13、mybatis多表关联查询级联属性

文章目录

• • • 1、创建表结构
    • 2、EmployeeMapper接口
    • 3、EmployeeMapper.xml
    • 4、Test

1、创建表结构

CREATE TABLE `mybatis`.`dept` (`id` INT NOT NULL ,`dept_name` VARCHAR(45) NULL ,PRIMARY KEY (`id`) );alter table employee add d_id INT(45);INSERT INTO `mybatis`.`dept` (`id`, `dept_name`) VALUES ('1', '开发部'); INSERT INTO `mybatis`.`dept` (`id`, `dept_name`) VALUES ('2', '测试部');

2、EmployeeMapper接口

package com.mi.dao;import com.mi.pojo.Employee; import org.apache.ibatis.annotations.MapKey; import org.apache.ibatis.annotations.Param;import java.util.List; import java.util.Map;public interface EmployeeMapper {//查询员工及部门public Employee getEmpAndDept(Integer id); }

3、EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!--指定为接口的全类名--> <mapper namespace="com.mi.dao.EmployeeMapper"><!--联合查询，级联属性封装结果集--><resultMap id="myEmpAndEmp" type="com.mi.pojo.Employee"><id column="id" property="id"/><result column="last_name" property="lastName"/><result column="gender" property="gender"/><result column="d_id" property="dept.id"/><result column="dept_name" property="dept.deptName"/></resultMap><!--关联查询员工及部门--><select id="getEmpAndDept" resultMap="myEmpAndEmp">select e.id,e.last_name, e.gender,d.id d_id,d.dept_name dept_namefrom employee e ,dept dwhere e.d_id = d.id and e.id = #{id}</select> </mapper>

4、Test

@Testpublic void getEmpAndDept() throws IOException {//1、获取SqlSessionFactory对象SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();//2、获取Sqlsesion对象SqlSession sqlSession = sqlSessionFactory.openSession();try {//3、获取接口的实现类对象//会为接口自动创建一个代理对象，代理对象去执行增删改查方法EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);Employee employee = mapper.getEmpAndDept(3);System.out.println(employee);System.out.println(employee.getDept());}finally {sqlSession.close();}}

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