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 mapperPUBLIC "-//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 mapperPUBLIC "-//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：