Mybatis 关联映射

一对多关联映射

买家和订单的关系就是一对多的关系
我们首先来创建person类和order类

public class Person {

    private String id;
    private String name;
    private String address;
    private String tel;

    List<Order> orders;

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getAddress() {
        return address;
    }

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

    public String getTel() {
        return tel;
    }

    public void setTel(String tel) {
        this.tel = tel;
    }

    public List<Order> getOrders() {
        return orders;
    }

    public void setOrders(List<Order> orders) {
        this.orders = orders;
    }
}

public class Order {

    private String id;
    private String number;
    private int price;

    private Person p;

    public String getId() {
        return id;
    }

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

    public String getNumber() {
        return number;
    }

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

    public int getPrice() {
        return price;
    }

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

    public Person getP() {
        return p;
    }

    public void setP(Person p) {
        this.p = p;
    }
}

并且在数据库中创建对应的实体类表，如下：

并添加数据如下：

接下来我们来配置映射文件。
Person.xml配置文件

<?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.cc.mybatis.domain.Person">

    <resultMap type="Person" id="personMap">
        <id column="personId" property="id"/>
        <result column="personName" property="name"/>
        <result column="personAddress" property="address"/>
        <result column="personTel" property="tel"/>

        <!-- 一对多 -->
        <!-- property:指的是集合属性的值 ofType：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>

    <select id="selectPersonById" parameterType="string" resultMap="personMap">
        select p.*,o.* from person p,orders o where p.personId  = o.pid and p.personId = #{id}
    </select>


</mapper>

添加映射文件到mybatis的配置中：

测试方法和测试结果：

多对一的映射

配置Order.xml，进行多对一的映射

<?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.cc.mybatis.domain.Order">
    <resultMap type="Order" id="orderMap">
            <id column="orderId" property="id"/>
            <result column="orderNumber" property="number"/>
            <result column="orderPrice" property="price"/>

            <!-- 多对一的关系 -->
            <association property="p" 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="orderMap">
        select p.*,o.* from person p,orders o where p.personId  = o.pid and o.orderId = #{id}
    </select>

</mapper>

再配置中加入映射文件：

测试方法和执行结果：