日常报错记录2： MyBatis：DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.------------ Cause: java.lang.NoSuchMethodException: com.offcn.dao.ShopDao.<init>()
直接上干货：
报错归纳 1：
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
原因：xml 里面不能有 java 方不存在的类，它是会去找的，找不到就报错，所以，万一删掉 java 类了，xml 里面的相对应映射的字段也要注释掉。遇到两次了！浪费不少时间！
2.MyBatis 他要加空构造 实例化对象
原因：MyBitis ，他实体类 pojo class 里 要加空构造
3. 写法
class 是点，路径是斜杠
4.
xml 控制多级级联查数据库，是可以的，（MyBatis xml 作为实现 数据库查询），我这里四级连着查询
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.XXXX.dao.ShopDao"><!--private int sid;
private String sname;private List</span><span style="color: rgba(128, 128, 128, 1)"><</span>Book<span style="color: rgba(128, 128, 128, 1)">></span> blist;<span style="color: rgba(0, 128, 128, 1)">--</span><span style="color: rgba(0, 128, 128, 1)">></span><resultMap id="resultMap_shop" type="shop">
<span style="color: rgba(128, 128, 128, 1)"><</span>id property<span style="color: rgba(128, 128, 128, 1)">=</span>"sid" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"sid"<span style="color: rgba(128, 128, 128, 1)">></</span>id<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"sname" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"sname" <span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>collection property<span style="color: rgba(128, 128, 128, 1)">=</span>"blist" ofType<span style="color: rgba(128, 128, 128, 1)">=</span>"book"<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>id property<span style="color: rgba(128, 128, 128, 1)">=</span>"bid" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"bid"<span style="color: rgba(128, 128, 128, 1)">></</span>id<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"bname" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"bname"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>association property<span style="color: rgba(128, 128, 128, 1)">=</span>"<span style="color: rgba(255, 0, 255, 1)">user</span>" javaType<span style="color: rgba(128, 128, 128, 1)">=</span>"<span style="color: rgba(255, 0, 255, 1)">user</span>"<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>id property<span style="color: rgba(128, 128, 128, 1)">=</span>"uid" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"uid"<span style="color: rgba(128, 128, 128, 1)">></</span>id<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"uname" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"uname"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"password" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"password"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>association property<span style="color: rgba(128, 128, 128, 1)">=</span>"p" javaType<span style="color: rgba(128, 128, 128, 1)">=</span>"person" <span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>id property<span style="color: rgba(128, 128, 128, 1)">=</span>"pid" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"pid"<span style="color: rgba(128, 128, 128, 1)">></</span>id<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"pname" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"pname"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"sex" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"sex"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"><</span>result property<span style="color: rgba(128, 128, 128, 1)">=</span>"birthday" <span style="color: rgba(0, 0, 255, 1)">column</span><span style="color: rgba(128, 128, 128, 1)">=</span>"birthday"<span style="color: rgba(128, 128, 128, 1)">></</span>result<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"></</span>association<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"></</span>association<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(128, 128, 128, 1)"></</span>collection<span style="color: rgba(128, 128, 128, 1)">></span><!-- <association property="blist" javaType=""-->
</resultMap><!-- List<Shop> getAll(int sid);-->
<span style="color: rgba(128, 128, 128, 1)"><</span><span style="color: rgba(0, 0, 255, 1)">select</span> id<span style="color: rgba(128, 128, 128, 1)">=</span>"getAll" parameterType<span style="color: rgba(128, 128, 128, 1)">=</span>"<span style="color: rgba(0, 0, 255, 1)">int</span>" resultMap<span style="color: rgba(128, 128, 128, 1)">=</span>"resultMap_shop"<span style="color: rgba(128, 128, 128, 1)">></span> <span style="color: rgba(0, 0, 255, 1)">select</span> <span style="color: rgba(0, 0, 255, 1)">from</span> t_shop s,t_book b,t_user u,t_person p <span style="color: rgba(0, 0, 255, 1)">where</span> u.user_person_fk<span style="color: rgba(128, 128, 128, 1)">=</span>p.pid <span style="color: rgba(128, 128, 128, 1)">and</span> b.book_user_fk<span style="color: rgba(128, 128, 128, 1)">=</span>u.uid <span style="color: rgba(128, 128, 128, 1)">and</span> s.sid<span style="color: rgba(128, 128, 128, 1)">=</span><span style="color: rgba(0, 0, 0, 1)">#{sid} </span><span style="color: rgba(128, 128, 128, 1)"></</span><span style="color: rgba(0, 0, 255, 1)">select</span><span style="color: rgba(128, 128, 128, 1)">></span></mapper>
5.
Cause: java.lang.NoSuchMethodException: com.offcn.dao.ShopDao.<init>()，其实是缺少构造，但构造没问题，之后发现是这个写错