MyBatis总结(二十二)--MyBatis_映射文件_select_resultMap_关联查询_association定义关联对象封装规则

浅浅的花香味﹌ 2022-05-12 08:06 197阅读 0赞

本文内容来自尚硅谷[任务31：MyBatis\_映射文件\_select\_resultMap\_关联查询\_association定义关联对象封装规则][31_MyBatis_select_resultMap_association]

本文介绍了association的基本使用方法下面就是具体的代码

本文代码可以基于[MyBatis总结(二)--helloworld][MyBatis_--helloworld]代码

Junit代码

@Test
    	public void test05() throws IOException{
    		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
    		SqlSession openSession = sqlSessionFactory.openSession();
    		try{
    			EmployeeMapperPlus mapper = openSession.getMapper(EmployeeMapperPlus.class);
    			Employee empAndDept = mapper.getEmpAndDept(1);
    			System.out.println(empAndDept);
    			System.out.println(empAndDept.getDept());
    		}finally{
    			openSession.close();
    		}
    	}

EmployeeMapperPlus

package com.atguigu.mybatis.dao;
    
    import java.util.List;
    
    import com.atguigu.mybatis.bean.Employee;
    
    public interface EmployeeMapperPlus {
    	
    	public Employee getEmpById(Integer id);
    	
    	public Employee getEmpAndDept(Integer id);
    	
    	public Employee getEmpByIdStep(Integer id);
    	
    	public List<Employee> getEmpsByDeptId(Integer deptId);
    
    }

xml

<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyDifEmp2">
    		<id column="id" property="id"/>
    		<result column="last_name" property="lastName"/>
    		<result column="gender" property="gender"/>
    
    		
    		<association property="dept" javaType="com.atguigu.mybatis.bean.Department">
    			<id column="did" property="id"/>
    			<result column="dept_name" property="departmentName"/>
    		</association>
    	</resultMap>
    	
    	<select id="getEmpAndDept" resultMap="MyDifEmp">
    		SELECT e.id id,e.last_name last_name,e.gender gender,e.d_id d_id,
    		d.id did,d.dept_name dept_name FROM tbl_employee e,tbl_dept d
    		WHERE e.d_id=d.id AND e.id=#{id}
    	</select>

请注意xml中的注释

[31_MyBatis_select_resultMap_association]: http://www.gulixueyuan.com/course/43/task/1180/show
[MyBatis_--helloworld]: https://blog.csdn.net/lsx2017/article/details/82493457