User.java :
package com.jadan.pojo;
import java.util.Date;
import java.util.List;
public class User {
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
private List<Orders> ordersList;
public List<Orders> getOrdersList() {
return ordersList;
}
public void setOrdersList(List<Orders> ordersList) {
this.ordersList = ordersList;
}
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 + "]";
}
}
UserMapper.xml 映射文件:
记得在 SqlMapConfig.xml 核心配置文件中引入
<?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">
<!-- 对集合对象的映射 -->
<!--
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.User" id="UserAndOrdersResultMap">
<!-- 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="username" property="username"/>
<result column="birthday" property="birthday"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>
<!-- collection指定对应的集合对象关系映射
property: 将数据放入User对象的ordersList属性中
ofType: 指定ordersList属性的泛型类型
-->
<collection property="ordersList" ofType="com.jadan.pojo.Orders">
<id column="oid" property="id"/>
<result column="user_id" property="userId"/>
<result column="number" property="number"/>
<result column="createtime" property="createtime"/>
<result column="note" property="note"/>
</collection>
</resultMap>
<select id="findUserAndOrders" resultMap="UserAndOrdersResultMap">
select user.*,orders.id oid, orders.user_id, orders.number,orders.createtime,orders.note
from user, orders
where user.id = orders.user_id
</select>
</mapper>
UserMapper.java 接口文件:
package com.jadan.mapper;
import java.util.List;
import com.jadan.pojo.User;
public interface UserMapper {
// 一对多
public List<User> findUserAndOrders();
}
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.User;
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);
}
// 一对多
@Test
public void testFindUserAndOrders() {
SqlSession openSession = factory.openSession();
// 通过getMapper方法来实例化接口
UserMapper mapper = openSession.getMapper(UserMapper.class);
List<User> list = mapper.findUserAndOrders();
System.out.println(list);
}
}