Mybatis实现一对一

项目结构

在这里插入图片描述

配置文件

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.xiaoge</groupId>
    <artifactId>one2many</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

</project>

jdbcConfig.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/eesy_mybatis
jdbc.username=root
jdbc.password=123456

SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <!--配置properties-->
    <properties resource="jdbcConfig.properties">
    </properties>


    <!-- 使用typeAliases配置别名, 它只能配置domain中类的别名 -->
    <typeAliases>
        <package name="com.xiaoge.domain"></package>
    </typeAliases>

    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql环境-->
        <environment id="mysql">
            <!--配置事务-->
            <transactionManager type="JDBC"></transactionManager>

            <!--配置连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}" />
                <property name="url" value="${jdbc.url}" />
                <property name="username" value="${jdbc.username}" />
                <property name="password" value="${jdbc.password}" />
            </dataSource>

        </environment>
    </environments>

    <mappers>
        <package name="com.xiaoge.dao"></package>
    </mappers>
</configuration>

accountDao.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.xiaoge.dao.AccountDao">

    <!-- 定义封装account和user的resultMap -->
    <resultMap id="accountUserMap" type="account">
        <id property="id" column="id"></id>
        <result property="uid" column="uid"></result>
        <result property="money" column="money"></result>
        <!-- 一对一的关系映射, 配置封装user的内容 -->
        <!-- javaType是下面谢谢信息, 封装在哪个实体类中 -->
        <association property="user" column="uid" javaType="user">
            <id property="id" column="id"></id>
            <result property="username" column="username"></result>
            <result property="birthday" column="birthday"></result>
            <result property="sex" column="sex"></result>
            <result property="address" column="address"></result>
        </association>
    </resultMap>


    <!-- 查询所有 (这是使用了mybatis映射关系实现的一对一)(实际开发中通常使用这种) -->
    <select id="findAll" resultMap="accountUserMap">
        <!-- select * from account -->
        select user.username, user.address, account.* from account, user where user.id = account.uid
    </select>

  
    <!-- 查询所有账户同时包含用户名和地址 (这是用了新的实体类完成的一对一) -->
    <select id="findAllAccount" resultType="AccountUser">
        select user.username, user.address, account.* from account, user where user.id = account.uid
    </select>
</mapper>

实体类

User

package com.xiaoge.domain;

import java.util.Date;

/**
 * @Author: 潇哥
 * @DateTime: 2020/3/4 下午4:03
 * @Description: TODO
 */
public class User {

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    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 +
                '}';
    }
}

AccountUser

package com.xiaoge.domain;

/**
 * @Author: 潇哥
 * @DateTime: 2020/3/17 上午11:57
 * @Description: TODO
 */
public class AccountUser extends Account {

    private String username;
    private String address;

    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;
    }

    @Override
    public String toString() {
        return super.toString() + "        AccountUser{" +
                "username='" + username + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

Account

package com.xiaoge.domain;

/**
 * @Author: 潇哥
 * @DateTime: 2020/3/16 下午6:02
 * @Description: TODO
 */
public class Account {

    private Integer id;
    private Integer uid;
    private Double money;

    // 从表实体应该包含一个主表实体的对象引用
    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 getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", uid=" + uid +
                ", money=" + money +
                '}';
    }
}

持久层接口

AccountDao

package com.xiaoge.dao;

import com.xiaoge.domain.Account;
import com.xiaoge.domain.AccountUser;

import java.util.List;

/**
 * @Author: 潇哥
 * @DateTime: 2020/3/16 下午6:08
 * @Description: TODO
 */
public interface AccountDao {

    /**
     * 查询所有账户, 同时还要获取当前账户的所属用户信息
     * @return
     */
    public List<Account> findAll();


    /**
     * 查询所有账户, 并且带有用户名称和地址信息
     * @return
     */
    public List<AccountUser> findAllAccount();

}

测试持久层接口方法

AccountTest

package com.xiaoge.test;

import com.xiaoge.dao.AccountDao;
import com.xiaoge.domain.Account;
import com.xiaoge.domain.AccountUser;
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.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @Author: 潇哥
 * @DateTime: 2020/3/16 下午6:12
 * @Description: TODO
 */
public class AccountTest {

    private SqlSession session;
    private AccountDao accountDao;
    private InputStream is;

    @Before
    public void init() throws IOException {
        is = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(is);
        session = factory.openSession();
        accountDao = session.getMapper(AccountDao.class);
    }

    @After
    public void destroy() throws IOException {

        if (session != null) {
            session.commit();
            session.close();
        }

        if (is != null) {
            is.close();
        }

    }

    /**
     * 测试查询所有(这是使用了mybatis映射关系实现的)
     */
    @Test
    public void findAllTest(){
        List<Account> list = accountDao.findAll();

        for (Account account : list) {
            System.out.println("-----------每个account信息------------");
            System.out.println(account);
            System.out.println(account.getUser());
        }
      
      	// 运行结果
        -----------每个account信息------------
        Account{id=1, uid=41, money=1000.0}
        User{id=1, username='老王', address='北京', sex='null', birthday=null}
        -----------每个account信息------------
        Account{id=2, uid=42, money=1000.0}
        User{id=2, username='小二王', address='北京金燕龙', sex='null', birthday=null}
        -----------每个account信息------------
        Account{id=3, uid=43, money=2000.0}
        User{id=3, username='小二王', address='北京金燕龙', sex='null', birthday=null}
        -----------每个account信息------------
        Account{id=4, uid=43, money=3000.0}
        User{id=4, username='小二王', address='北京金燕龙', sex='null', birthday=null}
    }

    /**
     * 测试查询所有账户, 同时包含用户名称和地址 (这是使用了新的实体类完成的)
     */
    @Test
    public void findAllAccountUserTest(){
        List<AccountUser> list = accountDao.findAllAccount();

        for (AccountUser accountUser : list) {
            System.out.println(accountUser);
        }
      
      	// 运行结果
      	Account{id=1, uid=41, money=1000.0}        AccountUser{username='老王', address='北京'}
        Account{id=2, uid=42, money=1000.0}        AccountUser{username='小二王', address='北京金燕龙'}
        Account{id=3, uid=43, money=2000.0}        AccountUser{username='小二王', address='北京金燕龙'}
        Account{id=4, uid=43, money=3000.0}        AccountUser{username='小二王', address='北京金燕龙'}

    }

}

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Mybatis实现一对一

Mybatis实现一对一

项目结构

配置文件

实体类

持久层接口

测试持久层接口方法

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