Day21——MyBatis自定义映射 association 分步查询

r囧r小猫 2023-07-04 14:06 8阅读 0赞

# 一. 例子 #

DepartmentMapperResultMap.java

package com.atguigu.mybatis.dao;
    
    import com.atguigu.mybatis.beans.Department;
    
    public interface DepartmentMapperResultMap { 
    
    	
    	public Department selectDepartmentById(Integer id);
    }

DepartmentMapperResultMap.xml

<?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.atguigu.mybatis.dao.DepartmentMapperResultMap">
    	
    	
    	<select id="selectDepartmentById" resultType="com.atguigu.mybatis.beans.Department">
    	    select id, dept_name departmentName from tbl_dept where id = #{id}
    	</select>
    	
    	
    </mapper>

EmployeeMapperResultMap.xml

<select id="selectEmployeeAndDeptStep" resultMap="myEmpAndDeptStep">
    	   select id, last_name, email, gender, d_id from tbl_employee where id = #{id}
    	</select>
    	<resultMap type="com.atguigu.mybatis.beans.Employee" id="myEmpAndDeptStep">
    	     <id column="id" property="id"/>
    	     <result column="last_name" property="lastName"/>
    	     <result column="email" property="email"/>
    	     <result column="gender" property="gender"/>
    	     
    	     
    	     <association property="dept" select="com.atguigu.mybatis.dao.DepartmentMapperResultMap.selectDepartmentById" column="d_id" >
    	     </association>
    	     
    	     
    	</resultMap>

TestMyBatisResultMap.java

@Test
    	public void testResultMapAssociationStep() throws Exception { 
    		SqlSessionFactory ssf = getSqlSessionFactory();
    		SqlSession session = ssf.openSession();
    		
    		try { 
    			EmployeeMapperResultMap mapper = session.getMapper(EmployeeMapperResultMap.class);
    			Employee employee = mapper.selectEmployeeAndDeptStep(1001);
    			System.out.println(employee);
    			
    			
    			session.commit();
    		} finally { 
    			// TODO: handle finally clause
    			session.close();
    		}
    	}
    
    public SqlSessionFactory getSqlSessionFactory() throws Exception { 
    		String resource = "mybatis-config.xml"; 
    		InputStream inputStream = 
    				Resources.getResourceAsStream(resource); 
    		SqlSessionFactory sqlSessionFactory = 
    				new SqlSessionFactoryBuilder().build(inputStream);
    		return sqlSessionFactory;
    	}