Mybatis使用resultType实现一对一查询

Posted 2020-06-18 小玄影123

引入mybatis相关jar，本示例是基于3.2.7版本，引入相关数据库驱动jar

创建两张数据库表

user表

CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) NOT NULL COMMENT ‘用户姓名‘,
  `birthday` date DEFAULT NULL COMMENT ‘出生日期‘,
  `sex` char(1) DEFAULT NULL COMMENT ‘性别‘,
  `address` varchar(256) DEFAULT NULL COMMENT ‘住址‘,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8

orders表

CREATE TABLE `orders` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL COMMENT ‘下单用户id号‘,
  `number` varchar(32) NOT NULL COMMENT ‘用户订单号‘,
  `createtime` datetime NOT NULL COMMENT ‘创建订单的时间‘,
  `note` varchar(100) DEFAULT NULL COMMENT ‘备注信息‘,
  PRIMARY KEY (`id`),
  KEY `FK_orders_1` (`user_id`),
  CONSTRAINT `FK_orders_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8

创建user的javabean对象

import java.util.Date;

public class User {
    private int id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    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 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 + "]";
    }

}

创建user的扩展类匹配输出结果

import cn.zqq.bean.User;

public class UserCustom extends User{
    private String number;
    private Date craetetime;
    private String note;
    public String getNumber() {
        return number;
    }
    public void setNumber(String number) {
        this.number = number;
    }
    public Date getCraetetime() {
        return craetetime;
    }
    public void setCraetetime(Date craetetime) {
        this.craetetime = craetetime;
    }
    public String getNote() {
        return note;
    }
    public void setNote(String note) {
        this.note = note;
    }
    
    @Override
    public String toString() {
        return "UserCustom [number=" + number + ", craetetime=" + craetetime + ", note=" + note +"id=" + super.getId() + ", username=" + super.getUsername() + ", birthday=" + super.getBirthday() + ", sex=" + super.getSex() + ", address="
                + super.getAddress() + "]";
    }
}

编写SqlMapConfig.xml使其在classpath中，数据库相关配置以mysql为例

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="****" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
     　　//基于包的扫描对相应的mapper.xml的读取
        <package name="对应的包名"/>
    </mappers>
</configuration>

编写UserCustomOrder.xml（mapper.xml的实际名字可任意）

<?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">
//namespace的名字和对应的接口全类名相同
<mapper namespace="cn.zqq.one2one.UserCustomOrder">
    <select id="findAllInfoUserOrders" resultType="包名.UserCustom">
        SELECT * FROM USER,orders WHERE user.id=orders.user_id;
    </select>    
</mapper>

编写对应的UserCustomOrder.java类名和mapper.xml的具体名字对应，

import java.util.List;

public interface UserCustomOrder {
    public List<UserCustom> findAllInfoUserOrders()throws Exception;
}

编写测试类

import java.io.IOException;
import java.io.InputStream;
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;
public class TestOne2One {
    
    SqlSession sqlSession = null;
    
    @Before
    public void beforesourse() throws IOException{
　　　　//加载配置文件
        String resource = "SqlMapConfig.xml";
　　　　//获取相关文件的流
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //得到sqlSession工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder()
                .build(inputStream);
　　　　//得到sqlSession
        sqlSession = sqlSessionFactory.openSession();
    }
   
    @Test
    public void findAllInfoUserOrders() throws Exception {
　　　　
　　　　//使用mapper代理获得实例结果
        UserCustomOrder order = sqlSession.getMapper(UserCustomOrder.class);
        List<UserCustom> userOrders = order.findAllInfoUserOrders();
        for (UserCustom userCustom : userOrders) {
            System.out.println(userCustom);
        }
　　　　sqlSession.close();
　　} 
}

运行上边的程序便可得到结果，简单应用，正在学习中