User类:
package com.qublog.domain;
import java.io.Serializable;
import java.util.Date;
import java.util.List;
public class User implements Serializable {
private Integer id;
private String username;
private String address;
private String sex;
private Date birthday;
//一对多关系映射,主表实体应该包含从表实体的集合引用
private List<Account> accounts;
public List<Account> getAccounts() {
return accounts;
}
public void setAccounts(List<Account> accounts) {
this.accounts = accounts;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
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;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", address='" + address + '\'' +
", sex='" + sex + '\'' +
", birthday=" + birthday +
'}';
}
}
UserDao类:
package com.qublog.dao;
import com.qublog.domain.User;
import java.util.List;
//用户的持久层接口
public interface UserDao {
//查询所有用户,同时获取到用户下所有账户的信息
List<User> findAll();
}
UserDao.xml
<?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="com.qublog.dao.UserDao">
<!-- 定义user的resultMap -->
<resultMap id="userAccountMap" type="user">
<id property="id" column="id"></id>
<result property="username" column="username"></result>
<result property="address" column="address"></result>
<result property="sex" column="sex"></result>
<result property="birthday" column="birthday"></result>
<!-- 配置user对象中accounts集合的映射 -->
<collection property="accounts" ofType="account">
<id property="id" column="aid"></id>
<result property="uid" column="uid"></result>
<result property="money" column="money"></result>
</collection>
</resultMap>
<!-- 配置查询所有 -->
<select id="findAll" resultMap="userAccountMap">
select u.*, a.id as aid, a.uid, a.money from user u left outer join account a on a.uid=u.id;
</select>
</mapper>
UserTest类:
package com.qublog.test;
import com.qublog.dao.AccountDao;
import com.qublog.dao.UserDao;
import com.qublog.domain.Account;
import com.qublog.domain.AccountUser;
import com.qublog.domain.User;
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.After;
import org.junit.Before;
import org.junit.Test;
import java.io.InputStream;
import java.util.List;
public class UserTest {
private InputStream in = null;
private SqlSession sqlSession = null;
UserDao userDao = null;
@Before //用于在测试方法执行之前执行
public void init() throws Exception {
//读取配置文件,生成字节输入流
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//获取SqlSessionFactory对象
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
//获取SqlSession对象
sqlSession = factory.openSession();
//获取dao代理对象
userDao = sqlSession.getMapper(UserDao.class);
}
@After //用于在测试方法执行之后执行
public void destroy() throws Exception {
//提交事务
sqlSession.commit();
//释放资源
sqlSession.close();
in.close();
}
@Test
public void testFindAll() throws Exception {
//执行查询所有方法
List<User> users = userDao.findAll();
for (User user:users) {
System.out.println(user);
System.out.println(user.getAccounts() );
}
}
}
结果:
从结果中可以看出mybatis自动将重复项合并了。