鉴别器：mybatis可以使用discriminator判断某列的值，然后根据某列的值改变封装行为。

示例如下：

DeptmentMapper接口定义：

package com.mybatis.dao;

import com.mybatis.bean.Department;

public interface DeptmentMapper {

public Department getDeptById(Integer id);

}

DeptmentMapper.xml文件定义：

/p>

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

select id,dept_name departmentName from tbl_dept where id=#{id}

EmployeeMapper接口定义：

package com.mybatis.dao;

import com.mybatis.bean.Employee;

public interface EmployeeMapper {

public Employee getEmpByIdWithDept(Integer id);

}

EmployeeMapper.xml文件定义：

/p>

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

select="com.mybatis.dao.DeptmentMapper.getDeptById"

column="d_id">

select * from tbl_employee where id=#{id}

测试代码：

package com.mybatis.demo;

import com.mybatis.bean.Department;

import com.mybatis.bean.Employee;

import com.mybatis.dao.DeptmentMapper;

import com.mybatis.dao.EmployeeMapper;

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 java.io.IOException;

import java.io.InputStream;

public class MyTest {

public SqlSessionFactory getSqlSessionFactory() throws IOException {

String resource = "mybatis-config.xml";

InputStream inputStream = Resources.getResourceAsStream(resource);

return new SqlSessionFactoryBuilder().build(inputStream);

}

@Test

public void testResultMap() throws IOException {

SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

SqlSession openSession = sqlSessionFactory.openSession(true);

try {

EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

Employee girl = mapper.getEmpByIdWithDept(1);

System.out.println(girl.getDept());

Employee boy = mapper.getEmpByIdWithDept(7);

System.out.println(boy.getDept());

} finally {

openSession.close();

}

}

}