mybatis连接数据库实现双表查询
作者：『 初橙ζ 』
本文主要介绍了mybatis连接数据库实现双表查询,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧
创建maven工程包
再点击下一步
自己定义项目名称，在下一步
设置自己本地仓库位置
最后点击完成。
建好后在pom.xml文件中添加mybatis以及相关架包
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mybatis </groupId>
<artifactId> mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.24</version>
</dependency>
</dependencies>这些架包可以从Maven Repository: Search/Browse/Explore (mvnrepository.com)获取.
接着连接数据库表的接口
import java.util.List;
public interface OrdersDAO {
public List<Orders> findOrderByUserid(long userid);
public void batchInsertOrder(List<Orders> ord);
}
public interface UserinfosDAO {
public List<Userinfos>findTop10();
public List<Userinfos>findUser(Userinfos user);
}以及实用类
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.Date;
import java.util.List;
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Userinfos {
private long userid;
private String username;
private Date birthday;
private String pwd;
private List<Orders> ords;
}import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.Date;
import java.util.List;
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Userinfos {
private long userid;
private String username;
private Date birthday;
private String pwd;
private List<Orders> ords;
}以及配置文件order.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.kgc.mymb.dao.OrdersDAO">
<!-- resulMap-->
<!-- 动态sql-->
<select id="findOrderByUserid" parameterType="long" resultType="order">
select * from orders where userid=#{userid}
</select>
<insert id="batchInsertOrder">
insert into orders values
<foreach collection="list" item="order" separator=",">
(#{order.ordid},#{order.userid},#{order.shopid},#{order.buynum})
</foreach>
</insert>
</mapper>和userinfos.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.kgc.mymb.dao.UserinfosDAO">
<!-- 动态sql-->
<select id="findUser" parameterType="user" resultType="user">
select* from userinfos
<where>
<if test="username != null">
username=#{username}
</if>
<if test="birthday != null">
and date_format(birthday,'%Y-%m-%d')=date_format(#{birthday},'%Y-%m-%d')
</if>
</where>
</select>
<!-- resulMap 关联性查询-->
<resultMap id="user_order" type="user">
<!-- collection 一对多
property 查询出订单的结果放在哪个属性中
column 用什么列传递给订单做参数
select 订单查询方法
-->
<result column="userid" property="userid"></result>
<collection property="ords"
column="userid"
select="com.kgc.mymb.dao.OrdersDAO.findOrderByUserid">
</collection>
</resultMap>
<select id="findTop10" resultMap="user_order">
select * from userinfos limit 10
</select>
</mapper>数据库链接文件mybatis.cfg.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>
<!-- 给自己的实体类起别名-->
<typeAliases>
<typeAlias type="com.kgc.mymb.domain.Userinfos" alias="user"></typeAlias>
<typeAlias type="com.kgc.mymb.domain.Orders" alias="order"></typeAlias>
</typeAliases>
<!-- 连接数据库配置-->
<environments default="cm">
<environment id="cm">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://192.168.47.3:3306/mydemo"/>
<property name="username" value="root"/>
<property name="password" value="ok"/>
</dataSource>
</environment>
</environments>
<!-- 加载用户的sql xml 文件-->
<mappers>
<mapper resource="mapper/userinfos.xml"></mapper>
<mapper resource="mapper/orders.xml"></mapper>
</mappers>
</configuration>最后测试类
public class Demo {
public static void main(String[] args) throws IOException {
//读取配置文件
Reader reader = Resources.getResourceAsReader("mybatis.cfg.xml");
// 开启SqlSessionFactory工厂
SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(reader);
//将你的dao接口注入到会话工厂配置对象中
// factory.getConfiguration().addMapper(UserinfosDAO.class);
//开启SqlSession
SqlSession session =factory.openSession();
//获取接口对象
// UserinfosDAO udao= session.getMapper(UserinfosDAO.class);
// Calendar cal=Calendar.getInstance();
// cal.set(1995,3,22,0,0,0);
// Userinfos us = Userinfos.builder().username("dpjbms").birthday(cal.getTime()).build();
// System.out.println(udao.findUser(us));
UserinfosDAO udao= session.getMapper(UserinfosDAO.class);
System.out.println( udao.findTop10());
// OrdersDAO ordersDAO = session.getMapper(OrdersDAO.class);
// Orders ord1=Orders.builder().ordid(10).userid(1).shopid(100).buynum(5).build();
// Orders ord2=Orders.builder().ordid(11).userid(2).shopid(1).buynum(1).build();
// List<Orders> ords=new ArrayList<>();
// ords.add(ord1);
// ords.add(ord2);
// ordersDAO.batchInsertOrder(ords);
// session.commit();
// OrdersDAO ordersDAO= session.getMapper(OrdersDAO.class);
// System.out.println(ordersDAO.findOrderByUserid(1));
//关闭会话
session.close();
}
}结果如图所示
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