mybatis关系映射之一对多和多对一

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本实例使用顾客和订单的例子做说明: 一个顾客可以有多个订单, 一个订单只对应一个顾客

二. 例子:

1. 代码结构图:

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2. 建表语句:

CREATE DATABASE test;  USE test;CREATE TABLE person(  personId VARCHAR(36) PRIMARY KEY,  personName VARCHAR(64),  personAddress VARCHAR(128),  personTel VARCHAR(11));CREATE TABLE orders(  orderId VARCHAR(36) PRIMARY KEY,  orderNumber VARCHAR(20),  orderPrice INT,  pid VARCHAR(36));INSERT INTO person VALUES('001', 'Jack', 'Wuhan', '1234567');INSERT INTO orders VALUES('O_00001', '00001', 100, '001');INSERT INTO orders VALUES('O_00002', '00002', 200, '001');SELECT p.*, o.*FROM person p   JOIN orders o ON (p.personId=o.pid)WHERE p.personId = '001'

3. 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;@Overridepublic String toString() {return "{id: " + id + ", name: " + name + ", address: " + address + ", tel: " + tel + "}";}}

4. 订单实体:

/** * 订单实体 */public class Order {private String id;private String number;private int price;private Person person; @Overridepublic String toString() {return "{id: " + id + ", number: " + number + ", price: " + price + "}";}}

5. 一对多实体配置: Person.xml

<?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.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>

6. 多对一实体配置:

<?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.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>

7. 总配置: sqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><typeAliases><typeAlias type="com.zdp.domain.Person" alias="Person"/>          <typeAlias type="com.zdp.domain.Order" alias="Order"/>  </typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC" /><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver" /><property name="url" value="jdbc:mysql://localhost/test" /><property name="username" value="root" /><property name="password" value="root" /></dataSource></environment></environments><mappers><!-- 映射文件的位置 --><mapper resource="com/zdp/domain/Person.xml" /><mapper resource="com/zdp/domain/Order.xml" /></mappers></configuration>

8. 测试文件:

/** * 测试一对多和多对一 */public class MybatisTest {private SqlSessionFactory ssf; @Beforepublic void initSF() throws Exception {String resource = "sqlMapConfig.xml";InputStream inputStream = Resources.getResourceAsStream(resource);ssf = new SqlSessionFactoryBuilder().build(inputStream);}@Test//一对多关联查询public void selectPersonById()throws Exception{SqlSession session = ssf.openSession();Person person = session.selectOne("com.zdp.domain.Person.selectPersonById", "001");System.out.println(person.getOrders());}@Test//多对一关联查询public void selectOrderById()throws Exception{SqlSession session = ssf.openSession();Order order = session.selectOne("com.zdp.domain.Order.selectOrderById", "O_00001");System.out.println(order.getPerson().getName());}}

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