package com.test.mybatis;

public class Employee {

    private Integer id;

    private String lastName;

    private String email;

    private String gender;

    private Depart depart;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getLastName() {

        return lastName;

    }

    public void setLastName(String lastName) {

        this.lastName = lastName;

    }

    public String getEmail() {

        return email;

    }

    public void setEmail(String email) {

        this.email = email;

    }

    public String getGender() {

        return gender;

    }

    public void setGender(String gender) {

        this.gender = gender;

    }

    public Depart getDepart() {

        return depart;

    }

    public void setDepart(Depart depart) {

        this.depart = depart;

    }

    @Override

    public String toString() {

        return "Employee [id=" + id + ", lastName=" + lastName + ", email="

                + email + ", gender=" + gender + ", depart=" + depart + "]";

    }

}

package com.test.mybatis;

public class Depart {

    private int id;

    private String departName;

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getDepartName() {

        return departName;

    }

    public void setDepartName(String departName) {

        this.departName = departName;

    }

    @Override

    public String toString() {

        return "Depart [id=" + id + ", departName=" + departName + "]";

    }

}

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE configuration

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

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

    <configuration>

        <environments default="development">

            <environment id="development">

                <transactionManager type="JDBC"/>

                <dataSource type="POOLED">

                    <property name="driver" value="com.mysql.jdbc.Driver"/>

                    <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>

                    <property name="username" value="root"/>

                    <property name="password" value="root"/>

                </dataSource>

            </environment>

        </environments>

        <!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到 mybatis-config.xml中-->

        <mappers>

            <mapper resource="EmployeeMapper.xml"/>

        </mappers>

    </configuration>

package com.test.mybatis.dao;

import com.test.mybatis.Employee;

public interface EmployeeMapper {

    public Employee getEmpAndDept(Integer id);

}

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper

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

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

    <mapper namespace="com.test.mybatis.dao.EmployeeMapper">

    <!-- 
　　　　　方法一：

        联合查询：级联属性封装结果集

     -->

    <resultMap type="com.test.mybatis.Employee" id="MyEmp">

        <!--

            指定主键列的封装规则

            id定义主键会底层优化

            column：指定哪一列

            property：指定对应的JavaBean

         -->

        <id column="id" property="id"/>

        <!-- 普通列封装 -->

        <result column="last_name" property="lastName"/>

        <result column="email" property="email"/>

        <result column="gender" property="gender"/>

        <result column="did" property="depart.id"/>

        <result column="dept_name" property="depart.departName"/>

    </resultMap>

    <!-- 
　　　　方法二：

        使用association定义单个对象的封装规则

     -->

    <resultMap type="com.test.mybatis.Employee" id="MyEmp2">

        <id column="id" property="id"/>

        <result column="last_name" property="lastName"/>

        <result column="email" property="email"/>

        <result column="gender" property="gender"/>

        <!--

        association可以指定联合的Javabean对象

        property:指定那个属性是联合的对象

        JavaType：指定这个属性对象的类型（不能省略）

         -->

        <association property="depart" javaType="com.test.mybatis.Depart">

            <id column="did" property="id"/>

            <id column="dept_name" property="departName"/>

        </association>

    </resultMap>

     <!--

         查询Employee的同时查询员工对应的部门

      -->

      <select id="getEmpAndDept" resultMap="MyEmp2">

            SELECT e.id id,e.last_name last_name,e.email email,e.gender gender,d.id did,d.dept_name dept_name

            from

            tbl_depat d,tbl_employee  e

            where d.id=e.d_id AND e.id=#{id}

      </select>

    </mapper>

package com.test.mybatis.test;

import java.io.IOException;

import java.io.InputStream;

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.test.mybatis.Employee;

import com.test.mybatis.dao.EmployeeMapper;

public class MyBatisTest {

    //读取配置文件，得到SQLSessionFactory

    public SqlSessionFactory getSqlSessionFactory() throws IOException{

        String resource="mybatis-config.xml";

        InputStream is=Resources.getResourceAsStream(resource);

        return new SqlSessionFactoryBuilder().build(is);

    }

    @Test

    public void test01() throws IOException{

        //获取sqlSessionFactory对象

        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

        //获取sqlSession

        //代表和数据库的一次对话，用完必须关闭，相当于connection，都是非线程安全。每次使用都应该获取新的对象

        SqlSession openSession = sqlSessionFactory.openSession();

        try{

        //获取接口的实现类对象

        //会为接口自动的创建一个代理对象，代理对象去执行增删查改方法

        //mapper接口没有实现类，但是mybatis会为这个接口生成一个代理对象

        //（将接口和xml进行绑定）

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

        Employee emp = mapper.getEmpAndDept(6);

        System.out.println(emp+":"+emp.getDepart());

        }finally{

            openSession.close();

        }

    }

}