标签：pac res ati pre 还需要 iat 映射文件 height png
a) 数据库表的设计
学生表student与老师表teacher
b) 实体类
c）编写映射文件student.mapper.xml
第一种方式：按结果嵌套处理
<?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="cn.sxt.entity.student.mapper"> <!-- 对于多对一处理有两种方式1、按结果嵌套处理2、按查询嵌套处理 --> <select id="getStudents" resultMap="StudentTeacher"> select s.id sid,s.name sname,s.tid stid,t.id tid,t.name tname from student s,teacher t where s.tid = t.id </select> <resultMap type="Student" id="StudentTeacher">重点在这一块 <id column="sid" property="id"/> <result column="sname" property="name"/> <association property="teacher" javaType="Teacher"> <id column="tid" property="id"/> <result column="tname" property="name"/> </association> </resultMap> </mapper>
第二种方式：按查询嵌套处理，有两种写法（这种方式相当于做了两次查询）
这种方式student.mapper.xml配置文件代码如下
<?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="cn.sxt.entity.student.mapper"> <!-- 对于多对一处理有两种方式1、按结果嵌套处理2、按查询嵌套处理 <select id="getStudents" resultMap="StudentTeacher"> select s.id sid,s.name sname,s.tid stid,t.id tid,t.name tname from student s,teacher t where s.tid = t.id </select> <resultMap type="Student" id="StudentTeacher"> <id column="sid" property="id"/> <result column="sname" property="name"/> <association property="teacher" javaType="Teacher"> <id column="tid" property="id"/> <result column="tname" property="name"/> </association> </resultMap> --> <select id="getStudents" resultMap="StudentTeacher"> select * from student </select> <resultMap type="Student" id="StudentTeacher"> <association property="teacher" column="tid" javaType="Teacher" select="cn.sxt.entity.teacher.mapper.getTeacher"></association> </resultMap> </mapper>
teacher.mapper.xml配置文件代码如下
<?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="cn.sxt.entity.teacher.mapper"> <select id="getTeacher" resultType="Teacher"> select * from teacher where id=#{id} </select> </mapper>
另外还需要在mybatis.cfg.xml中添加配置
然后在mybatis.cfg.xml配置文件里面只写一个
标签：pac res ati pre 还需要 iat 映射文件 height png
原文地址：https://www.cnblogs.com/djlindex/p/11386306.html
