【mybatis一对一查询】方法二：resultMap

Dear 丶 2024-03-31 09:40 72阅读 0赞

## 代码部分 ##

com.qingruan.bean目录下创建Account.java和User.java

1、Account.java

>     package com.qingruan.bean;
>     
>     public class Account {
>         private Integer aid;
>         private Integer uid;
>         private double money;
>     
>         //在account类假如user类对象作为account类的一个属性
>         private User user;
>     
>         @Override
>         public String toString() {
>             return "Account{" +
>                     "aid=" + aid +
>                     ", uid=" + uid +
>                     ", money=" + money +
>                     ", user=" + user +
>                     '}';
>         }
>     
>         public User getUser() {
>             return user;
>         }
>     
>         public void setUser(User user) {
>             this.user = user;
>         }
>     
>         public Integer getAid() {
>             return aid;
>         }
>     
>         public void setAid(Integer aid) {
>             this.aid = aid;
>         }
>     
>         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;
>         }
>     }
>     package com.qingruan.bean;
>     
>     public class Account {
>         private Integer aid;
>         private Integer uid;
>         private double money;
>     
>         //在account类假如user类对象作为account类的一个属性
>         private User user;
>     
>         @Override
>         public String toString() {
>             return "Account{" +
>                     "aid=" + aid +
>                     ", uid=" + uid +
>                     ", money=" + money +
>                     ", user=" + user +
>                     '}';
>         }
>     
>         public User getUser() {
>             return user;
>         }
>     
>         public void setUser(User user) {
>             this.user = user;
>         }
>     
>         public Integer getAid() {
>             return aid;
>         }
>     
>         public void setAid(Integer aid) {
>             this.aid = aid;
>         }
>     
>         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;
>         }
>     }

2、User.java

>     package com.qingruan.bean;
>     
>     public class User {
>         private Integer id;
>         private String username;
>         private String sex;
>     
>         @Override
>         public String toString() {
>             return "User{" +
>                     "id=" + id +
>                     ", username='" + username + '\'' +
>                     ", sex='" + sex + '\'' +
>                     '}';
>         }
>     
>         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 getSex() {
>             return sex;
>         }
>     
>         public void setSex(String sex) {
>             this.sex = sex;
>         }
>     }

3、IAccountDao.java

>     package com.qingruan.dao;
>     
>     import com.qingruan.bean.Account;
>     
>     import java.util.List;
>     
>     public interface IAccountDao {
>     
>         /**
>          * 方法二：查询所有账户，同时获得所属用户的信息
>          * @return
>          */
>         List<Account> findAllAccount();
>     }

4、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.qingruan.dao.IAccountDao">
        
        <resultMap id="accountMap" type="Account">
            <id column="aid" property="aid"></id>
            <result column="uid" property="uid"></result>
            <result column="money" property="money"></result>
            
            <association property="user" javaType="user">
                <id column="id" property="id"></id>
                <result column="username" property="username"></result>
                <result column="sex" property="sex"></result>
            </association>
        </resultMap>
    
    
        
        <select id="findAllAccount" resultMap="accountMap" >
             SELECT a.*,u.`username`,u.`sex` FROM t_account a,t_user u WHERE a.`uid`=u.`id`
        </select>
    
    </mapper>

5、mybatis-config.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>
>     
>     
>         <settings>
>             <setting name="logImpl" value="LOG4J"/>
>         </settings>
>     
>         
>         <typeAliases>
>             
>             
>             <package name="com.qingruan.bean"/>
>         </typeAliases>
>     
>         
>         <environments default="mysql">
>             <environment id="mysql">
>                 
>                 <transactionManager type="JDBC"/>
>                 <dataSource type="POOLED">
>                     <property name="driver" value="com.mysql.jdbc.Driver"/>
>                     
>                     <property name="url" value="jdbc:mysql://localhost:3306/mydata1?useUnicode=true&characterEncoding=UTF-8"/>
>                     <property name="username" value="root"/>
>                     <property name="password" value="1234"/>
>                 </dataSource>
>             </environment>
>         </environments>
>     
>     
>         <mappers>
>             <mapper resource="com/qingruan/dao/AccountDao.xml"></mapper>
>     
>         </mappers>
>     
>     </configuration>

6、MyBatisTest

>     package com.qingruan.test;
>     
>     import com.qingruan.bean.Account;
>     import com.qingruan.dao.IAccountDao;
>     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 MyBatisTest {
>         private InputStream is;
>         private SqlSessionFactoryBuilder builder;
>         private SqlSessionFactory sessionFactory;
>         private SqlSession session;
>         private IAccountDao dao;
>     
>         @Before //在测试方法执行之前执行
>         public void init() throws  Exception{
>             is=Resources.getResourceAsStream("mybatis-config.xml");
>             //创建sqlSessionFacotory的构建着对象
>             builder=new SqlSessionFactoryBuilder();
>             //通过构建着对象创建工厂对象
>             sessionFactory = builder.build(is);
>             //获得session对象
>             session = sessionFactory.openSession();
>             //使用session创建dao接口的代理对象
>             dao = session.getMapper(IAccountDao.class);
>         }
>     
>         @After  //在测试方法执行完成之后执行
>         public void destroy() throws  Exception{
>             //提交事务  增删改后一定要控制事物的提交
>             session.commit();
>             //方式资源
>             session.close();
>             is.close();
>         }
>     
>     
>         /**
>          * 查账户的同时，显示用户信息，包括姓名和性别
>          */
>         @Test
>         public void testFindAll(){
>             List<Account> list = dao.findAllAccount();
>             for (Account account : list) {
>                 System.out.println(account);
>             }
>         }
>     
>     }

## 运行结果 ##

![2fe1c6b2cc1b4536a078b83f5655d5f0.png][]

[2fe1c6b2cc1b4536a078b83f5655d5f0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/e0f7b359043a4fb1ad83c365646d6a64.png