Mybatis_03_一对多

 

1.User.java

package com.cmdzz.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

/**
 * @author cmdzz
 * @date 2019/6/26 - 12:01
 */
public class User implements Serializable {

    /**
     * 属性要和表的列名一样
     */
    private Integer id;
    private String userName;
    private Date birthday;
    private String sex;
    private String address;

    //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 Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }


    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

 

2.IUserDao.java

package com.cmdzz.dao;

/**
 * @author cmdzz
 * @date 2019/6/26 - 12:07
 */

import com.cmdzz.domain.User;

import java.util.List;

/**
 * 用户的持久层接口
 */
public interface IUserDao {

    /**
     * 查询所有操作
     * @return
     */
   /*注解的方式 @Select("select * from user")*/
    List<User> findAll();



    /**
     * 根据id查询用户信息
     * @param userId
     * @return
     */
    User findById(Integer userId);


}

 

3.IUserDao.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.cmdzz.dao.IUserDao">

    <!--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
            ofType是只哪个类，此处用了包扫描 的别名
        -->
        <collection property="accounts" ofType="account">
            <id column="aid" property="id"></id>
            <result column="uid" property="uid"></result>
            <result column="money" property="money"></result>
        </collection>

    </resultMap>

    <!--配置查询所有
      id="findAll" 是UserDao方法名 要一致
  -->
   <!-- <select id="findAll" resultType="user">
        select * from user
    </select>-->

    <select id="findAll" resultMap="userAccountMap">
       SELECT * FROM USER u LEFT OUTER JOIN account a ON u.`id` =a.`UID`
    </select>



    <!-- 根据id查询用户 -->
    <select id="findById" parameterType="INT" resultType="user">
        select * from user where id = #{uid}
    </select>


</mapper>

 

3.数据库测试语句

 

 发现有名字重复，但是mybaits 会自动识别组合到一个user下。

 

4.测试类

UserTest.java

package com.cmdzz.test;

import com.cmdzz.dao.IAccountDao;
import com.cmdzz.dao.IUserDao;
import com.cmdzz.domain.Account;
import com.cmdzz.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;

/**
 * @author cmdzz
 * @date 2019/6/26 - 17:21
 */
public class UserTest {


    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before//用于在测试方法执行之前执行
    public void init()throws Exception{
        //1.读取配置文件，生成字节输入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.获取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.获取SqlSession对象
        sqlSession = factory.openSession();
        //4.获取dao的代理对象
        userDao = sqlSession.getMapper(IUserDao.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();
        //6.释放资源
        sqlSession.close();
        in.close();
    }

    /**
    * 测试查询所有
    */
    @Test
    public void testFindAll() {

        //5.执行查询所有方法
        List<User> users = userDao.findAll();
        for(User user:users){
            System.out.println("用户信息====================");
            System.out.println(user);
            System.out.println(user.getAccounts());
        }

    }




}

 

 5.执行结果