Hibernate入门04_双向多对一

这里还是以顾客和订单之间的关系来说明，一个客户可以有多个订单，但是一个订单只能对应一个客户；

1、项目的目录结构

2、Customer.java

import java.util.HashSet;
import java.util.Set;
/**客户-可以有多个 */
public class Customer {
    private Integer customerId;
    private String customerName;
    /**需要把集合初始化防止发生null指针异常*/
    private Set<Order> orders = new HashSet<>();
    //get/set...
}

Customer.hbm.xml映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-3-25 18:05:11 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping package="com.hibernate.entities.n21both">
    <class name="Customer" table="CUSTOMERS">
        <id name="customerId" type="java.lang.Integer">
            <column name="CUSTOMER_ID" />
            <generator class="native" />
        </id>
        <property name="customerName" type="java.lang.String">
            <column name="CUSTOMER_NAME" />
        </property>
        <!-- 映射一对多的集合映射 set的三个属性： inverse="true":放弃维护关联关系，让Order来维护， cascade="delete":设置级联关系删除 
            ， cascade="delete-orphan"；开发是不建议设置cascade，建议手动删除 order-by:在查询时对集合中的元素进行排序 -->
        <set name="orders" table="ORDERS" inverse="true" order-by="ORDER_NAME DESC">
            <key column="CUSTOMER_ID"></key>
            <one-to-many class="Order" />
        </set>
    </class>
</hibernate-mapping>

3、Order.java

public class Order {
    private Integer orderId;
    private String orderName;
    private Customer customer;
    //set/get...
}

Order.hbm.xml映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-3-25 18:05:11 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping package="com.hibernate.entities.n21both">
    <class name="Order" table="ORDERS">
        <id name="orderId" type="java.lang.Integer">
            <column name="ORDERID" />
            <generator class="native" />
        </id>
        <property name="orderName" type="java.lang.String">
            <column name="ORDER_NAME" />
        </property>
        <!-- 映射多对一的关联关系  使用多对一的关联关系 -->
        <many-to-one name="customer" class="Customer" column="CUSTOMER_ID"></many-to-one>
    </class>
</hibernate-mapping>

4、hibernate.cfg.xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>

    <!-- 配置链接数据库的基本信息 -->
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate01</property>

        <!-- hibernate的基本信息 -->
        <!-- hibernate使用的数据库方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
        <!-- 执行操作时是否在控制台打印sql语句 -->
        <property name="show_sql">true</property>
        <!-- 是否对sql进行格式化 -->
        <property name="format_sql">true</property>
        <!-- 指定自动生成数据表的策略 -->
        <property name="hbm2ddl.auto">update</property>
        <!-- 设置hibernate的隔离级别 -->
        <property name="connection.isolation">2</property>
        <!-- 删除对象后，设置其OID为null -->
        <property name="use_identifier_rollback">true</property>

        <!-- 配置C3P0数据源 -->
        <property name="c3p0.max_size">100</property>
        <property name="c3p0.min_size">5</property>
        <property name="c3p0.acquire_increment">2</property>
        <property name="c3p0.idle_test_period">2000</property>
        <property name="c3p0.timeout">2000</property>
        <property name="c3p0.max_statements">10</property>

        <!-- 设置JDBC的statement读取数据库的时候每次从数据库中读取记录条数，这个值100合适，太大会损耗内存，小了速度慢 -->
        <property name="jdbc.fetch_size">100</property>
        <!-- 设置数据库进行批量删除，更新，插入的时候批次的大小，30比较合适 -->
        <property name="jdbc.batch_size">30</property>



        <!-- 指定关联的hbm.xml文件 -->
        <mapping resource="com/hibernate/entities/n21both/Order.hbm.xml"/>
        <mapping resource="com/hibernate/entities/n21both/Customer.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

5、Test测试

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.hibernate.entities.n21both.Customer;
import com.hibernate.entities.n21both.Order;

public class HibernateTest {

    private SessionFactory sessionFactory;
    private Session session;
    private Transaction transaction;

    @Test
    public void testOne2ManySave() {
        Customer customer = new Customer();
        customer.setCustomerName("AA");

        Order order1 = new Order();
        order1.setOrderName("Oyder1");

        Order order2 = new Order();
        order2.setOrderName("Oyder2");
        // 设定关联关系
        order1.setCustomer(customer);
        order2.setCustomer(customer);
        customer.getOrders().add(order1);
        customer.getOrders().add(order2);

        // 三条insert两条update
        session.save(customer);
        session.save(order1);
        session.save(order2);

        // 三条insert，4条update
        // session.save(order1);
        // session.save(order2);
        // session.save(customer);

    }

    @Test
    public void testOne2ManyGet() {
        // 对多的一端采用延迟加载
        Customer customer = (Customer) session.get(Customer.class, 1);
        System.out.println(customer.getCustomerName());
        System.out.println(customer.getOrders().getClass());
    }

    @Test
    public void testOne2ManyDelete(){
        //设定级联 cascade="delete":设置级联关系删除关系后，可以删除
        Customer customer = (Customer) session.get(Customer.class, 1);
        session.delete(customer);
    }
    @Test
    public void testCascade_Orphan(){
        //设定级联 cascade="delete-orphan":设置级联关系删除关系后，可以删除
        Customer customer = (Customer) session.get(Customer.class, 2);
        customer.getOrders().clear();
//      session.delete(customer);

    }

    @Before
    public void init() {
        System.out.println("HibernateTest.init()");

        // 1.创建一个sessionFactory对象
        Configuration configuration = new Configuration().configure();
        ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties())
                .buildServiceRegistry();
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);

        // 2.创建一个session对象
        session = sessionFactory.openSession();

        // 3.开启事务
        transaction = session.beginTransaction();

    }

    @After
    public void destroy() {
        System.out.println("HibernateTest.destroy()");
        // 5.提交事务
        transaction.commit();
        // 6.关闭session
        session.close();
        // 7.关闭SessionFactory
        sessionFactory.close();

    }

}

6、备注：本博客适合有一定java基础，对数据库有一定认识的读者。不会做过多的文字描述，敬请原谅。本人也是新手，写博客当做笔记作分享，不喜勿喷，欢迎指教。