mybatis关系映射之一对多和多对一

一. 简介:

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:



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;

@Override
public 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;

@Override
public 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 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>

6. 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>

7. 总配置: sqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//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;

@Before
public 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());
}
}