mybatis文件映射之利用collection定义关联集合(五)
Employee.java
public class Employee {
private Integer id;
private String lastName;
private String gender;
private String email;
Department dept;
}
Department.java
public class Department {
private Integer id;
private String deptName;
private List<Employee> employee;
}
DepartmentMapper.java
public 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 column="dept_name" property="deptName"/>
<collection property="employee" ofType="com.gong.mybatis.bean.Employee">
<id column="eid" property="id"/>
<result column="last_name" property="lastName"/>
<result column="gender" property="gender"/>
<result column="email" property="email"/>
</collection>
</resultMap>
<select id="getDeptByIdWithAllEmployees" resultMap="MyDept">
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;
import java.io.InputStream;
import java.util.List;
import java.util.Map;
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.Test;
import com.gong.mybatis.bean.Department;
import com.gong.mybatis.bean.Employee;
import com.gong.mybatis.dao.DepartmentMapper;
import com.gong.mybatis.dao.EmployeeMapperPlus;
public class TestMybatis2 {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream is = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(is);
}
@Test
public void test2() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try {
DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.class);
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,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 = ? (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。
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