MyBatis高级映射查询(3)

一、数据库数据和项目搭建过程

1、主要要四张表，分别为user用户信息表、items商品表、orderdetail订单明细表、orders订单表。表的结构和数据如下：

表结构

CREATE DATABASE mybatis DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci
CREATE TABLE `items` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(32) NOT NULL COMMENT '商品名称',
  `price` FLOAT(10,1) NOT NULL COMMENT '商品定价',
  `detail` TEXT COMMENT '商品描述',
  `pic` VARCHAR(64) DEFAULT NULL COMMENT '商品图片',
  `createtime` DATETIME NOT NULL COMMENT '生产日期',
  PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

CREATE TABLE `orderdetail` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `orders_id` INT(11) NOT NULL COMMENT '订单id',
  `items_id` INT(11) NOT NULL COMMENT '商品id',
  `items_num` INT(11) DEFAULT NULL COMMENT '商品购买数量',
  PRIMARY KEY (`id`),
  KEY `FK_orderdetail_1` (`orders_id`),
  KEY `FK_orderdetail_2` (`items_id`),
  CONSTRAINT `FK_orderdetail_1` FOREIGN KEY (`orders_id`) REFERENCES `orders` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `FK_orderdetail_2` FOREIGN KEY (`items_id`) REFERENCES `items` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=INNODB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

CREATE TABLE `orders` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `user_id` INT(11) NOT NULL COMMENT '下单用户id',
  `number` VARCHAR(32) NOT NULL COMMENT '订单号',
  `createtime` DATETIME NOT NULL COMMENT '创建订单时间',
  `note` VARCHAR(100) DEFAULT NULL COMMENT '备注',
  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;

CREATE TABLE `user` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `username` VARCHAR(32) NOT NULL COMMENT '用户名称',
  `birthday` DATE DEFAULT NULL COMMENT '生日',
  `sex` CHAR(1) DEFAULT NULL COMMENT '性别',
  `address` VARCHAR(256) DEFAULT NULL COMMENT '地址',
  PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8;

表数据

INSERT  INTO `items`(`id`,`name`,`price`,`detail`,`pic`,`createtime`) VALUES (1,'台式机',3000.0,'该电脑质量非常好！！！！',NULL,'2015-02-03 13:22:53'),(2,'笔记本',6000.0,'笔记本性能好，质量好！！！！！',NULL,'2015-02-09 13:22:57'),(3,'背包',200.0,'名牌背包，容量大质量好！！！！',NULL,'2015-02-06 13:23:02');

INSERT  INTO `orderdetail`(`id`,`orders_id`,`items_id`,`items_num`) VALUES (1,3,1,1),(2,3,2,3),(3,4,3,4),(4,4,2,3);

INSERT  INTO `orders`(`id`,`user_id`,`number`,`createtime`,`note`) VALUES (3,1,'1000010','2015-02-04 13:22:35',NULL),(4,1,'1000011','2015-02-03 13:22:41',NULL),(5,10,'1000012','2015-02-12 16:13:23',NULL);

INSERT  INTO `user`(`id`,`username`,`birthday`,`sex`,`address`) VALUES (1,'王五',NULL,'2',NULL),(10,'张三','2014-07-10','1','北京市'),(16,'张小明',NULL,'1','河南郑州'),(22,'陈小明',NULL,'1','河南郑州'),(24,'张三丰',NULL,'1','河南郑州'),(25,'陈小明',NULL,'1','河南郑州'),(26,'王五',NULL,NULL,NULL);

2、整个项目的目录结构

3、首先创建mybatis配置文件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>
 <!-- 加载属性文件 -->
     <properties resource="db.properties">

     </properties>

     <!-- 和spring整合后 environments配置将废除-->
     <environments default="development">
         <environment id="development">
         <!-- 使用jdbc事务管理，事务控制由mybatis-->
             <transactionManager type="JDBC" />
         <!-- 数据库连接池，由mybatis管理-->
             <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>
         <mapper resource="sqlmap/Orders.xml" />
     </mappers>
 </configuration>

4、创建数据库配置文件db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123

5、创建映射文件orders.xml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">

 <mapper namespace="com.zhang.dao.OrdersDao">

     <select id="findOrdersUser"  resultType="com.zhang.domain.OrdersCustom">
         SELECT orders.*, USER.username,USER.sex,USER.address FROM orders,USER WHERE
         orders.user_id = user.id
     </select>

       <resultMap type="com.zhang.domain.Orders" id="OrdersUserResultMap">
         <id column="id" property="id"/>
         <result column="user_id" property="userId"/>
         <result column="number" property="number"/>
         <result column="createtime" property="createtime"/>
         <result column="note" property="note"/>

         <association property="user"  javaType="com.zhang.domain.User">
             <id column="user_id" property="id"/>
             <result column="username" property="username"/>
             <result column="sex" property="sex"/>
             <result column="address" property="address"/>
         </association>
     </resultMap>
     <select id="findOrdersUserResultMap" resultMap="OrdersUserResultMap">
         SELECT orders.*, USER.username,USER.sex,USER.address FROM orders,USER WHERE
         orders.user_id = user.id
     </select>

     <resultMap type="com.zhang.domain.Orders" id="OrdersAndOrderDetailResultMap" extends="OrdersUserResultMap" >

          <collection property="orderdetails" ofType="com.zhang.domain.Orderdetail">
              <id column="orderdetail_id" property="id"/>
              <result column="items_id" property="itemsId"/>
              <result column="items_num" property="itemsNum"/>
              <result column="orders_id" property="ordersId"/>
          </collection>
     </resultMap>

     <!-- 查询订单关联查询用户及订单明细，使用resultmap -->
     <select id="findOrdersAndOrderDetailResultMap" resultMap="OrdersAndOrderDetailResultMap">
         SELECT
           orders.*,
           USER.username,
           USER.sex,
           USER.address,
           orderdetail.id orderdetail_id,
           orderdetail.items_id,
           orderdetail.items_num,
           orderdetail.orders_id
         FROM
           orders,
           USER,
           orderdetail
         WHERE orders.user_id = user.id AND orderdetail.orders_id=orders.id
     </select>

     <!-- 查询用户及购买的商品 -->
     <resultMap type="com.zhang.domain.User" id="UserAndItemsResultMap">
         <!-- 用户信息 -->
         <id column="user_id" property="id"/>
         <result column="username" property="username"/>
         <result column="sex" property="sex"/>
         <result column="address" property="address"/>
         <!-- 订单信息一个用户对应多个订单，使用collection映射-->
          <collection property="ordersList" ofType="com.zhang.domain.Orders">
              <id column="id" property="id"/>
              <result column="user_id" property="userId"/>
             <result column="number" property="number"/>
             <result column="createtime" property="createtime"/>
             <result column="note" property="note"/>
              <!-- 订单明细 一个订单包括 多个明细-->
               <collection property="orderdetails" ofType="com.zhang.domain.Orderdetail">
                       <id column="orderdetail_id" property="id"/>
                      <result column="items_id" property="itemsId"/>
                      <result column="items_num" property="itemsNum"/>
                      <result column="orders_id" property="ordersId"/>
                      <!-- 商品信息一个订单明细对应一个商品-->
                    <association property="items" javaType="com.zhang.domain.Items">
                        <id column="items_id" property="id"/>
                        <result column="items_name" property="name"/>
                        <result column="items_detail" property="detail"/>
                        <result column="items_price" property="price"/>
                    </association>
               </collection>
          </collection>
     </resultMap>

     <!-- 查询用户及购买的商品信息，使用resultmap -->
     <select id="findUserAndItemsResultMap" resultMap="UserAndItemsResultMap">
         SELECT
           orders.*,
           USER.username,
           USER.sex,
           USER.address,
           orderdetail.id orderdetail_id,
           orderdetail.items_id,
           orderdetail.items_num,
           orderdetail.orders_id,
           items.name items_name,
           items.detail items_detail,
           items.price items_price
         FROM
           orders,
           USER,
           orderdetail,
           items
         WHERE orders.user_id = user.id AND orderdetail.orders_id=orders.id AND orderdetail.items_id = items.id
     </select>
 </mapper>

6、创建接口类OrderDao.java

 package com.zhang.dao;

 import java.util.List;

 import com.zhang.domain.Orders;
 import com.zhang.domain.OrdersCustom;
 import com.zhang.domain.User;
 public interface OrdersDao {

         //查询订单关联查询用户信息
         public List<OrdersCustom> findOrdersUser()throws Exception;

         //查询订单关联查询用户使用resultMap
         public List<Orders> findOrdersUserResultMap()throws Exception;

         //查询订单(关联用户)及订单明细
         public List<Orders>  findOrdersAndOrderDetailResultMap()throws Exception;

         //查询用户购买商品信息
         public List<User>  findUserAndItemsResultMap()throws Exception;

         //查询订单关联查询用户，用户信息是延迟加载
         public List<Orders> findOrdersUserLazyLoading()throws Exception;
 }

7、创建各种实体类user、orders、items、ordersdetail类

user类

 package com.zhang.domain;

 import java.io.Serializable;
 import java.util.Date;
 import java.util.List;

 public class User implements Serializable {

     //属性名和数据库表的字段对应
     private int id;
     private String username;// 用户姓名
     private String sex;// 性别
     private Date birthday;// 生日
     private String address;// 地址

     //用户创建的订单列表
     private List<Orders> ordersList;

     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 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;
     }
     public String getAddress() {
         return address;
     }
     public void setAddress(String address) {
         this.address = address;
     }
     @Override
     public String toString() {
         return "User [id=" + id + ", username=" + username + ", sex=" + sex
                 + ", birthday=" + birthday + ", address=" + address + "]";
     }
     public List<Orders> getOrdersList() {
         return ordersList;
     }
     public void setOrdersList(List<Orders> ordersList) {
         this.ordersList = ordersList;
     }

 }

orders类

 package com.zhang.domain;

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

 public class Orders {
     private Integer id;

     private Integer userId;

     private String number;

     private Date createtime;

     private String note;

     //用户信息
     private User user;

     //订单明细
     private List<Orderdetail> orderdetails;

     public Integer getId() {
         return id;
     }

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

     public Integer getUserId() {
         return userId;
     }

     public void setUserId(Integer userId) {
         this.userId = userId;
     }

     public String getNumber() {
         return number;
     }

     public void setNumber(String number) {
         this.number = number == null ? null : number.trim();
     }

     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 == null ? null : note.trim();
     }

     public User getUser() {
         return user;
     }

     public void setUser(User user) {
         this.user = user;
     }

     public List<Orderdetail> getOrderdetails() {
         return orderdetails;
     }

     public void setOrderdetails(List<Orderdetail> orderdetails) {
         this.orderdetails = orderdetails;
     }

 }

l

items类

 package com.zhang.domain;

 import java.util.Date;

 public class Items {
     private Integer id;

     private String name;

     private Float price;

     private String pic;

     private Date createtime;

     private String detail;

     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 == null ? null : name.trim();
     }

     public Float getPrice() {
         return price;
     }

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

     public String getPic() {
         return pic;
     }

     public void setPic(String pic) {
         this.pic = pic == null ? null : pic.trim();
     }

     public Date getCreatetime() {
         return createtime;
     }

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

     public String getDetail() {
         return detail;
     }

     public void setDetail(String detail) {
         this.detail = detail == null ? null : detail.trim();
     }

     @Override
     public String toString() {
         return "Items [id=" + id + ", name=" + name + ", price=" + price
                 + ", pic=" + pic + ", createtime=" + createtime + ", detail="
                 + detail + "]";
     }

 }

orderdetail类

 package com.zhang.domain;

 public class Orderdetail {
     private Integer id;

     private Integer ordersId;

     private Integer itemsId;

     private Integer itemsNum;

     //明细对应的商品信息
     private Items items;

     public Integer getId() {
         return id;
     }

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

     public Integer getOrdersId() {
         return ordersId;
     }

     public void setOrdersId(Integer ordersId) {
         this.ordersId = ordersId;
     }

     public Integer getItemsId() {
         return itemsId;
     }

     public void setItemsId(Integer itemsId) {
         this.itemsId = itemsId;
     }

     public Integer getItemsNum() {
         return itemsNum;
     }

     public void setItemsNum(Integer itemsNum) {
         this.itemsNum = itemsNum;
     }

     public Items getItems() {
         return items;
     }

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

     @Override
     public String toString() {
         return "Orderdetail [id=" + id + ", ordersId=" + ordersId
                 + ", itemsId=" + itemsId + ", itemsNum=" + itemsNum + "]";
     }

 }

8、创建测试类TestMy.java

 package com.zhang.test;

 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;

 import com.zhang.dao.OrdersDao;
 import com.zhang.domain.Orders;
 import com.zhang.domain.OrdersCustom;
 import com.zhang.domain.User;

 public class TestMy {
     private SqlSessionFactory sqlSessionFactory;

     // 此方法是在执行testFindUserById之前执行
     @Before
     public void setUp() throws Exception {
         // 创建sqlSessionFactory
         // mybatis配置文件
         String resource = "SqlMapConfig.xml";
         // 得到配置文件流
         InputStream inputStream = Resources.getResourceAsStream(resource);
         // 创建会话工厂，传入mybatis的配置文件信息
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
     }

     //一对一查询利用resultType
     @Test
     public void findOrdersUser() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersDao ordersDao = sqlSession.getMapper(OrdersDao.class);
         List<OrdersCustom> list=ordersDao.findOrdersUser();
         System.out.println(list.size());
     }

     //一对一查询利用resultMap
     @Test
     public void findOrdersUserResultMap() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersDao ordersDao = sqlSession.getMapper(OrdersDao.class);
         List<Orders> list=ordersDao.findOrdersUserResultMap();
         System.out.println(list.size());
     }

     //一对多查询
     @Test
     public void findOrdersAndOrderDetailResultMap() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersDao ordersDao = sqlSession.getMapper(OrdersDao.class);
         List<Orders> list=ordersDao.findOrdersAndOrderDetailResultMap();
         System.out.println(list.size());
     }

     //多对多查询
     @Test
     public void findUserAndItemsResultMap() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersDao ordersDao = sqlSession.getMapper(OrdersDao.class);
         List<User> list=ordersDao.findUserAndItemsResultMap();
         System.out.println(list.size());
     }

 }

二、一对一高级查询

1.需求:查询订单信息，关联查询创建订单的用户信息

2. 利用 resultType映射查询，创建pojo类继承Orders类

 package com.zhang.domain;

 //通过此类映射订单和用户查询的结果，让此类继承包括 字段较多的pojo类
 public class OrdersCustom extends Orders{

     //添加用户属性
     private String username;
     private String sex;
     private String address;

     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;
     }
     public String getAddress() {
         return address;
     }
     public void setAddress(String address) {
         this.address = address;
     }

 }

3、编写findOrdersUser接口

4、在Orders.xml文件定义SQL映射关系

5、测试方法：

6、利用resultMap映射查询，在Orders类中添加User属性：

7、编写接口方法

8、在Orders.xml中添加ResultMap信息：

9、测试方法：

三、一对多查询

1.需求：查询订单及订单明细的信息。

2.在Orders类中新增属性。

3、编写接口方法

4、在order.xml编写resultMap，继承上面的resultMap

5、测试方法

四、多对多查询

1.需求:查询用户及用户购买商品信息。

2.实现思路：

将用户信息映射到user中。

在user类中添加订单列表属性List<Orders> orderslist，将用户创建的订单映射到orderslist

3、在Orders中添加订单明细列表属性List<OrderDetail>orderdetials，将订单的明细映射到orderdetials

4、在OrderDetail中添加Items属性，将订单明细所对应的商品映射到Items

5、编写接口方法

6、测试方法

五、知识点总结

1、resultMap与resultType：

resultType： 将查询结果按照sql列名pojo属性名一致性映射到pojo中。

场合：常见一些明细记录的展示，比如用户购买商品明细，将关联查询信息全部展示在页面时，此时可直接使用resultType将每一条记录映射到pojo中，在前端页面遍历list（list中是pojo）即可。

resultMap：使用association和collection完成一对一和一对多高级映射（对结果有特殊的映射要求）。

2、association

作用： 将关联查询信息映射到一个pojo对象中。（一个对象）

场合：为了方便查询关联信息可以使用association将关联订单信息映射为用户对象的pojo属性中，比如：查询订单及关联用户信息。使用resultType无法将查询结果映射到pojo对象的pojo属性中，根据对结果集查询遍历的需要选择使用resultType还是resultMap。     

3、collection

作用：将关联查询信息映射到一个list集合中。

场合：为了方便查询遍历关联信息可以使用collection将关联信息映射到list集合中，比如：查询用户权限范围模块及模块下的菜单，可使用collection将模块映射到模块list中，将菜单列表映射到模块对象的菜单list属性中，这样的作的目的也是方便对查询结果集进行遍历查询。

资源下载链接：http://download.csdn.net/detail/u013865056/9907226