MyBatis总结(二十三)--任务32：MyBatis_映射文件_select_resultMap_关联查询_association分步查询

超、凢脫俗 2022-05-12 08:08 222阅读 0赞

与[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][MyBatis_--MyBatis_select_resultMap_association]相比较，本文注重的是分部查询（及执行两次sql语句）。

Junit代码

@Test
    	public void test05() throws IOException{
    		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
    		SqlSession openSession = sqlSessionFactory.openSession();
    		try{
    			EmployeeMapperPlus mapper = openSession.getMapper(EmployeeMapperPlus.class);
    			Employee employee = mapper.getEmpByIdStep(3);
    			System.out.println(employee);
    			System.out.println(employee.getDept());
    		}finally{
    			openSession.close();
    		}
    
    
    	}

com.atguigu.mybatis.dao.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);
    
    }

conf/com/atguigu/mybatis/dao/EmployeeMapperPlus.xml

<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmpByStep">
    	 	<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.DepartmentMapper.getDeptById"
    	 		column="d_id">
     		</association>
    	 </resultMap>
    	 
    	 <select id="getEmpByIdStep" resultMap="MyEmpByStep">
    	 	select * from tbl_employee where id=#{id}
    	 	<if test="_parameter!=null">
    	 		and 1=1
    	 	</if>
    	 </select>

第二个sql的javabean

com.atguigu.mybatis.bean.Department

package com.atguigu.mybatis.bean;
    
    import java.util.List;
    
    public class Department {
    	
    	private Integer id;
    	private String departmentName;
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getDepartmentName() {
    		return departmentName;
    	}
    	public void setDepartmentName(String departmentName) {
    		this.departmentName = departmentName;
    	}
    
    	@Override
    	public String toString() {
    		return "Department{" +
    				"id=" + id +
    				", departmentName='" + departmentName + '\'' +
    				'}';
    	}
    }

第二个sql的dao

com.atguigu.mybatis.dao.DepartmentMapper

package com.atguigu.mybatis.dao;
    
    import com.atguigu.mybatis.bean.Department;
    
    public interface DepartmentMapper {
    	
    	public Department getDeptById(Integer id);
    	
    	public Department getDeptByIdPlus(Integer id);
    
    	public Department getDeptByIdStep(Integer id);
    }

第二个sql的xml

conf/com/atguigu/mybatis/dao/DepartmentMapper.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.DepartmentMapper">
    	
    	<select id="getDeptById" resultType="com.atguigu.mybatis.bean.Department">
    		select id,dept_name departmentName from tbl_dept where id=#{id}
    	</select>
    </mapper>

[MyBatis_--MyBatis_select_resultMap_association]: https://blog.csdn.net/lsx2017/article/details/82720972