框架--mybatis框架之表间的关联关系

最新推荐文章于 2023-08-26 18:31:57 发布

HUWD

最新推荐文章于 2023-08-26 18:31:57 发布

阅读量194

点赞数

CC 4.0 BY-SA版权

分类专栏：框架文章标签： java mybatis 关联表一对多一对一

本文链接：https://blog.youkuaiyun.com/weixin_45089791/article/details/98881724

框架专栏收录该内容

23 篇文章

订阅专栏

本文深入解析MyBatis框架中多表关联的实现，包括一对一、一对多及多对多关系，通过具体示例代码展示如何配置映射文件与实体类，实现数据库表间复杂关系的数据查询。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

mybatis框架之多表关联关系(基于xml文件)

表与表之间都有哪些关系？

一对一关系： 一个订单只能对应一个用户
一对多关系： 一个用户可以对应多个订单
多对多关系： 多个订单详情对应多个商品

一对一关系示例

这里演示两种方式实现一对一关系，使用resultType和使用resultMap的方式，代码中有注释讲解
表结构
- myuser表结构
- orders表结构

po层实体类代码

myuser表映射的实体类MyUser类：

import java.sql.Date;

/**
 * 这是数据库user表对应的java实体类
 * 属性值对应数据库表的每个字段
 *
 * 并生成它的set get方法和tostring方法
 */
public class MyUser {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;

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 "MyUser{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", birthday=" + birthday +
            ", sex='" + sex + '\'' +
            ", address='" + address + '\'' +
            '}';
    }
}

orders表映射的实体类Order类

import java.sql.Date;

/*
* 这是数据库商品表对应的java实体类
* 表中的字段映射java类中的属性名
* 并生成它的set get和tostring方法
* */
public class Order {
private Integer id;
private Integer user_id;
private String number;
private Date createtime;
private String note;

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getUser_id() {
    return user_id;
}

public void setUser_id(Integer user_id) {
    this.user_id = user_id;
}

public String getNumber() {
    return number;
}

public void setNumber(String number) {
    this.number = number;
}

public Date getCreatetime() {
    return createtime;
}

public void setCreatetime(Date createtime) {
    this.createtime = createtime;
}

public String getNote() {
    return note;
}

public void setNote(String note) {
    this.note = note;
}

@Override
public String toString() {
    return "Order{" +
            "id=" + id +
            ", user_id=" + user_id +
            ", number='" + number + '\'' +
            ", createtime=" + createtime +
            ", note='" + note + '\'' +
            '}';
    }
}

Order类的一个扩展类，这个类是使用resultMap的方式实现一对一关系时使用。

/*
* 这是order类的扩展类，继承order类
* 在order的基础上增加username address属性
*在映射文件中使用resultMap的方式时，使用
* */
public class OrderCustom extends Order {
private String username;
private String address;
//这个是使用resultmap 将数据先映射到一个map中
private MyUser myUser;

public MyUser getMyUser() {
    return myUser;
}

public void setMyUser(MyUser myUser) {
    this.myUser = myUser;
}

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;
    }
}

配置你的全局核心配置文件，注意更改你的数据源的，数据库，用户名，密码。

<?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="dev">
    <environment id="dev">
<!--            设置事务类型-->
        <transactionManager type="JDBC"></transactionManager>
<!--            设置数据源类型-->
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver"/>
            <property name="url" value="jdbc:mysql://localhost:3306/你的库"/>
            <property name="username" value="用户名"/>
            <property name="password" value="密码"/>
        </dataSource>
    </environment>
</environments>
<!--    注入你的映射文件-->
<mappers>
    <mapper resource="ordertouserMapper.xml"></mapper>
</mappers>
</configuration>

配置一对一的映射文件，注意映射文件编写好要在全局配置文件中添加。

<?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">
<!--    注意这里的namespace的路径，如果使用getmap的话就要写映射接口的路径-->
<mapper namespace="com.wdhcr.onetoone.mapper">
    <!--    第一种方式：这是多表查询的多表之间一对一的关系-->
    <select id="orderToUserOneToOne" resultType="com.wdhcr.onetomany.po.OrderCustom">
        select orders.*,myuser.username,myuser.address from orders,myuser where orders.user_id 	= myuser.id
</select>
<!--    第二种方式：依旧是一对一关系。但是使用resultmap的方式，映射到一个resultmap中-->
<!--    创建一个resultmap 这里是映射到到order的一个扩展类上，这个扩展类中添加myuser属性-->
<resultMap id="oneToOneResultMap" type="com.wdhcr.onetoone.po.OrderCustom">
    <!--    当字段是主键时使用id标签column字段名映射property是实体类中的属性名-->
    <id column="id" property="id"></id>
    <result column="user_id" property="user_id"></result>
    <result column="number" property="number"></result>
    <result column="createtime" property="createtime"></result>
    <result column="note" property="note"></result>
    <!--添加实体类中的其他类对象的属性-->
    <association property="myUser" javaType="com.wdhcr.onetoone.po.MyUser">
        <result column="id" property="id"></result>
        <result column="username" property="username"></result>
        <result column="birthday" property="birthday"></result>
        <result column="sex" property="sex"></result>
        <result column="address" property="address"></result>
    </association>
</resultMap>
<!--一对一关系的验证，使用resultmap的方式-->
<select id="onetooneResultMap" resultMap="oneToOneResultMap">
    select orders.*,myuser.username,myuser.address from orders,myuser where orders.user_id = myuser.id
</select>
</mapper>

接下来就是测试类代码：

import com.wdhcr.onetoone.po.OrderCustom;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class Test {
public static void main(String[] args) throws IOException {
    //注意此处的路径
    //加载 mybatis 配置文件
    InputStream resourceAsStream = Resources.getResourceAsStream("ConfigMapper.xml");
    //构建sqlSession的工厂
    SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
    //根据 sqlSessionFactory 产生 session
    SqlSession sqlSession = build.openSession();
    //第一种方式：使用resultype的方式验证数据库表之间一对一关系
//        List<OrderCustom> orderCustoms = 		sqlSession.selectList("com.wdhcr.onetoone.mapper.orderToUserOneToOne");
//        for (OrderCustom orderCustom : orderCustoms) {
//            System.out.println(orderCustom);
//        }
    //第二种方式使用resulmap的方式验证数据库表之间一对一关系
    List<OrderCustom> orderCustoms= sqlSession.selectList("com.wdhcr.onetoone.mapper.onetooneResultMap");
    for (OrderCustom orderCustom : orderCustoms) {
        System.out.println(orderCustom);
        }
    }
}

以上就实现多表之间一对一关系（一个订单对应一个用户）

一对多的关系

使用resultMap的方式
表结构
- myuser表结构
- orders表结构
- orderdetail表结构

po层实体类代码

myuser表映射的实体类MyUser类：

import java.sql.Date;

/**
 * 这是数据库user表对应的java实体类
 * 属性值对应数据库表的每个字段
 *
 * 并生成它的set get方法和tostring方法
 */
public class MyUser {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;

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 "MyUser{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", birthday=" + birthday +
            ", sex='" + sex + '\'' +
            ", address='" + address + '\'' +
            '}';
    }
}

orders表映射的实体类Order类

import java.sql.Date;

/*
* 这是数据库商品表对应的java实体类
* 表中的字段映射java类中的属性名
* 并生成它的set get和tostring方法
* */
public class Order {
private Integer id;
private Integer user_id;
private String number;
private Date createtime;
private String note;

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getUser_id() {
    return user_id;
}

public void setUser_id(Integer user_id) {
    this.user_id = user_id;
}

public String getNumber() {
    return number;
}

public void setNumber(String number) {
    this.number = number;
}

public Date getCreatetime() {
    return createtime;
}

public void setCreatetime(Date createtime) {
    this.createtime = createtime;
}

public String getNote() {
    return note;
}

public void setNote(String note) {
    this.note = note;
}

@Override
public String toString() {
    return "Order{" +
            "id=" + id +
            ", user_id=" + user_id +
            ", number='" + number + '\'' +
            ", createtime=" + createtime +
            ", note='" + note + '\'' +
            '}';
    }
}

orderdetail表映射的实体类OrderDetail类

/*
* 这是映射订单表中的字段对应的实体类
* 有对应数据库表中字段的属性
* 并生成get set方法和tostring方法
* */
public class OrderDetail {
private Integer id;
private Integer orders_id;
private  Integer items_id;
private Integer items_num;

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getOrders_id() {
    return orders_id;
}

public void setOrders_id(Integer orders_id) {
    this.orders_id = orders_id;
}

public Integer getItems_id() {
    return items_id;
}

@Override
public String toString() {
    return "OrderDetail{" +
            "id=" + id +
            ", orders_id=" + orders_id +
            ", items_id=" + items_id +
            ", items_num=" + items_num +
            '}';
}

public void setItems_id(Integer items_id) {
    this.items_id = items_id;
}

public Integer getItems_num() {
    return items_num;
}

public void setItems_num(Integer items_num) {
    this.items_num = items_num;
    }
}

order类的一个扩展类

/*
* 这是order类的扩展类，继承order类
* 在order的基础上增加username address属性
*
* */
public class OrderCustom extends Order {
private String username;
private String address;
//这个是使用resultmap 将数据先映射到一个map中
private MyUser myUser;
//验证一对多的关系，一个订单对应多个明细
private OrderDetail orderDetail;

public OrderDetail getOrderDetail() {
    return orderDetail;
}

public void setOrderDetail(OrderDetail orderDetail) {
    this.orderDetail = orderDetail;
}

public MyUser getMyUser() {
    return myUser;
}

public void setMyUser(MyUser myUser) {
    this.myUser = myUser;
}

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;
   }
}

配置你的全局核心配置文件，注意更改你的数据源的，数据库，用户名，密码。

<?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="dev">
    <environment id="dev">
<!--            设置事务类型-->
        <transactionManager type="JDBC"></transactionManager>
<!--            设置数据源类型-->
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver"/>
            <property name="url" value="jdbc:mysql://localhost:3306/test"/>
            <property name="username" value="root"/>
            <property name="password" value="123456"/>
        </dataSource>
    </environment>
</environments>
<!--    注入你的映射文件-->
<mappers>
    <!--添加一对多的映射文件-->
    <mapper resource="oneTomany.xml"></mapper>
</mappers>
</configuration>

配置一对多的映射文件，注意映射文件编写好要在全局配置文件中添加。

<?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">
<!--    注意这里的namespace的路径，如果使用getmap的话就要写映射接口的路径-->
<mapper namespace="com.wdhcr.onetomany.mapper">
<!--    创建一个resultmap 这里是映射到到order的一个扩展类上，这个扩展类中添加myuser属性-->
<resultMap id="oneToOneResultMap" type="com.wdhcr.onetomany.po.OrderCustom">
    <!--    当字段是主键时使用id标签column字段名映射property是实体类中的属性名-->
    <id column="id" property="id"></id>
    <result column="user_id" property="user_id"></result>
    <result column="number" property="number"></result>
    <result column="createtime" property="createtime"></result>
    <result column="note" property="note"></result>
    <!--添加实体类中的其他类对象的属性-->
    <association property="myUser" javaType="com.wdhcr.onetomany.po.MyUser">
        <result column="id" property="id"></result>
        <result column="username" property="username"></result>
        <result column="birthday" property="birthday"></result>
        <result column="sex" property="sex"></result>
        <result column="address" property="address"></result>
    </association>
</resultMap>
<!--使用resultmap验证一对多的关系，使这个resultmap继承上面的resultmap，
使其可使用上面resultmap中的属性，并添加自己的属性-->
<resultMap id="onTomany" type="com.wdhcr.onetomany.po.OrderCustom" extends="oneToOneResultMap">
    <association property="orderDetail" javaType="com.wdhcr.onetomany.po.OrderDetail">
        <result column="id" property="id"></result>
        <result column="orders_id" property="orders_id"></result>
        <result column="items_id" property="items_id"></result>
        <result column="items_num" property="items_num"></result>
    </association>
</resultMap>
<!--验证多表之间一对多的关系-->
<select id="oneToManySelect" resultMap="onTomany">
    SELECT myuser.`username`,myuser.`birthday`,myuser.`address`,orders.`createtime`,
orders.`number`,orders.`note` FROM myuser,orders,orderdetail WHERE
myuser.`id`=orders.`user_id` AND orders.id=orderdetail.`orders_id`
    </select>
</mapper>

测试类代码：

import com.wdhcr.onetomany.po.OrderCustom;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class Test {
public static void main(String[] args) throws IOException {
    InputStream resourceAsStream = Resources.getResourceAsStream("ConfigMapper.xml");
    SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = build.openSession();
    List<OrderCustom> orderCustoms=sqlSession.selectList("com.wdhcr.onetomany.mapper.oneToManySelect");
    for (OrderCustom orderCustom : orderCustoms) {
        //因为有tostring方法，所以直接打印对象即可
        System.out.println(orderCustom);
     }
    }
}

多对多关系

表结构
- myuser表结构
- orders表结构
- orderdetail表结构
- items表结构

orders表映射的实体类Order类,注意是实现多对多的关系，一个用户可以有多个订单，所以添加了一个 List myOrderslist属性

import java.util.Date;
import java.util.List;
/**
 * 这是数据库user表对应的java实体类
 * 属性值对应数据库表的每个字段
 *
 * 并生成它的set get方法和tostring方法
 * 由于要实现多对多的关系，所以在user类中添加订单属性，还是多个订单
 */
public class Myuser {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
//用户下面有你的 定单的列表---一个用户下面可以有很多的订单
private List<Orders> myOrderslist;

public List<Orders> getMyOrderslist() {
    return myOrderslist;
}

public void setMyOrderslist(List<Orders> myOrderslist) {
    this.myOrderslist = myOrderslist;
}

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 "Myuser{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", birthday=" + birthday +
            ", sex='" + sex + '\'' +
            ", address='" + address + '\'' +
            ", myOrderslist=" + myOrderslist +
            '}';
    }


}

orders表映射的实体类Order类

import java.sql.Date;
import java.util.List;

/*
 * 这是数据库商品表对应的java实体类
 * 表中的字段映射java类中的属性名
 * 并生成它的set get和tostring方法
 * 一个订单下可以有多个订单明细，所以添加
 * List<OrderDetail> getOrderDetailslist()属性
 * */
public class Orders {


private Integer id;
private Integer user_id;
private Integer number;
private Date createtime;
private Myuser myuser;

public Myuser getMyuser() {
    return myuser;
}

public void setMyuser(Myuser myuser) {
    this.myuser = myuser;
}

// 一个订单下面可以有很的多的订单明细

public List<OrderDetail> getOrderDetailslist() {
    return orderDetailslist;
}

public void setOrderDetailslist(List<OrderDetail> orderDetailslist) {
    this.orderDetailslist = orderDetailslist;
}

private List<OrderDetail> orderDetailslist;

public Date getCreatetime() {
    return createtime;
}

public void setCreatetime(Date createtime) {
    this.createtime = createtime;
}

private String note;

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getUser_id() {
    return user_id;
}

public void setUser_id(Integer user_id) {
    this.user_id = user_id;
}

public Integer getNumber() {
    return number;
}

public void setNumber(Integer number) {
    this.number = number;
}

public String getNote() {
    return note;
}

public void setNote(String note) {
    this.note = note;
}


@Override
public String toString() {
    return "Orders{" +
            "id=" + id +
            ", user_id=" + user_id +
            ", number=" + number +
            ", createtime=" + createtime +
            ", note='" + note + '\'' +
            ", myuser=" + myuser +
            ", orderDetailslist=" + orderDetailslist +
            '}';
    }
}

orderdetail表映射的实体类OrderDetail类

/*
 * 这是映射订单表中的字段对应的实体类
 * 有对应数据库表中字段的属性
 * 并生成get set方法和tostring方法
 * */
public class OrderDetail {


private Integer id;
private Integer order_id;
private Integer items_id;
private Integer items_num;
//这个就是在你的商品明细中有一个商品
//从用户----订单---订单明细---商品
private Items items;

public Items getItems() {
    return items;
}

public void setItems(Items items) {
    this.items = items;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public Integer getOrder_id() {
    return order_id;
}

public void setOrder_id(Integer order_id) {
    this.order_id = order_id;
}

public Integer getItems_id() {
    return items_id;
}

public void setItems_id(Integer items_id) {
    this.items_id = items_id;
}

public Integer getItems_num() {
    return items_num;
}

public void setItems_num(Integer items_num) {
    this.items_num = items_num;
}


@Override
public String toString() {
    return "OrderDetail{" +
            "id=" + id +
            ", order_id=" + order_id +
            ", items_id=" + items_id +
            ", items_num=" + items_num +
            ", items=" + items +
            '}';
    }
}

items表映射的实体类Item类

import java.util.Arrays;
import java.util.Date;

/**
 * 这是数据库items表对应的java实体类
 * 属性值对应数据库表的每个字段
 * <p>
 * 并生成它的set get方法和tostring方法
 */
public class Items {
@Override
public String toString() {
    return "Items [id=" + id + ", name=" + name + ", price=" + price + ", detail=" + detail + ", pic="
            + Arrays.toString(pic) + ", createtime=" + createtime + "]";
}

private Integer id;
private String name;
private Double price;
private String detail;
private byte[] pic;
private Date createtime;

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Double getPrice() {
    return price;
}

public void setPrice(Double price) {
    this.price = price;
}

public String getDetail() {
    return detail;
}

public void setDetail(String detail) {
    this.detail = detail;
}

public byte[] getPic() {
    return pic;
}

public void setPic(byte[] pic) {
    this.pic = pic;
}

public Date getCreatetime() {
    return createtime;
}

public void setCreatetime(Date createtime) {
    this.createtime = createtime;
   }


}

全局核心配置文件，注意你的库，用户名，密码

<?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="dev">
    <environment id="dev">
<!--            设置事务类型-->
        <transactionManager type="JDBC"></transactionManager>
<!--            设置数据源类型-->
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver"/>
            <property name="url" value="jdbc:mysql://localhost:3306/库"/>
            <property name="username" value="用户名"/>
            <property name="password" value="密码"/>
        </dataSource>
    </environment>
</environments>
<!--    注入你的映射文件-->
<mappers>
   <!--添加多对多关系映射文件-->
    <mapper resource="manyToMany.xml"></mapper>
</mappers>
</configuration>

多对多关系映射文件

<?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">
<!--    注意这里的namespace的路径，如果使用getmap的话就要写映射接口的路径-->
<mapper namespace="com.wdhcr">
<resultMap type="com.wdhcr.manytomany.po.Myuser" id="userAndItemsResultMap">

    <!-- 用户信息 里面对应有订单信息-->
    <id column="id" property="id"/>
    <result column="username" property="username"/>
    <result column="sex" property="sex"/>
    <result column="address" property="address"/>

    <!-- 订单信息 里面对应有订单详细信息-->
    <collection property="myOrderslist" ofType="com.wdhcr.manytomany.po.Orders">
        <id column="id" property="id"/>
        <result column="user_id" property="user_id"/>
        <result column="number" property="number"/>
        <result column="createtime" property="createtime"/>
        <result column="note" property="note"/>


        <!-- 订单明细里面对应有商品信息 -->
        <collection property="orderDetailslist" ofType="com.wdhcr.manytomany.po.OrderDetail">
            <id column="id" property="id"/>
            <result column="orders_id" property="orders_id"/>
            <result column="items_id" property="items_id"/>
            <result column="items_num" property="items_num"/>

            <!-- 商品信息 -->
            <association property="items" javaType="com.wdhcr.manytomany.po.Items">
                <id column="id" property="id"/>
                <result column="name" property="name"/>
                <result column="price" property="price"/>
                <result column="createtime" property="createtime"/>
            </association>


        </collection>
    </collection>
</resultMap>
<select id="manytomany" resultMap="userAndItemsResultMap">
SELECT  myuser.*,orders.`number`,orders.`createtime`,orders.`note`,orderdetail.`items_id`,orderdetail.`items_num`,items.`nam	e`,items.`price` FROM myuser,orders,orderdetail,items WHERE
myuser.`id`=orders.`user_id` AND orderdetail.`orders_id`=orders.`id`AND orderdetail.`items_id`=items.`id`

</select>

</mapper>

测试类代码：

import com.wdhcr.manytomany.po.Myuser;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class Test {
public static void main(String[] args) throws IOException {
    InputStream resourceAsStream = Resources.getResourceAsStream("ConfigMapper.xml");
    SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = build.openSession();
    List<Myuser> myusers = sqlSession.selectList("com.wdhcr.manytomany");
    for (Myuser myuser : myusers) {
        System.out.println(myuser);
     }
   }
}