mybatis关系映射之一对多和多对一

1. 顾客实体:

/** 

 * 客户实体  

 */  

public class Person {  

  

    private String id;  

    private String name;  

    private String address;  

    private String tel;  

      

    private List<Order> orders;  

      

    @Override  

    public String toString() {  

        return "{id: " + id + ", name: " + name + ", address: " + address + ", tel: " + tel + "}";  

    }  
}  

2. 订单实体:

/** 

 * 订单实体 

 */  

public class Order {  

  

    private String id;  

    private String number;  

    private int price;  

      

    private Person person;   

      

    @Override  

    public String toString() {  

        return "{id: " + id + ", number: " + number + ", price: " + price + "}";  

    }  

  

}  

3 . 一对多实体配置: Person.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.zdp.domain.Person">  

  

    <resultMap type="Person" id="personBean">  

        <id column="personId" property="id"/>  

        <result column="personName" property="name"/>  

        <result column="personAddress" property="address"/>  

        <result column="personTel" property="tel"/>  

          

        <!-- 一对多的关系 -->  

        <!-- property: 指的是集合属性的值, ofType：指的是集合中元素的类型 -->  

        <collection property="orders" ofType="Order">  

            <id column="orderId" property="id"/>  

            <result column="orderNumber" property="number"/>  

            <result column="orderPrice" property="price"/>  

        </collection>  

    </resultMap>  

      

    <!-- 根据id查询Person, 关联将Orders查询出来 -->  

    <select id="selectPersonById" parameterType="string" resultMap="personBean">  

        select p.*, o.* from person p, orders o where p.personId  = o.pid and p.personId = #{id}  

    </select>  

      

</mapper> 

4. 多对一实体配置:

<?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.zdp.domain.Order">  

    <resultMap type="Order" id="orderBean">  

        <id column="orderId" property="id"/>  

        <result column="orderNumber" property="number"/>  

        <result column="orderPrice" property="price"/>  

          

        <!-- 多对一的关系 -->  

        <!-- property: 指的是属性的值, javaType：指的是属性的类型-->  

        <association property="person" javaType="Person">  

            <id column="personId" property="id"/>  

            <result column="personName" property="name"/>  

            <result column="personAddress" property="address"/>  

            <result column="personTel" property="tel"/>  

        </association>  

    </resultMap>  

      

    <!-- 根据id查询Order, 关联将Person查询出来 -->  

    <select id="selectOrderById" parameterType="string" resultMap="orderBean">  

        select p.*, o.* from person p, orders o where p.personId  = o.pid and o.orderId = #{id}  

    </select>  

      

</mapper>