：具体的 sql 语句。

9.1.4.delete

delete 的几个属性说明：
id 属性：当前名称空间下的 statement 的唯一标识 (必须属性)；
parameterType：传入的参数类型，可以省略。
标签内部：具体的 sql 语句。

9.2.#{} 和 ${}

场景：数据库有两个一模一样的表。历史表，当前表
查询表中的信息，有时候从历史表中去查询数据，有时候需要去新的表去查询数据。
希望使用 1 个方法来完成操作。

<select id="queryUserByTableName" resultType="com.zpc.mybatis.pojo.User">
    select * from #{tableName}
</select>

/**


    

  • 根据表名查询用户信息（直接使用注解指定传入参数名称）
    • 

  • 

  • @param tableName
    • 

  • @return
    */
    public List<User> queryUserByTableName(String tableName);

测试输出：

有问题, 报语法错误：相当于执行了这样一条 sql:
select * from “tb_user”;
显然表名多了引号。

改正：

<select id="queryUserByTableName" resultType="com.zpc.mybatis.pojo.User">
    select * from ${tableName}
</select>

注意：
#{} 只是替换？，相当于 PreparedStatement 使用占位符去替换参数，可以防止 sql 注入。
${} 是进行字符串拼接，相当于 sql 语句中的 Statement，使用字符串去拼接 sql；$ 可以是 sql 中的任一部分传入到 Statement 中，不能防止 sql 注入。

使用${} 去取出参数值信息，需要使用${value}
#{} 只是表示占位，与参数的名字无关，如果只有一个参数，会自动对应。

推荐：

/**
 * 根据表名查询用户信息（直接使用注解指定传入参数名称）
 *
 * @param tableName
 * @return
 */
public List<User> queryUserByTableName(@Param("tableName")String tableName);

<select id="queryUserByTableName" resultType="com.zpc.mybatis.pojo.User">
select * from ${tableName}
</select>

#{}多个参数时：

/**
 * 登录（直接使用注解指定传入参数名称）
 *
 * @param userName
 * @param password
 * @return
 */
public User login( String userName, String password);

<select id="login" resultType="com.zpc.mybatis.pojo.User">
select * from tb_user where user_name = #{userName} and password = #{password}
</select>

报错：

org.apache.ibatis.exceptions.PersistenceException: 
Error querying database.  Cause: org.apache.ibatis.binding.BindingException: Parameter 'userName' not found. Available parameters are [0, 1, param1, param2]
Cause: org.apache.ibatis.binding.BindingException: Parameter 'userName' not found. Available parameters are [0, 1, param1, param2]

解决方案一：

<select id="login" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user where user_name = #{0} and password = #{1}
</select>

解决方案二：

<select id="login" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user where user_name = #{param1} and password = #{param2}
</select>

最终解决方案：

/**
 * 登录（直接使用注解指定传入参数名称）
 *
 * @param userName
 * @param password
 * @return
 */
public User login(@Param("userName") String userName, @Param("password") String password);

<select id="login" resultType="com.zpc.mybatis.pojo.User">
select * from tb_user where user_name = #{userName} and password = #{password}
</select>

通常在方法的参数列表上加上一个注释 @Param(“xxxx”) 显式指定参数的名字，然后通过 ${“xxxx”} 或 #{“xxxx”}
sql 语句动态生成的时候，使用 ${};
sql 语句中某个参数进行占位的时候 #{}

9.3. 面试题（#、$ 区别）

/**
 * #号
 * @param username1
 * @return
 */
User queryUserListByName1(@Param("username1") String username1);

/**


    

  • $号
    • 

  • @param username2
    • 

  • @return
    */
    User queryUserListByName2(@Param("username2")String username2);
    • 



<select id="queryUserListByName1" resultType="com.zpc.mybatis.pojo.User">
select * from tb_user WHERE user_name=#{username1}
</select>


<select id="queryUserListByName2" resultType="com.zpc.mybatis.pojo.User">
select * from tb_user WHERE user_name='${username2}'//手动加了引号
</select>

9.4.resultMap

使用：

9.5.sql 片段

<sql id=””></sql>
<include refId=”” />

例如在 UserMapper.xml 中定义如下片段：

<sql id="commonSql">
		id,
			user_name,
			password,
			name,
			age,
			sex,
			birthday,
			created,
			updated	
</sql>

则可以在 UserMapper.xml 中使用它：

<select id="queryUserById" resultMap="userResultMap">
	select <include refid="commonSql"></include> from tb_user where id = #{id}
</select>

<select id="queryUsersLikeUserName" resultType="User">
select <include refid="commonSql"></include> from tb_user where user_name like "%"#{userName}"%"
</select>

Sql 片段也可以定义在单独的.xml 文件中如：
定义 CommonSQL.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="CommonSQL">
	<sql id="commonSql">
		id,
			user_name,
			password,
			name,
			age,
			sex,
			birthday,
			created,
			updated	
	</sql>
</mapper>

使用：

	<select id="queryUserById" resultMap="userResultMap">
		select <include refid="CommonSQL.commonSql"></include> from tb_user where id = #{id}
	</select>

&lt;<span class="hljs-keyword">select</span> id=<span class="hljs-string">"queryUsersLikeUserName"</span> resultType=<span class="hljs-string">"User"</span>&gt;
	<span class="hljs-keyword">select</span> &lt;include refid=<span class="hljs-string">"CommonSQL.commonSql"</span>&gt;&lt;/include&gt; <span class="hljs-keyword">from</span> tb_user <span class="hljs-keyword">where</span> user_name like <span class="hljs-string">"%"</span><span class="hljs-meta">#{userName}"%"</span>
&lt;/<span class="hljs-keyword">select</span>&gt;

当然要完成这个功能还需要在全局配置文件 mybatis-config.xml 中引入该外部配置文件：

<mappers>
		<mapper resource="CommonSQL.xml"/>
		<!-- 开启 mapper 接口的包扫描，基于 class 的配置方式 -->
		<package name="com.zpc.mybatis.mapper"/>
</mappers>

10. 动态 sql

场景：查询男性用户，如果输入了姓名，按姓名模糊查询

10.1.if

场景：查询男性用户，如果输入了姓名，则按姓名查询

定义接口：

/**
 * 查询男性用户，如果输入了姓名，则按姓名查询
 * @param name
 * @return
 */
List<User> queryUserList(@Param("name") String name);

编写 mapper

<select id="queryUserList" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user WHERE sex=1
    <if test="name!=null and name.trim()!=''">
      and name like '%${name}%'
    </if>
</select>

测试

@Test
public void testqueryUserList() {
    List<User> users = this.userMapper.queryUserList(null);
    for (User user : users) {
        System.out.println(user);
    }
}

10.2.choose when otherwise

场景：查询男性用户，如果输入了姓名则按照姓名模糊查找，否则如果输入了年龄则按照年龄查找，否则查找姓名为“鹏程”的用户。

定义接口：

/**
 * 查询男性用户，如果输入了姓名则按照姓名模糊查找，否则如果输入了年龄则按照年龄查找，否则查找姓名为“鹏程”的用户。
 * @param name
 * @param age
 * @return
 */
List<User> queryUserListByNameOrAge(@Param("name") String name,@Param("age") Integer age);

编写 mapper 配置：

<select id="queryUserListByNameOrAge" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user WHERE sex=1
    <!--
    1. 一旦有条件成立的 when，后续的 when 则不会执行
    2. 当所有的 when 都不执行时, 才会执行 otherwise
    -->
    <choose>
        <when test="name!=null and name.trim()!=''">
            and name like '%${name}%'
        </when>
        <when test="age!=null">
            and age = #{age}
        </when>
        <otherwise>
            and name='鹏程'
        </otherwise>
    </choose>
</select>

测试：

@Test
public void queryUserListByNameOrAge() throws Exception {
    List<User> users = this.userMapper.queryUserListByNameOrAge(null, 16);
    for (User user : users) {
        System.out.println(user);
    }
}

10.3.where 和 set

场景一：查询所有用户，如果输入了姓名按照姓名进行模糊查询，如果输入年龄，按照年龄进行查询，如果两者都输入，两个条件都要成立。

接口：

/**
 * 查询所有用户，如果输入了姓名按照姓名进行模糊查询，如果输入年龄，按照年龄进行查询，如果两者都输入，两个条件都要成立
 * @param name
 * @param age
 * @return
 */
List<User> queryUserListByNameAndAge(@Param("name") String name,@Param("age") Integer age);

配置：

<select id="queryUserListByNameAndAge" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user
    <!-- 如果多出一个 and，会自动去除，如果缺少 and 或者多出多个 and 则会报错 -->
    <where>
        <if test="name!=null and name.trim()!=''">
            and name like '%${name}%'
        </if>
        <if test="age!=null">
            and age = #{age}
        </if>
    </where>
</select>

测试：

@Test
public void queryUserListByNameAndAge() throws Exception {
    List<User> users = this.userMapper.queryUserListByNameAndAge("鹏程", 20);
    for (User user : users) {
        System.out.println(user);
    }
}

场景二：修改用户信息，如果参数 user 中的某个属性为 null，则不修改。
接口：

/**
 * 根据 id 更新用户信息
 *
 * @param user
 */
public void updateUser(User user);

配置：

<update id="updateUser" parameterType="com.zpc.mybatis.pojo.User">
    UPDATE tb_user
    <trim prefix="set" suffixOverrides=",">
        <if test="userName!=null">user_name = #{userName},</if>
        <if test="password!=null">password = #{password},</if>
        <if test="name!=null">name = #{name},</if>
        <if test="age!=null">age = #{age},</if>
        <if test="sex!=null">sex = #{sex},</if>
        <if test="birthday!=null">birthday = #{birthday},</if>
        updated = now(),
    </trim>
    WHERE
    (id = #{id});
</update>

测试：

@Test
public void testUpdateUser() {
    User user = new User();
    user.setBirthday(new Date());
    user.setName("静静");
    user.setPassword("123456");
    user.setSex(0);
    user.setUserName("Jinjin");
    user.setId("1");
    this.userMapper.updateUser(user);
}

10.4.foreach

场景：按照多个 id 查询用户信息

接口：

/**
 * 按多个 Id 查询
 * @param ids
 * @return
 */
List<User> queryUserListByIds(@Param("ids") String[] ids);

配置：

<select id="queryUserListByIds" resultType="com.zpc.mybatis.pojo.User">
    select * from tb_user where id in
    <foreach collection="ids" item="id" open="(" close=")" separator=",">
        #{id}
    </foreach>
</select>

测试：

@Test
public void queryUserListByIds() throws Exception {
    List<User> users = this.userMapper.queryUserListByIds(new String[]{"1","2"});
    for (User user : users) {
        System.out.println(user);
    }
}

If：testognl 表达式或者简单 java 代码
Choose when otherwise—> 相当于 if else if else
When test 参考 if
Where set 都有一定的纠错功能
Trim：prefix suffix prefixOverrides suffixOverrides
Foreach：collection item saparator open close

11. 缓存

11.1. 一级缓存

在 mybatis 中，一级缓存默认是开启的，并且一直无法关闭

一级缓存满足条件：

  • 1、同一个 session 中
  • 2、相同的 SQL 和参数

测试：

@Test
public void testQueryUserById() {
    System.out.println(this.userMapper.queryUserById("1"));
    System.out.println(this.userMapper.queryUserById("1"));
}

2018-07-01 17:08:50,156 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-07-01 17:08:50,421 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 242355057.
2018-07-01 17:08:50,423 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:08:50,476 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:08:50,509 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='鹏程', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 13:35:40.0'}
User{id='1', userName='bigGod222', password='123456', name='鹏程', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 13:35:40.0'}

使用：sqlSession.clearCache(); 可以强制清除缓存

测试：

@Test
public void testQueryUserById() {
    System.out.println(this.userMapper.queryUserById("1"));
    sqlSession.clearCache();
    System.out.println(this.userMapper.queryUserById("1"));
}

日志：

2018-07-01 17:10:51,065 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-07-01 17:10:51,359 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 242355057.
2018-07-01 17:10:51,360 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:10:51,408 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:10:51,437 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='鹏程', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 13:35:40.0'}
2018-07-01 17:10:51,438 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:10:51,438 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:10:51,440 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='鹏程', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 13:35:40.0'}

执行 update、insert、delete 的时候，会清空缓存
测试：

@Test
public void testQueryUserById() {
    System.out.println(this.userMapper.queryUserById("1"));
    //sqlSession.clearCache();

User user=<span class="hljs-keyword">new</span> User();
user.setName(<span class="hljs-string">"美女"</span>);
user.setId(<span class="hljs-string">"1"</span>);
userMapper.updateUser(user);

System.<span class="hljs-keyword">out</span>.println(<span class="hljs-keyword">this</span>.userMapper.queryUserById(<span class="hljs-string">"1"</span>));



}

日志：

2018-07-01 17:18:15,128 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-07-01 17:18:15,399 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 242355057.
2018-07-01 17:18:15,401 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:18:15,466 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:18:15,492 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='鹏程', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 13:35:40.0'}
2018-07-01 17:18:15,527 [main] [com.zpc.mybatis.dao.UserMapper.updateUser]-[DEBUG] ==>  Preparing: UPDATE tb_user set name = ?, updated = now() WHERE (id = ?); 
2018-07-01 17:18:15,529 [main] [com.zpc.mybatis.dao.UserMapper.updateUser]-[DEBUG] ==> Parameters: 美女(String), 1(String)
2018-07-01 17:18:15,532 [main] [com.zpc.mybatis.dao.UserMapper.updateUser]-[DEBUG] <==    Updates: 1
2018-07-01 17:18:15,532 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:18:15,533 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:18:15,538 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='美女', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 17:18:15.0'}

11.2. 二级缓存

mybatis 的二级缓存的作用域是一个 mapper 的 namespace ，同一个 namespace 中查询 sql 可以从缓存中命中。

开启二级缓存：

<mapper namespace="com.zpc.mybatis.dao.UserMapper">
    <cache/>
</mapper>

测试：

@Test
public void testCache() {
    System.out.println(this.userMapper.queryUserById("1"));

sqlSession.close();
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.<span class="hljs-keyword">class</span>);

System.<span class="hljs-keyword">out</span>.println(mapper.queryUserById(<span class="hljs-string">"1"</span>));



}

开启二级缓存，必须序列化：

public class User implements Serializable{
    private static final long serialVersionUID = -3330851033429007657L;

日志：

2018-07-01 17:23:39,335 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-07-01 17:23:39,664 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 2092769598.
2018-07-01 17:23:39,665 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==>  Preparing: select * from tb_user where id = ? 
2018-07-01 17:23:39,712 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] ==> Parameters: 1(String)
2018-07-01 17:23:39,734 [main] [com.zpc.mybatis.dao.UserMapper.queryUserById]-[DEBUG] <==      Total: 1
User{id='1', userName='bigGod222', password='123456', name='美女', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 17:18:15.0'}
2018-07-01 17:23:39,743 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cbd213e]
2018-07-01 17:23:39,744 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Returned connection 2092769598 to pool.
2018-07-01 17:23:39,746 [main] [com.zpc.mybatis.dao.UserMapper]-[DEBUG] Cache Hit Ratio [com.zpc.mybatis.dao.UserMapper]: 0.5
User{id='1', userName='bigGod222', password='123456', name='美女', age=20, sex=1, birthday='2018-07-01', created='2018-07-01 13:35:40.0', updated='2018-07-01 17:18:15.0'}

关闭二级缓存：
不开启，或者在全局的 mybatis-config.xml 中去关闭二级缓存

<settings>
    <!-- 开启驼峰匹配 -->
    <setting name="mapUnderscoreToCamelCase" value="true"/>
    <!-- 开启二级缓存, 全局总开关，这里关闭，mapper 中开启了也没用 -->
    <setting name="cacheEnabled" value="false"/>
</settings>

12. 高级查询

12.1. 表关系说明

创建 order 表：

CREATE TABLE tb_order (
id int(11) NOT NULL AUTO_INCREMENT,
user_id int(11) DEFAULT NULL,
order_number varchar(255) DEFAULT NULL,
create datetime DEFAULT NULL,
updated datetime DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

public class Order {
    private Integer id;
    private Long userId;
    private String orderNumber;
    private Date created;
    private Date updated;
}

需求说明：

12.2. 一对一查询

  • 方法一：核心思想扩展 Order 对象，来完成映射
    新建 OrderUser 实体类继承 Order：
public class OrderUser extends Order {
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private Integer sex;
    private Date birthday;
    private Date created;
    private Date updated;
}

OrderMapper 接口：

public interface OrderMapper {
     OrderUser queryOrderUserByOrderNumber(@Param("number") String number);
}

配置 OrderMapper：

 <mapper namespace="com.zpc.mybatis.dao.OrderMapper">
    <select id="queryOrderUserByOrderNumber" resultType="com.zpc.mybatis.pojo.OrderUser">
      select * from tb_order o left join tb_user u on o.user_id=u.id where o.order_number = #{number}
   </select>
</mapper>

测试：

@Test
public void queryOrderUserByOrderNumber() throws Exception {
    OrderUser orderUser = orderMapper.queryOrderUserByOrderNumber("201807010001");
    System.out.println(orderUser);
}
  • 方法二：面向对象的思想，在 Order 对象中添加 User 对象。

在 Order 对象中添加 User 属性：

public class Order {
    private Integer id;
    private Long userId;
    private String orderNumber;
    private Date created;
    private Date updated;
    private User user;
}

接口：

/**
 * 根据订单号查询订单用户的信息
 * @param number
 * @return
 */
Order queryOrderWithUserByOrderNumber(@Param("number") String number);

使用 resultType 不能完成自动映射，需要手动完成结果集映射 resultMap：

 <resultMap id="OrderUserResultMap" type="com.zpc.mybatis.pojo.Order" autoMapping="true">
     <id column="id" property="id"/>
     <!--association: 完成子对象的映射 -->
     <!--property: 子对象在父对象中的属性名 -->
     <!--javaType: 子对象的 java 类型 -->
     <!--autoMapping: 完成子对象的自动映射，若开启驼峰，则按驼峰匹配 -->
     <association property="user" javaType="com.zpc.mybatis.pojo.User" autoMapping="true">
         <id column="user_id" property="id"/>
     </association>
 </resultMap>

<select id="queryOrderWithUserByOrderNumber" resultMap="OrderUserResultMap">
select * from tb_order o left join tb_user u on o.user_id=u.id where o.order_number = #{number}
</select>

测试：

@Test
public void queryOrderWithUserByOrderNumber() throws Exception {
    Order order = orderMapper.queryOrderWithUserByOrderNumber("201807010001");
    System.out.println(order.getUser());
}

12.3. 一对多查询

一对多查询：查询订单，查询出下单人信息并且查询出订单详情。

Order 类：

public class Order {
    private Integer id;
    private Long userId;
    private String orderNumber;
    private Date created;
    private Date updated;
    private User user;
    private List<OrderDetail> detailList;
}

public class OrderDetail {
    private Integer id;
    private Integer orderId;
    private Double totalPrice;
    private Integer status;
}

接口：

/**
 * 根据订单号查询订单用户的信息及订单详情
 * @param number
 * @return
 */
Order queryOrderWithUserAndDetailByOrderNumber(@Param("number") String number);

Mapper 映射：

<resultMap id="OrderUserDetailResultMap" type="com.zpc.mybatis.pojo.Order" autoMapping="true">
    <id column="id" property="id"/>
    <!--collection: 定义子对象集合映射 -->
    <!--association: 完成子对象的映射 -->
    <!--property: 子对象在父对象中的属性名 -->
    <!--javaType: 子对象的 java 类型 -->
    <!--autoMapping: 完成子对象的自动映射，若开启驼峰，则按驼峰匹配 -->
    <association property="user" javaType="com.zpc.mybatis.pojo.User" autoMapping="true">
        <id column="user_id" property="id"/>
    </association>
    <collection property="detailList" javaType="List" ofType="com.zpc.mybatis.pojo.OrderDetail" autoMapping="true">
        <id column="id" property="id"/>
    </collection>
</resultMap>

<select id="queryOrderWithUserAndDetailByOrderNumber" resultMap="OrderUserDetailResultMap">
select * from tb_order o
left join tb_user u on o.user_id=u.id
left join tb_orderdetail od on o.id=od.order_id
where o.order_number = #{number}
</select>

测试：

@Test
public void queryOrderWithUserAndDetailByOrderNumber() throws Exception {
    Order order = orderMapper.queryOrderWithUserAndDetailByOrderNumber("201807010001");
    System.out.println(order.getUser());
    System.out.println(order.getDetailList());
}

12.4. 多对多查询

多对多查询：查询订单，查询出下单人信息并且查询出订单详情中的商品数据。

OrderDetail 类

public class OrderDetail {
    private Integer id;
    private Integer orderId;
    private Double totalPrice;
    private Integer status;
    private Item item;
}

public class Item {
private Integer id;
private String itemName;
private Float itemPrice;
private String itemDetail;
}

接口：

/**
 * 根据订单号查询订单用户的信息及订单详情及订单详情对应的商品信息
 * @param number
 * @return
 */
Order queryOrderWithUserAndDetailItemByOrderNumber(@Param("number") String number);

Mapper 配置：

<resultMap id="OrderUserDetailItemResultMap" type="com.zpc.mybatis.pojo.Order" autoMapping="true">
    <id column="id" property="id"/>
    <association property="user" javaType="com.zpc.mybatis.pojo.User" autoMapping="true">
        <id column="user_id" property="id"/>
    </association>
    <collection property="detailList" javaType="List" ofType="com.zpc.mybatis.pojo.OrderDetail" autoMapping="true">
        <id column="detail_id" property="id"/>
        <association property="item" javaType="com.zpc.mybatis.pojo.Item" autoMapping="true">
            <id column="item_id" property="id"/>
        </association>
    </collection>
</resultMap>

<select id="queryOrderWithUserAndDetailItemByOrderNumber" resultMap="OrderUserDetailItemResultMap">
select * ,od.id as detail_id from tb_order o
left join tb_user u on o.user_id=u.id
left join tb_orderdetail od on o.id=od.order_id
left join tb_item i on od.item_id=i.id
where o.order_number = #{number}
</select>

测试：

@Test
public void queryOrderWithUserAndDetailItemByOrderNumber() throws Exception {
    Order order = orderMapper.queryOrderWithUserAndDetailItemByOrderNumber("201807010001");
    System.out.println(order);
    System.out.println(order.getUser());
    System.out.println(order.getDetailList());
}

至此，目录结构如下：

数据库脚本：

CREATE TABLE tb_order (
id int(11) NOT NULL AUTO_INCREMENT,
user_id int(11) DEFAULT NULL,
order_number varchar(255) DEFAULT NULL,
create datetime DEFAULT NULL,
updated datetime DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
INSERT INTO tb_order VALUES (‘1’, ‘2’, ‘201807010001’, ‘2018-07-01 19:38:35’, ‘2018-07-01 19:38:40’);

CREATE TABLE tb_item (
id int(11) NOT NULL,
itemName varchar(255) DEFAULT NULL,
itemPrice decimal(10,2) DEFAULT NULL,
itemDetail varchar(255) DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO tb_item VALUES (‘1’, ‘袜子’, ‘29.90’, ‘香香的袜子’);
INSERT INTO tb_item VALUES (‘2’, ‘套子’, ‘99.99’, ‘冈本001’);


CREATE TABLE tb_orderdetail (
id int(11) NOT NULL AUTO_INCREMENT,
order_id int(11) DEFAULT NULL,
total_price decimal(10,0) DEFAULT NULL,
item_id int(11) DEFAULT NULL,
status int(10) unsigned zerofill DEFAULT NULL COMMENT ‘0成功非0失败’,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
INSERT INTO tb_orderdetail VALUES (‘1’, ‘1’, ‘10000’, ‘1’, ‘0000000001’);
INSERT INTO tb_orderdetail VALUES (‘2’, ‘1’, ‘2000’, ‘2’, ‘0000000000’);

12.5.resultMap 的继承

12.6. 高级查询的整理

resutlType 无法帮助我们自动的去完成映射，所以只有使用 resultMap 手动的进行映射
type 结果集对应的数据类型 id 唯一标识，被引用的时候，进行指定

<resultMap type="Order" id="orderUserLazyResultMap">
<!—定义pojo中的单个对象的 property 定义对象的属性名， javaType 属性的类型，
		<association property="user" javaType="User" autoMapping="true">
			<id />
		</association>
<!—如果属性是集合使用collection ,javaType 集合的类型，ofType 表示集中的存储的元素类型
		<collection property="details" javaType="List" ofType="OrderDetail" autoMapping="true">
			<id />
</resultMap>

13. 延迟加载

编写接口：

Mapper 配置：

测试：

结果：

开启延迟加载：

修改测试用例：

执行，报错：

添加 cglib：

<dependency>
		<groupId>cglib</groupId>
		<artifactId>cglib</artifactId>
		<version>3.1</version>
</dependency>

执行：

14. 如果 sql 语句中出现’<’的解决方案

1、使用 xml 中的字符实体

因为业务，需要在 mybatis 中，使用到大于号，小于号，所以就在 SQL 中直接使用了。
SELECT * FROM test WHERE 1 = 1 AND start_date <= CURRENT_DATE AND end_date >= CURRENT_DATE
可是，在执行时，总报错误：

Error creating document instance. Cause: org.xml.sax.SAXParseException; lineNumber: 74; columnNumber: 17;

元素内容必须由格式正确的字符数据或标记组成。
把AND start_date >= CURRENT_DATE AND end_date <= CURRENT_DATE去掉，就没有问题，所以确定是因为大于号，小于号引起的问题。

于是就想到了特殊符号，于是用了转义字符把 > 和 < 替换掉，然后就没有问题了。
SELECT * FROM test WHERE 1 = 1 AND start_date &lt;= CURRENT_DATE AND end_date &gt;= CURRENT_DATE
案例：

1.<if test="startDateTime!=null"> and mm.ttime &gt; to_date(#{startDateTime},'yyyy-mm-dd hh24:mi:ss')</if>  
2.<if test="endDateTime!=null"> and mm.ttime &lt;= to_date(#{endDateTime},'yyyy-mm-dd hh24:mi:ss')</if>

2、使用<![CDATA[ < ]]>

案例 1：

1.<![CDATA[ 
2.       and mm.ttime > to_date(#{startDateTime},'yyyy-mm-dd hh24:mi:ss') 
3.       and mm.ttime <= to_date(#{endDateTime},'yyyy-mm-dd hh24:mi:ss') 
4.]]>

案例 2：

mapper 文件示例代码 ：

and (t1.status <![CDATA[ >= ]]> 1  and  t1.status <![CDATA[ <= ]]> 2)
上述代码其实对应的sql：
and (t1.status > =1 andt1.status <= 2)

注意：

使用标记的 sql 语句中的 等标签不会被解析。

15.Spring 集成 Mybatis

15.1 引入 spring 和 Mybatis 相关依赖

pom.xml

<!-- 数据库连接池 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.8</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>1.2.2</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>4.1.3.RELEASE</version>
</dependency>
<!--spring 集成 Junit 测试 -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>4.1.3.RELEASE</version>
    <scope>test</scope>
</dependency>
<!--spring 容器 -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.1.3.RELEASE</version>
</dependency>

15.2 配置 spring 配置文件

applicationContext-dao.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
   http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
   http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">

<span class="hljs-comment">&lt;!-- 加载配置文件 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">context:property-placeholder</span> <span class="hljs-attr">location</span>=<span class="hljs-string">"classpath:properties/*.properties"</span>/&gt;</span>
<span class="hljs-comment">&lt;!-- 数据库连接池 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">bean</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"dataSource"</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"com.alibaba.druid.pool.DruidDataSource"</span>
      <span class="hljs-attr">destroy-method</span>=<span class="hljs-string">"close"</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"driverClassName"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.driver}"</span>/&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"url"</span>
              <span class="hljs-attr">value</span>=<span class="hljs-string">"jdbc:mysql://${jdbc.host}:3306/${jdbc.database}?useUnicode=true<span class="hljs-symbol">&amp;amp;</span>characterEncoding=utf-8<span class="hljs-symbol">&amp;amp;</span>zeroDateTimeBehavior=convertToNull"</span>/&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"username"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.userName}"</span>/&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"password"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.passWord}"</span>/&gt;</span>
    <span class="hljs-comment">&lt;!-- 初始化连接大小 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"initialSize"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.initialSize}"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
    <span class="hljs-comment">&lt;!-- 连接池最大数据库连接数  0 为没有限制 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"maxActive"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.maxActive}"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
    <span class="hljs-comment">&lt;!-- 连接池最大的空闲连接数，这里取值为20，表示即使没有数据库连接时依然可以保持20空闲的连接，而不被清除，随时处于待命状态 0 为没有限制 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"maxIdle"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.maxIdle}"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
    <span class="hljs-comment">&lt;!-- 连接池最小空闲 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"minIdle"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.minIdle}"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
    <span class="hljs-comment">&lt;!--最大建立连接等待时间。如果超过此时间将接到异常。设为-1表示无限制--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"maxWait"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${jdbc.maxWait}"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">bean</span>&gt;</span>

<span class="hljs-comment">&lt;!-- spring和MyBatis完美整合 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">bean</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"sqlSessionFactory"</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"org.mybatis.spring.SqlSessionFactoryBean"</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"dataSource"</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"dataSource"</span>/&gt;</span>
    <span class="hljs-comment">&lt;!-- 自动扫描mapping.xml文件 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"mapperLocations"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"classpath:mappers/*.xml"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
    <span class="hljs-comment">&lt;!--如果mybatis-config.xml没有特殊配置也可以不需要下面的配置--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"configLocation"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"classpath:mybatis-config.xml"</span> /&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">bean</span>&gt;</span>

<span class="hljs-comment">&lt;!-- DAO接口所在包名，Spring会自动查找其下的类 --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">bean</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"org.mybatis.spring.mapper.MapperScannerConfigurer"</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"basePackage"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"com.zpc.mybatis.dao"</span>/&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"sqlSessionFactoryBeanName"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"sqlSessionFactory"</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">property</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">bean</span>&gt;</span>

<span class="hljs-comment">&lt;!-- (事务管理)transaction manager --&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">bean</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"transactionManager"</span>
      <span class="hljs-attr">class</span>=<span class="hljs-string">"org.springframework.jdbc.datasource.DataSourceTransactionManager"</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"dataSource"</span> <span class="hljs-attr">ref</span>=<span class="hljs-string">"dataSource"</span>/&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">bean</span>&gt;</span>



</beans>

db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.host=localhost
jdbc.database=ssmdemo
jdbc.userName=root
jdbc.passWord=123456
jdbc.initialSize=0
jdbc.maxActive=20
jdbc.maxIdle=20
jdbc.minIdle=1
jdbc.maxWait=1000

由于 applicationContext-dao.xml 中配置了 Mapper 接口扫描，所以删除 mybatis-config.xml 中的配置，否则报已映射错误：
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for MyMapper.selectUser
删除 mybatis-config.xml 中的映射配置：

<!--<mappers>-->
    <!--<mapper resource="mappers/MyMapper.xml"/>-->
    <!--<mapper resource="mappers/UserDaoMapper.xml"/>-->
    <!--<mapper resource="mappers/UserMapper.xml"/>-->
    <!--<mapper resource="mappers/OrderMapper.xml"/>-->
<!--</mappers>-->

或者在构建 sqlSessionFactory 时不配置 mybatis-config.xml 也行：

<!-- spring 和 MyBatis 完美整合 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <!-- 自动扫描 mapping.xml 文件 -->
    <property name="mapperLocations" value="classpath:mappers/*.xml"></property>
    <!-- 如果 mybatis-config.xml 没有特殊配置也可以不需要下面的配置 -->
    <!--<property name="configLocation" value="classpath:mybatis-config.xml" />-->
</bean>

15.3 测试

UserMapperSpringTest.java

import com.zpc.mybatis.dao.UserMapper;
import com.zpc.mybatis.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

// 目标：测试一下 spring 的 bean 的某些功能
@RunWith(SpringJUnit4ClassRunner.class)//junit 整合 spring 的测试 // 立马开启了 spring 的注解
@ContextConfiguration(locations="classpath:spring/applicationContext-*.xml")// 加载核心配置文件，自动构建 spring 容器
public class UserMapperSpringTest {


<span class="hljs-meta">@Autowired</span>
<span class="hljs-keyword">private</span> UserMapper userMapper;

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserByTableName</span><span class="hljs-params">()</span> {
    List&lt;User&gt; userList = <span class="hljs-built_in">this</span>.userMapper.queryUserByTableName(<span class="hljs-string">"tb_user"</span>);
    <span class="hljs-keyword">for</span> (User user : userList) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testLogin</span><span class="hljs-params">()</span> {
    System.out.println(<span class="hljs-built_in">this</span>.userMapper.login(<span class="hljs-string">"hj"</span>, <span class="hljs-string">"123456"</span>));
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserById</span><span class="hljs-params">()</span> {
    System.out.println(<span class="hljs-built_in">this</span>.userMapper.queryUserById(<span class="hljs-string">"1"</span>));
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setName(<span class="hljs-string">"美女"</span>);
    user.setId(<span class="hljs-string">"1"</span>);
    userMapper.updateUser(user);

    System.out.println(<span class="hljs-built_in">this</span>.userMapper.queryUserById(<span class="hljs-string">"1"</span>));
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testQueryUserAll</span><span class="hljs-params">()</span> {
    List&lt;User&gt; userList = <span class="hljs-built_in">this</span>.userMapper.queryUserAll();
    <span class="hljs-keyword">for</span> (User user : userList) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testInsertUser</span><span class="hljs-params">()</span> {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setAge(<span class="hljs-number">20</span>);
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());
    user.setName(<span class="hljs-string">"大神"</span>);
    user.setPassword(<span class="hljs-string">"123456"</span>);
    user.setSex(<span class="hljs-number">2</span>);
    user.setUserName(<span class="hljs-string">"bigGod222"</span>);
    <span class="hljs-built_in">this</span>.userMapper.insertUser(user);
    System.out.println(user.getId());
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testUpdateUser</span><span class="hljs-params">()</span> {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    user.setBirthday(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());
    user.setName(<span class="hljs-string">"静静"</span>);
    user.setPassword(<span class="hljs-string">"123456"</span>);
    user.setSex(<span class="hljs-number">0</span>);
    user.setUserName(<span class="hljs-string">"Jinjin"</span>);
    user.setId(<span class="hljs-string">"1"</span>);
    <span class="hljs-built_in">this</span>.userMapper.updateUser(user);
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testDeleteUserById</span><span class="hljs-params">()</span> {
    <span class="hljs-built_in">this</span>.userMapper.deleteUserById(<span class="hljs-string">"1"</span>);
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">testqueryUserList</span><span class="hljs-params">()</span> {
    List&lt;User&gt; users = <span class="hljs-built_in">this</span>.userMapper.queryUserList(<span class="hljs-literal">null</span>);
    <span class="hljs-keyword">for</span> (User user : users) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">queryUserListByNameAndAge</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    List&lt;User&gt; users = <span class="hljs-built_in">this</span>.userMapper.queryUserListByNameAndAge(<span class="hljs-string">"鹏程"</span>, <span class="hljs-number">20</span>);
    <span class="hljs-keyword">for</span> (User user : users) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">queryUserListByNameOrAge</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    List&lt;User&gt; users = <span class="hljs-built_in">this</span>.userMapper.queryUserListByNameOrAge(<span class="hljs-literal">null</span>, <span class="hljs-number">16</span>);
    <span class="hljs-keyword">for</span> (User user : users) {
        System.out.println(user);
    }
}

<span class="hljs-meta">@Test</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">queryUserListByIds</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> Exception {
    List&lt;User&gt; users = <span class="hljs-built_in">this</span>.userMapper.queryUserListByIds(<span class="hljs-keyword">new</span> <span class="hljs-title class_">String</span>[]{<span class="hljs-string">"5"</span>, <span class="hljs-string">"2"</span>});
    <span class="hljs-keyword">for</span> (User user : users) {
        System.out.println(user);
    }
}

目录结构：

16.SpringBoot 集成 Mybatis

请参见博文：https://blog.csdn.net/hellozpc/article/details/82531834

17.Mybatis Generator 的使用

MyBatis Generator（MBG）是 MyBatis 和 iBATIS 的代码生成器。可以生成简单 CRUD 操作的 XML 配置文件、Mapper 文件 (DAO 接口)、实体类。实际开发中能够有效减少程序员的工作量，甚至不用程序员手动写 sql。
mybatis-generator 有多种用法：命令行、maven 插件等。命令行方式通常要把相关 jar 包下载到本地，再使用 java -jar 运行。方便起见，本文演示使用 maven 插件的方式。

1. 新建一个 Maven 项目 (可以直接建立一个初始的 springboot 项目)

pom 文件引入 mybatis-generator-maven-plugin

``` org.mybatis.generator mybatis-generator-maven-plugin 1.3.5 ```

2. 将插件需要的配置文件拷入到 resource 目录下，并做配置

generator.properties：配置数据库信息, 在 generatorConfig.xml 使用：

#generatorConfig Info
generator.location=D:\\software\\maven\\apache-maven-3.3.9\\repository\\mysql\\mysql-connector-java\\5.1.32\\mysql-connector-java-5.1.32.jar
generator.targetPackage=com.zpc.videoshow.generated
#gererator.schema=oracle-schema
gererator.tableName=video_info
gererator.domainObjectName=VideoInfo

jdbc.driver=com.mysql.jdbc.Driver
jdbc.host=jdbc:mysql://localhost:3306/videoshow
jdbc.userName=root
jdbc.passWord=123456
jdbc.initialSize=0
jdbc.maxActive=20
jdbc.maxIdle=20
jdbc.minIdle=1
jdbc.maxWait=1000

generatorConfig.xml：配置 generator 插件运行需要的参数信息

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <!-- 引入配置文件 -->
    <properties resource="generator.properties"/>
    <!-- 数据库驱动包位置, 路径请不要有中文 -->
    <!-- <classPathEntry location="D:\software\lib\mysql-connector-java-5.1.21.jar" /> -->
    <classPathEntry location="${generator.location}"/>
    <!-- 一个数据库一个 context-->
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <!-- 生成的 pojo，将 implements Serializable -->
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin"></plugin>

    <span class="hljs-comment">&lt;!-- 注释 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">commentGenerator</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"suppressAllComments"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"true"</span>/&gt;</span><span class="hljs-comment">&lt;!-- 是否取消注释 --&gt;</span>
        <span class="hljs-comment">&lt;!-- &lt;property name="suppressDate" value="true" /&gt;  是否生成注释代时间戳 --&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">commentGenerator</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- 数据库链接URL、用户名、密码 --&gt;</span>
    <span class="hljs-comment">&lt;!-- &lt;jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost:3306/sy" userId="sypro" password="sypro"&gt; --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">jdbcConnection</span> <span class="hljs-attr">driverClass</span>=<span class="hljs-string">"${jdbc.driver}"</span> <span class="hljs-attr">connectionURL</span>=<span class="hljs-string">"${jdbc.host}"</span> <span class="hljs-attr">userId</span>=<span class="hljs-string">"${jdbc.userName}"</span>
                    <span class="hljs-attr">password</span>=<span class="hljs-string">"${jdbc.passWord}"</span>&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">jdbcConnection</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- 类型转换 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">javaTypeResolver</span>&gt;</span>
        <span class="hljs-comment">&lt;!-- 默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer true，把JDBC DECIMAL
            和 NUMERIC 类型解析为java.math.BigDecimal --&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"forceBigDecimals"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"false"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">javaTypeResolver</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- 生成model模型，设置对应的包名(targetPackage)和存放路径(targetProject)。targetProject可以指定具体的路径,如./src/main/java,也可以使用MAVEN来自动生成,这样生成的代码会在target/generatord-source目录下 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">javaModelGenerator</span> <span class="hljs-attr">targetPackage</span>=<span class="hljs-string">"${generator.targetPackage}"</span> <span class="hljs-attr">targetProject</span>=<span class="hljs-string">"./src/main/java"</span>&gt;</span>
        <span class="hljs-comment">&lt;!-- 是否在当前路径下新加一层schema,eg：false路径com.oop.eksp.user.model 而true:com.oop.eksp.user.model.[schemaName] --&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"enableSubPackages"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"false"</span>/&gt;</span>
        <span class="hljs-comment">&lt;!-- 从数据库返回的值被清理前后的空格 --&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"trimStrings"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"true"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">javaModelGenerator</span>&gt;</span>

    <span class="hljs-comment">&lt;!--对应的mapper.xml文件 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">sqlMapGenerator</span> <span class="hljs-attr">targetPackage</span>=<span class="hljs-string">"${generator.targetPackage}"</span> <span class="hljs-attr">targetProject</span>=<span class="hljs-string">"./src/main/java"</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"enableSubPackages"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"true"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">sqlMapGenerator</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- 对应的Mapper接口类文件 --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">javaClientGenerator</span> <span class="hljs-attr">type</span>=<span class="hljs-string">"XMLMAPPER"</span> <span class="hljs-attr">targetPackage</span>=<span class="hljs-string">"${generator.targetPackage}"</span>
                         <span class="hljs-attr">targetProject</span>=<span class="hljs-string">"./src/main/java"</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"enableSubPackages"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"true"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">javaClientGenerator</span>&gt;</span>

    <span class="hljs-comment">&lt;!-- 列出要生成代码的所有表，这里配置的是不生成Example文件 --&gt;</span>
    <span class="hljs-comment">&lt;!-- schema即为数据库名tableName为对应的数据库表 domainObjectName是要生成的实体类 enable*ByExample是否生成 example类   --&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">table</span> <span class="hljs-attr">tableName</span>=<span class="hljs-string">"${gererator.tableName}"</span> <span class="hljs-attr">domainObjectName</span>=<span class="hljs-string">"${gererator.domainObjectName}"</span>
           <span class="hljs-attr">schema</span>=<span class="hljs-string">"${gererator.schema}"</span>
           <span class="hljs-attr">enableCountByExample</span>=<span class="hljs-string">"false"</span> <span class="hljs-attr">enableUpdateByExample</span>=<span class="hljs-string">"false"</span>
           <span class="hljs-attr">enableDeleteByExample</span>=<span class="hljs-string">"false"</span> <span class="hljs-attr">enableSelectByExample</span>=<span class="hljs-string">"false"</span>
           <span class="hljs-attr">selectByExampleQueryId</span>=<span class="hljs-string">"false"</span>&gt;</span>
        <span class="hljs-comment">&lt;!-- 忽略列，不生成bean 字段
        &lt;ignoreColumn column="FRED" /&gt;--&gt;</span>
        <span class="hljs-comment">&lt;!-- 指定列的java数据类型
        &lt;columnOverride column="LONG_VARCHAR_FIELD" jdbcType="VARCHAR" /&gt;  --&gt;</span>
        <span class="hljs-comment">&lt;!-- 用于指定生成实体类时是否使用实际的列名作为实体类的属性名。false是 Camel Case风格--&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"useActualColumnNames"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"false"</span>/&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">table</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">context</span>&gt;</span>



</generatorConfiguration>

3. 运行 generator 插件（确保数据库已经运行）

  • 方法 1：直接找到 mybatis-generator 的插件，右击运行。
  • 方法 2：在运行配置里面添加 maven 命令

4. 查看生成的文件

5. 一些小技巧

  • a) 建表时，字段名称建议用 "_" 分隔多个单词，比如:AWB_NO、REC_ID…，这样生成的 entity，属性名称就会变成漂亮的驼峰命名，即：awbNo、recId

  • b)oracle 中，数值形的字段，如果指定精度，比如 Number(16,2)，默认生成 entity 属性是 BigDecimal 型 ，如果不指定精度，比如:Number(8)，指默认生成的是 Long 型

  • c)oracle 中的 nvarchar/nvarchar2，mybatis-generator 会识别成 Object 型，建议不要用 nvarchar2，改用 varchar2

6.Example 文件的使用

用过 Hibernate 的同学一定感叹于其完全不用手动写 sql 的强大功能，其实 Mybatis 也可以配置生成 Example，省去一些简单的 sql 编写，实际开发中也会带来方便。

  • a. 修改 generatorConfig.xml 的配置：
 enableCountByExample="true" enableUpdateByExample="true"
 enableDeleteByExample="true" enableSelectByExample="true"
 selectByExampleQueryId="true"
  • b.pom 中引入 mybatis 的依赖：
<dependency>
   <groupId>org.mybatis</groupId>
   <artifactId>mybatis</artifactId>
   <version>3.4.1</version>
</dependency>
  • c. 运行 generator

这种情况下多生成了一个 Example 的文件，Mapper 文件的内容也会多很多 example 相关的：

Example 的详细使用百度之，参见：
https://blog.csdn.net/m0_37795198/article/details/78848045

18.MyBatis 整合分页插件 pageHelper

请参见博文：https://blog.csdn.net/hellozpc/article/details/82531834