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]-Logginginitializedusing'classorg.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...

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<Book> blist;--><resultMap id="resultMap_shop" type="shop"> <id property="sid" column="sid"></id> <result property="sname" column="sname" ></result> <collection property="blist"  ofType="book">  <id property="bid" column="bid"></id>  <result property="bname" column="bname"></result><association property="user" javaType="user"> <id property="uid" column="uid"></id> <result property="uname" column="uname"></result> <result property="password" column="password"></result> <association property="p" javaType="person" >  <id property="pid" column="pid"></id>  <result property="pname" column="pname"></result>  <result property="sex" column="sex"></result>  <result property="birthday" column="birthday"></result> </association></association> </collection><!-- <association property="blist" javaType=""--></resultMap><!-- List<Shop> getAll(int sid);--> <select id="getAll" parameterType="int" resultMap="resultMap_shop">select from t_shop s,t_book b,t_user u,t_person p where u.user_person_fk=p.pid and b.book_user_fk=u.uid and s.sid=#{sid} </select></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

源文地址:http://www.guoxiongfei.cn/cntech/12291.html