mybatis-210720-03---映射文件_select_resultMap_分步查询传递多列值&fetchType

mybatis-210720-03—映射文件_select_resultMap_分步查询传递多列值&fetchType.md

• DepartmentMapper.java
• DepartmentMapper.xml(笔记在这儿)
• EmployeeMapper.java
• EmployeeMapper.xml
• MybatisTest.java

---

<!--
		场景2
			查询部门的时候，把对应所有的员工信息查询出来
-->

DepartmentMapper.java

package com.bgy.mybatis.dao;
import com.bgy.mybatis.bean.Department;

public interface DepartmentMapper {
	
	public Department getDeptByIdStep(Integer id);
}

---

DepartmentMapper.xml(笔记在这儿)

<?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.bgy.mybatis.dao.DepartmentMapper">
	
	<!--
		场景2
			查询部门的时候，把对应所有的员工信息查询出来
	-->
	<resultMap type="com.bgy.mybatis.bean.Department" id="MyDeptStep">
		<id column="id" property="id"/>
		<result column="dept_name" property="departmentName"/>
		
		<!--
		多列值传递过去
		将多列的值封装map传递
		column="{key1=column1,key2=column2}"
		
		fetchType：使用延迟加载
			lazy：延迟加载
			eager：立即加载
		-->
		<!--
			这个emps是我们Department中的属性
			column="id"> 中的id就把，把哪个属性传给这个查询方法
			column="{deptId=id}">
		-->
		<collection property="emps"
			select="com.bgy.mybatis.dao.EmployeeMapper.getEmpsByDeptId"
			column="{deptId=id}"
			fetchType="lazy">
		</collection>
	</resultMap>
	<select id="getDeptByIdStep" resultMap="MyDeptStep">
		select 
			id,dept_name
		from 
			tbl_dept
		where
			id=#{id}
	</select>
</mapper>

---

EmployeeMapper.java

package com.bgy.mybatis.dao;

import java.util.List;
import com.bgy.mybatis.bean.Employee;

public interface EmployeeMapper {
	
	public List<Employee> getEmpsByDeptId(Integer deptId);
}

---

EmployeeMapper.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.bgy.mybatis.dao.EmployeeMapper">
	
	<!--
		场景2
			查询部门的时候，把对应所有的员工信息查询出来
	-->
	<select id="getEmpsByDeptId" resultType="com.bgy.mybatis.bean.Employee">
		select 
			* 
		from
			tbl_employee
		where 	
			d_id=#{deptId} 
	</select>
</mapper>

---

MybatisTest.java

package com.bgy.mybatis.test;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.jupiter.api.Test;

import com.bgy.mybatis.bean.Department;
import com.bgy.mybatis.dao.DepartmentMapper;

class MybatisTest {
	
	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}

	
	/**
	 * 测试分步查询传递多列值&fetchType
	 * @throws IOException
	 */
	@Test
	public void test04() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession sqlSession = sqlSessionFactory.openSession();
		
		try {
			DepartmentMapper mapper = sqlSession.getMapper(DepartmentMapper.class);
			Department department = mapper.getDeptByIdStep(1);
			
			System.out.println(department.getDepartmentName());
//			System.out.println(department.getEmps());
		} finally {
			sqlSession.close();
		}
	}
}