Mybatis学习（5）高级映射

需求：

一、一对一查询

查询订单信息，关联查询创建订单的用户信息；

orders--->user：一个订单只由一个用户创建，一对一

orders表 和 user表：

1）使用resultType方法：

思路: 查询订单的同时，关联查询用户信息；创建Order的扩展类，包含订单信息、用户信息；

pojo -- Orders：

 package com.cy.po;

 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;

     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();
     }
 }

Orders

pojo-- User：

 package com.cy.po;

 import java.util.Date;

 public class User {
     //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
         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 + "]";
         }
 }

User

pojo -- Order扩展类 OrdersCustom：

 package com.cy.po;

 /**
  *
  * <p>Description: 订单的扩展类</p>
  */
 //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
     /*USER.username,
       USER.sex,
       USER.address */
     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;
     }

 }

OrdersCustom

Mapper.xml:

<mapper namespace="com.cy.mapper.OrdersMapperCustom">

    <!-- 查询订单关联查询用户信息 -->
    <select id="findOrdersUser" resultType="com.cy.po.OrdersCustom">
        SELECT orders.*,USER.username,USER.sex,USER.address
        FROM orders,USER
        WHERE orders.user_id = user.id
    </select>

</mapper>

Mapper接口：

/**
 *
 * <p>Title: OrdersMapperCustom</p>
 * <p>Description: 订单mapper</p>
 */
public interface OrdersMapperCustom {

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

}

测试代码：

 public class OrdersMapperCustomTest {
     private SqlSessionFactory sqlSessionFactory;

     @Before
     public void setUp() throws Exception {
         String resource = "SqlMapConfig.xml";
         InputStream inputStream = Resources.getResourceAsStream(resource);
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
     }

     @Test
     public void testFindOrdersUser() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersMapperCustom ordersMapperCustom = sqlSession.getMapper(OrdersMapperCustom.class);
         List<OrdersCustom> list = ordersMapperCustom.findOrdersUser();
         System.out.println(list.toString());
         sqlSession.close();
     }

 }

2）使用resultMap方法：

思路：使用resultMap将查询结果中的订单信息映射到Orders对象中，在orders类中添加User属性，将关联查询出来的用户信息映射到orders对象中的user属性中。

Orders中保存user：

 package com.cy.po;

 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;

     private User user;

     public User getUser() {
         return user;
     }

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

     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();
     }
 }

包含user的Orders

Mapper.xml:

<mapper namespace="com.cy.mapper.OrdersMapperCustom">
    <!-- 订单查询关联用户的resultMap 将整个查询的结果映射到com.cy.po.Orders中-->
    <resultMap id="OrdersUserResultMap" type="com.cy.po.Orders">
        <!-- 配置映射的订单信息 -->
        <!-- id：指定查询列中的唯 一标识，订单信息的中的唯 一标识，如果有多个列组成唯一标识，配置多个id
            column：订单信息的唯一标识列
            property：订单信息的唯一标识 列所映射到Orders中哪个属性
          -->
        <id column="id" property="id"></id>
        <result column="user_id" property="userId"></result>
        <result column="number" property="number"></result>
        <result column="createtime" property="createtime"></result>
        <result column="note" property="note"></result>
        <!-- 配置映射的关联的用户信息 -->
        <!-- association：用于映射关联查询单个对象的信息  property：要将关联查询的用户信息映射到Orders中哪个属性 -->
        <association property="user" javaType="com.cy.po.User">
            <!-- id：关联查询用户的唯 一标识
            column：指定唯一标识用户信息的列  property：映射到user的哪个属性 -->
            <id column="user_id" property="id"/>
            <result column="username" property="username"/>
            <result column="sex" property="sex"/>
            <result column="address" property="address"/>
        </association>
    </resultMap>

    <!-- 查询订单关联查询用户信息，使用resultmap -->
    <select id="findOrdersUserResultMap" resultMap="OrdersUserResultMap">
        SELECT
        orders.*,
        USER.username,
        USER.sex,
        USER.address
        FROM
        orders,
        USER
        WHERE orders.user_id = user.id
    </select>

</mapper>

mapper接口：

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

测试代码：

@Test
    public void testFindOrdersUserResultMap() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        OrdersMapperCustom ordersMapperCustom = sqlSession.getMapper(OrdersMapperCustom.class);

        List<Orders> orders = ordersMapperCustom.findOrdersUserResultMap();
        System.out.println(orders);
        sqlSession.close();
    }

使用resultType和resultMap实现一对一查询的总结：

resultType：使用resultType实现较为简单，如果pojo中没有包括查询出来的列名，需要增加列名对应的属性，即可完成映射。

resultMap：需要单独定义resultMap，如果对查询结果有特殊的要求，使用resultMap可以完成将关联查询映射pojo的属性中。

resultMap可以实现延迟加载，resultType无法实现延迟加载。

二、一对多查询

需求：查询订单及订单明细的信息。

在orders.java类中添加List<orderDetail> orderDetails属性：

 package com.cy.po;

 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;

     private List<Orderdetail> orderdetails;

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

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

     public User getUser() {
         return user;
     }

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

     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();
     }
 }

Orders中包含Orderdetail的集合属性

 package com.cy.po;

 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 + "]";
     }

 }

订单明细类Orderdetail

mapper.xml:

 <mapper namespace="com.cy.mapper.OrdersMapperCustom">
     <!-- 订单及订单明细的resultMap 使用extends继承，不用在中配置订单信息和用户信息的映射 -->
     <resultMap id="OrdersAndOrderDetailResultMap" type="com.cy.po.Orders" extends="OrdersUserResultMap" >
         <!-- 订单信息 --><!-- 用户信息 --><!-- 使用extends继承，不用在中配置订单信息和用户信息的映射 -->

         <!-- 订单明细信息 一个订单关联查询出了多条明细，要使用collection进行映射
         collection：对关联查询到多条记录映射到集合对象中
         property：将关联查询到多条记录映射到com.cy.po.Orders哪个属性
         ofType：指定映射到list集合属性中pojo的类型
          -->
         <collection property="orderdetails" ofType="com.cy.po.Orderdetail">
             <!-- id：订单明细唯一标识 property:要将订单明细的唯 一标识映射到com.cy.po.Orderdetail的哪个属性 -->
             <id column="orderdetail_id" property="id"></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>

 </mapper>

mapper接口：

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

测试代码：

 @Test
     public void FindOrdersAndOrderDetailResultMap() throws Exception {
         SqlSession sqlSession = sqlSessionFactory.openSession();
         OrdersMapperCustom ordersMapperCustom = sqlSession.getMapper(OrdersMapperCustom.class);

         List<Orders> orders = ordersMapperCustom.findOrdersAndOrderDetailResultMap();
         System.out.println(orders);
         sqlSession.close();
     }

三、多对多查询

需求：查询用户及用户购买商品信息

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

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

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

在上面代码基础上，User类中添加List<Orders> orderslist:

 package com.cy.po;

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

 public class User {
     //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

         private List<Orders> orderslist;

         public List<Orders> getOrderslist() {
             return orderslist;
         }
         public void setOrderslist(List<Orders> orderslist) {
             this.orderslist = 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 + "]";
         }
 }

User中保存List

mapper.xml:

<mapper namespace="com.cy.mapper.OrdersMapperCustom">
    <!-- 查询用户及购买的商品 -->
    <resultMap type="com.cy.po.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.cy.po.Orders">
            <id column="id" property="id"></id>
            <result column="user_id" property="userId"></result>
            <result column="number" property="number"></result>
            <result column="createtime" property="createtime"></result>
            <result column="note" property="note"></result>
            <!-- 订单明细 一个订单包括 多个明细-->
            <collection property="orderdetails" ofType="com.cy.po.Orderdetail">
                <id column="orderdetail_id" property="id"></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.cy.po.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>

上面，其实思路就是用户中保存List<Orders>,然后Order中有多个订单明细List<Orderdetail>;一个订单明细对应一个商品，private Item;

顺着写来来就是了，不难。

mapper接口：

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

测试代码：

@Test
    public void FindUserAndItemsResultMap() throws Exception {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        OrdersMapperCustom ordersMapperCustom = sqlSession.getMapper(OrdersMapperCustom.class);

        List<User> users = ordersMapperCustom.findUserAndItemsResultMap();
        System.out.println(users);
        sqlSession.close();
    }

多对多查询总结：

将查询用户购买的商品信息明细清单，（用户名、用户地址、购买商品名称、购买商品时间、购买商品数量）

针对上边的需求就使用resultType将查询到的记录映射到一个扩展的pojo中，很简单实现明细清单的功能。