4_多对多关联查询
根据项目编号查询项目信息,以及参与到该项目之中的所有的员工信息
实体类
- @NoArgsConstructor
- @AllArgsConstructor
- @Data
- public class Project implements Serializable {
-
private Integer pid; -
private String pname; -
private Integer money; -
// 组合一个ProjectRecord对象集合作为属性 -
private List<ProjectRecord> projectRecords; - }
- @Data
- @AllArgsConstructor
- @NoArgsConstructor
- public class ProjectRecord implements Serializable {
-
private Integer empno; -
private Integer pid; -
// 组合一个Emp对象作为属性 -
private Emp emp; - }
接口
- package com.msb.mapper;
- import com.msb.pojo.Emp;
- import com.msb.pojo.Project;
- /**
-
- @Author: Ma HaiYang
-
- @Description: MircoMessage:Mark_7001
- */
- public interface ProjectMapper {
-
/** -
* 根据项目编号查询一个项目信息及参与该项目的所有员工信息 -
* @param pid 项目编号 -
* @return 所有信息封装的Project对象 -
*/ -
Project findProjectJoinEmpsByPid(int pid); - }
映射文件
-
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" -
"http://mybatis.org/dtd/mybatis-3-mapper.dtd"> -
-
<!--Project findProjectJoinEmpsByPid(int pid);--> -
<resultMap id="projectJoinEmps" type="project"> -
<id column="pid" property="pid"></id> -
<result column="pname" property="pname"></result> -
<result column="money" property="money"></result> -
<!--一对多 集合属性 collection--> -
<collection property="projectRecords" ofType="projectRecord"> -
<id column="empno" property="empno"></id> -
<id column="pid" property="pid"></id> -
<!--一对一 --> -
<association property="emp" javaType="emp"> -
<id property="empno" column="empno"></id> -
<result property="ename" column="ename"></result> -
<result property="job" column="job"></result> -
<result property="sal" column="sal"></result> -
<result property="hiredate" column="hiredate"></result> -
<result property="mgr" column="mgr"></result> -
<result property="comm" column="comm"></result> -
<result property="deptno" column="deptno"></result> -
</association> -
</collection> -
</resultMap> -
<select id="findProjectJoinEmpsByPid" resultMap="projectJoinEmps"> -
select * from -
project p -
left join projectrecord pr -
on p.pid = pr.pid -
left join emp e -
on e.empno = pr.empno -
where p.pid= #{pid} -
</select>
测试代码
- @Test
- public void testManyToMany() throws ParseException {
-
ProjectMapper mapper = sqlSession.getMapper(ProjectMapper.class); -
Project project = mapper.findProjectJoinEmpsByPid(2); -
System.out.println(project.getPid()); -
System.out.println(project.getPname()); -
System.out.println(project.getMoney()); -
List<ProjectRecord> projectRecords = project.getProjectRecords(); -
for (ProjectRecord projectRecord : projectRecords) { -
Emp emp = projectRecord.getEmp(); -
System.out.println(emp); -
} - }
标签：Project,mapper,pid,private,关联,project,emp,查询 From： https://www.cnblogs.com/01way/p/17592329.html