1、一对一：自动映射
Orders：
package com.jadan.pojo;
import java.util.Date;
public class Orders {
private Integer id;
private Integer userId;
private String number;
private Date createtime;
private String note;
public User getUser() {
return user;
}
public void setUser(User user) {
this.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();
}
}CustomerOrders：
package com.jadan.pojo;
import java.util.Date;
public class CustomerOrders extends Orders {
private int uid;
private String username;// 用户姓名
private String sex;// 性别
private Date birthday;// 生日
private String address;// 地址
public int getUid() {
return uid;
}
public void setUid(int uid) {
this.uid = uid;
}
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;
}
}
UserMapper.xml 映射文件：
<?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接口代理实现编写规则:
1. 映射文件中namespace要等于接口的全路径
2. 映射文件中sql语句id要等于接口的方法名
3. 映射文件中传入参数类型要等于接口方法的传入参数类型
4. 映射文件中返回结果集类型要等于接口方法的返回值类型
-->
<mapper namespace="com.jadan.mapper.UserMapper">
<!-- 一对一: 自动映射 -->
<select id="findOrdersAndUser1" resultType="com.jadan.pojo.CustomerOrders">
select o.*, u.id uid, username, birthday, sex, address
from orders o, user u
where o.user_id = u.id
</select>
</mapper>UserMapper.java 接口文件：
package com.jadan.mapper;
import java.util.List;
import com.jadan.pojo.CustomerOrders;
public interface UserMapper {
// 一对一: 自动映射
public List<CustomerOrders> findOrdersAndUser1();
}UserMapperTest.java 测试文件：
package mybatis_day01;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Date;
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 com.jadan.pojo.CustomerOrders;
import com.jadan.pojo.QueryVo;
public class UserMapperTest {
private SqlSessionFactory factory;
// 作用: 在测试方法前执行这个初始化方法
@Before
public void setUp() throws Exception {
// 核心配置文件名
String resource = "SqlMapConfig.xml";
// 通过流将核心配置文件读取进来
InputStream inputStream = Resources.getResourceAsStream(resource);
// 通过核心配置文件输入流来创建会话工厂
factory = new SqlSessionFactoryBuilder().build(inputStream);
}
// 一对一: 自动映射
@Test
public void testFindOrdersAndUser1() {
SqlSession openSession = factory.openSession();
// 通过getMapper方法来实例化接口
UserMapper mapper = openSession.getMapper(UserMapper.class);
List<CustomerOrders> list = mapper.findOrdersAndUser1();
System.out.println(list);
}
}2、一对一：手动映射
Orders：（与上面的Orders多了一个user属性）
package com.jadan.pojo;
import java.util.Date;
public class Orders {
private Integer id;
private Integer userId;
private String number;
private Date createtime;
private String note;
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.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();
}
}UserMapper.xml 映射文件：
<?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接口代理实现编写规则:
1. 映射文件中namespace要等于接口的全路径
2. 映射文件中sql语句id要等于接口的方法名
3. 映射文件中传入参数类型要等于接口方法的传入参数类型
4. 映射文件中返回结果集类型要等于接口方法的返回值类型
-->
<mapper namespace="com.jadan.mapper.UserMapper">
<!-- 一对一: 手动映射 -->
<!--
id: resultMap的唯一标识
type: 将查询出的数据放入这个指定的对象中
注意: 手动映射需要指定数据库中表的字段名与pojo类中属性名称对应关系
-->
<resultMap type="com.jadan.pojo.Orders" id="ordersAndUserResultMap">
<!-- id标签指定主键字段对应关系
column: 列,数据库中的字段名称
property: 属性,pojo中的属性名称
-->
<id column="id" property="id"/>
<!-- result: 标签指定非主键字段的对应关系 -->
<result column="user_id" property="userId"/>
<result column="number" property="number"/>
<result column="createtime" property="createtime"/>
<result column="note" property="note"/>
<!-- 这个标签指定单个对象的对应关系
property: 指定将数据放入Orders的user属性中
javaType: user属性的类型
-->
<association property="user" javaType="com.jadan.pojo.User">
<id column="uid" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="birthday" property="birthday"/>
<result column="address" property="address"/>
</association>
</resultMap>
<select id="findOrdersAndUser2" resultMap="ordersAndUserResultMap">
select o.*, u.id uid, username, birthday, sex, address
from orders o, user u
where o.user_id = u.id
</select>
</mapper>UserMapper.java 接口文件：
package com.jadan.mapper;
import java.util.List;
import com.jadan.pojo.Orders;
public interface UserMapper {
// 一对一: 手动映射
public List<Orders> findOrdersAndUser2();
}UserMapperTest 测试文件：
package mybatis_day01;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Date;
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 com.jadan.mapper.UserMapper;
import com.jadan.pojo.Orders;
public class UserMapperTest {
private SqlSessionFactory factory;
// 作用: 在测试方法前执行这个初始化方法
@Before
public void setUp() throws Exception {
// 核心配置文件名
String resource = "SqlMapConfig.xml";
// 通过流将核心配置文件读取进来
InputStream inputStream = Resources.getResourceAsStream(resource);
// 通过核心配置文件输入流来创建会话工厂
factory = new SqlSessionFactoryBuilder().build(inputStream);
}
// 一对一: 手动映射
@Test
public void testFindOrdersAndUser2() {
SqlSession openSession = factory.openSession();
// 通过getMapper方法实例化接口
UserMapper mapper = openSession.getMapper(UserMapper.class);
List<Orders> list = mapper.findOrdersAndUser2();
System.out.println(list);
}
}