Employee.java
public class Employee { private Integer id; String lastName; String gender; String email; Department dept; }
Department.java
Department { String deptName; private List<Employee> employee; }
DepartmentMapper.java
interface DepartmentMapper { public Department getDeptByIdWithAllEmployees(Integer id); }
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.gong.mybatis.dao.DepartmentMapper"> resultMap type="com.gong.mybatis.bean.Department" id="MyDept"> id column="did" property="id"/> result ="dept_name"="deptName"collection property="employee" ofType="com.gong.mybatis.bean.Employee"> ="eid"/> ="last_name"="lastName"="gender"="gender"="email"="email"</collection> resultMapselect id="getDeptByIdWithAllEmployees" resultMap> SELECT d.id did,d.dept_name,e.id eid,e.last_name,e.gender,e.email from tbl_department d LEFT JOIN tbl_employee e on d.id = e.d_id WHERE d.id = #{id} select> mapper>
说明:这实际上是多对一查询,即一个部门里面有多个员工。collection标签中property属性标识Department类中的成员属性,ofType标识其类型。
对该功能进行测试:
package com.gong.mybatis.test; import java.io.IOException; java.io.InputStream; java.util.List; java.util.Map; org.apache.ibatis.io.Resources; org.apache.ibatis.session.SqlSession; org.apache.ibatis.session.SqlSessionFactory; org.apache.ibatis.session.SqlSessionFactoryBuilder; org.junit.Test; com.gong.mybatis.bean.Department; com.gong.mybatis.bean.Employee; com.gong.mybatis.dao.DepartmentMapper; com.gong.mybatis.dao.EmployeeMapperPlus; TestMybatis2 { public SqlSessionFactory getSqlSessionFactory() throws IOException { String resource = "mybatis-config.xml"; InputStream is = Resources.getResourceAsStream(resource); return new SqlSessionFactoryBuilder().build(is); } @Test void test2() IOException { SqlSessionFactory sqlSessionFactory = getSqlSessionFactory(); SqlSession openSession = sqlSessionFactory.openSession(); try { DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.); Department department = mapper.getDepthByIdWithAllEmployees(1); System.out.println(department); System.out.println(department.getEmployee()); openSession.commit(); } finally { openSession.close(); } } }
输出:
DEBUG 01-20 19:13:24,335 ==> Preparing: SELECT d.id did,e.email from tbl_department d LEFT JOIN tbl_employee e on d.id = e.d_id WHERE d.id = ? (BaseJdbcLogger.java:145)
DEBUG 01-20 19:13:24,389 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:145)
DEBUG 01-20 19:13:24,426 <== Total: 2 (BaseJdbcLogger.java:145)
Department [id=1,deptName=开发部]
[Employee [id=1,lastName=xiximayou,gender=1,email=xiximayou@qq.com,dept=null],Employee [id=3,lastName=小红,gender=0,email=xiaohong@qq.com,dept=null]]
可以看到对于一个部门,取得了里面的雇员,表明该功能是成功的。