MyBatis高级映射（一对一查询）

package org.mybatis.demo.po;

import java.util.Date;

public class User {

//属性名和数据库表的字段对应
private int id;
private String username;// 用户姓名
private String sex;// 性别
private Date birthday;// 生日
private String address;// 地址

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", sex=" + sex
+ ", birthday=" + birthday + ", address=" + address + "]";
}

}

package org.mybatis.demo.po;

import java.util.Date;
import java.util.List;

public class Orders {

private Integer id;
private Integer userId;
private String number;
private Date createtime;
private String note;
//用户信息
private User user;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public Integer getUserId() {
return userId;
}

public void setUserId(Integer userId) {
this.userId = userId;
}

public String getNumber() {
return number;
}

public void setNumber(String number) {
this.number = number == null ? null : number.trim();
}

public Date getCreatetime() {
return createtime;
}

public void setCreatetime(Date createtime) {
this.createtime = createtime;
}

public String getNote() {
return note;
}

public void setNote(String note) {
this.note = note == null ? null : note.trim();
}

public User getUser() {
return user;
}

public void setUser(User user) {
this.user = user;
}

}

<?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="org.mybatis.demo.mapper.OrdersMapperCustom">

<!-- 查询订单关联查询用户信息，使用resultmap -->
<select id="findOrdersUserResultMap" resultMap="OrdersUserResultMap">
SELECT
orders.*,
USER.username,
USER.sex,
USER.address
FROM
orders,
USER
WHERE orders.user_id = user.id
</select>

<!-- 订单查询关联用户的resultMap
将整个查询的结果映射到cn.itcast.mybatis.po.Orders中
-->
<resultMap type="org.mybatis.demo.po.Orders" id="OrdersUserResultMap">
<!-- 配置映射的订单信息 -->
<!-- id：指定查询列中的唯 一标识，订单信息的中的唯 一标识，如果有多个列组成唯一标识，配置多个id
column：订单信息的唯 一标识 列
property：订单信息的唯 一标识 列所映射到Orders中哪个属性
-->
<id column="id" property="id"/>
<result column="user_id" property="userId"/>
<result column="number" property="number"/>
<result column="createtime" property="createtime"/>
<result column="note" property="note"/>

<!-- 配置映射的关联的用户信息 -->
<!-- association：用于映射关联查询单个对象的信息
property：要将关联查询的用户信息映射到Orders中哪个属性
-->
<association property="user"  javaType="org.mybatis.demo.po.User">
<!-- id：关联查询用户的唯 一标识
column：指定唯 一标识用户信息的列
javaType：映射到user的哪个属性
-->
<id column="user_id" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>

</association>
</resultMap>

</mapper>

package org.mybatis.demo.mapper;

import java.util.List;

import org.mybatis.demo.po.Orders;

public interface OrdersMapperCustom {

public List<Orders> findOrdersUserResultMap();
}

package org.mybatis.demo.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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.Before;
import org.junit.Test;
import org.mybatis.demo.mapper.OrdersMapperCustom;
import org.mybatis.demo.po.Orders;
import org.mybatis.demo.po.OrdersCustom;

public class TestMyBatis {

private SqlSessionFactory sessionFactory;

@Before
public void createSqlSessionFactory() throws IOException {
//引入配置文件
String resource = "SqlMapConfig.xml";
InputStream ins = Resources.getResourceAsStream(resource);

//创建SqlSession对象
sessionFactory = new SqlSessionFactoryBuilder().build(ins);
}

@Test
public void test1() {
SqlSession session = null;
try {
session = sessionFactory.openSession();
OrdersMapperCustom mapper = session.getMapper(OrdersMapperCustom.class);
List<Orders> list = mapper.findOrdersUserResultMap();
for(Orders order : list){
System.out.println(order.getUser().getUsername());
}
} finally {
if(session != null){
session.close();
}
}
}

}