Hibernate实战——复合主键的成员属性为关联实体

一 配置

     
           
           com.mysql.jdbc.Driver
           
           jdbc:mysql://localhost/hibernate
           
           root
           
           32147
           
           20
           
           1
           
           5000
           
           100
           3000
           2
           true
           
           org.hibernate.dialect.MySQL5InnoDBDialect
           true
           true
           
           update
           
           
           
           
     

二 PO

1 Product

package org.crazyit.app.domain;
import javax.persistence.*;

@Entity
@Table(name="product_inf")
public class Product
{
     // 定义标识属性
     @Id @Column(name="product_id")
     @GeneratedValue(strategy=GenerationType.IDENTITY)
     private Integer productId;
     private String name;
     // 无参数的构造器
     public Product(){}
     // 初始化全部属性的构造器
     public Product(String name)
     {
           this.name = name;
     }
     // productId的setter和getter方法
     public void setProductId(Integer productId)
     {
           this.productId = productId;
     }
     public Integer getProductId()
     {
           return this.productId;
     }
     // name的setter和getter方法
     public void setName(String name)
     {
           this.name = name;
     }
     public String getName()
     {
           return this.name;
     }
}

2 OrderItem

package org.crazyit.app.domain;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.*;

@Entity
@Table(name="order_inf")
public class Order
{
    // 定义标识属性
    @Id @Column(name="order_id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer orderId;
    private Date orderDate;
    // 关联的的订单项
    @OneToMany(targetEntity=OrderItem.class, mappedBy="order")
    private Set items
        = new HashSet<>();

    // 无参数的构造器
    public Order(){}

    // 初始化全部成员变量的构造器
    public Order(Date orderDate)
    {
        this.orderDate = orderDate;
    }

    // orderId的setter和getter方法
    public void setOrderId(Integer orderId)
    {
        this.orderId = orderId;
    }
    public Integer getOrderId()
    {
        return this.orderId;
    }

    // orderDate的setter和getter方法
    public void setOrderDate(Date orderDate)
    {
        this.orderDate = orderDate;
    }
    public Date getOrderDate()
    {
        return this.orderDate;
    }

    // items的setter和getter方法
    public void setItems(Set items)
    {
        this.items = items;
    }
    public Set getItems()
    {
        return this.items;
    }
}

3 Order

package org.crazyit.app.domain;
import javax.persistence.*;

@Entity
@Table(name="order_item_inf")
public class OrderItem
     implements java.io.Serializable
{
     // 下面3个属性将作为联合主键
     // 定义关联的Order实体
     @ManyToOne(targetEntity=Order.class)
     // 映射名为order_id的外键列，参照order_inf的order_id主键列
     @JoinColumn(name="order_id" ,  referencedColumnName="order_id")
     @Id
     private Order order;
     // 定义关联的Product实体
     @ManyToOne(targetEntity=Product.class)
     // 映射名为product_id的外键列，参照product_inf的product_id主键列
     @JoinColumn(name="product_id" ,  referencedColumnName="product_id")
     @Id
     private Product product;
     // 该订单项订购的产品数量
     @Id
     private int count;
     // 无参数的构造器
     public OrderItem(){ }
     // 初始化全部成员变量的构造器
     public OrderItem(Order order , Product product , int  count)
     {
           this.order = order;
           this.product = product;
           this.count = count;
     }
     // order的setter和getter方法
     public void setOrder(Order order)
     {
           this.order = order;
     }
     public Order getOrder()
     {
           return this.order;
     }
     // product的setter和getter方法
     public void setProduct(Product product)
     {
           this.product = product;
     }
     public Product getProduct()
     {
           return this.product;
     }
     // count的setter和getter方法
     public void setCount(int count)
     {
           this.count = count;
     }
     public int getCount()
     {
           return this.count;
     }
     // 重写equals()方法，根据product、order、count判断是否相等
     public boolean equals(Object obj)
     {
           if(this == obj)
           {
                return true;
           }
           if(obj != null && obj.getClass() == OrderItem.class)
           {
                OrderItem target = (OrderItem)obj;
                return this.order.equals(target.getOrder())
                     &&  this.product.equals(target.getProduct())
                     && this.count == target.getCount();
           }
           return false;
     }
     // 重写hashCode()方法，根据product、order、count计算hashCode值
     public int hashCode()
     {
           return (this.product == null ? 0 :  this.product.hashCode()) * 31 * 31
                + (this.order == null ? 0 : this.order.hashCode()) * 31
                + this.count;
     }
}

三 测试

1 工具类

package lee;

import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.service.*;
import org.hibernate.boot.registry.*;

public class HibernateUtil
{
    public static final SessionFactory sessionFactory;

    static
    {
        try
        {
            // 使用默认的hibernate.cfg.xml配置文件创建Configuration实例
            Configuration cfg = new Configuration()
                .configure();
            // 以Configuration实例来创建SessionFactory实例
            ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                .applySettings(cfg.getProperties()).build();
            sessionFactory = cfg.buildSessionFactory(serviceRegistry);
        }
        catch (Throwable ex)
        {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    // ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
    public static final ThreadLocal session
        = new ThreadLocal();

    public static Session currentSession()
        throws HibernateException
    {
        Session s = session.get();
        // 如果该线程还没有Session,则创建一个新的Session
        if (s == null)
        {
            s = sessionFactory.openSession();
            // 将获得的Session变量存储在ThreadLocal变量session里
            session.set(s);
        }
        return s;
    }

    public static void closeSession()
        throws HibernateException
    {
        Session s = session.get();
        if (s != null)
            s.close();
        session.set(null);
    }
}

2 测试类

package lee;

import org.hibernate.Transaction;
import org.hibernate.Session;

import java.util.*;
import org.crazyit.app.domain.*;

public class OrderManager
{
    public static void main(String[] args)
    {
        OrderManager mgr = new OrderManager();
        mgr.createAndStoreOrder();
        HibernateUtil.sessionFactory.close();
    }
    private void createAndStoreOrder()
    {
        Session sess = HibernateUtil.currentSession();
        Transaction tx = sess.beginTransaction();

        Order order = new Order(new Date());
        Product p1 = new Product("键盘");
        Product p2 = new Product("显示器");
        OrderItem item1 = new OrderItem(order , p1 , 50);
        OrderItem item2 = new OrderItem(order , p2 , 18);

        sess.save(order);
        sess.save(p1);
        sess.save(p2);
        sess.save(item1);
        sess.save(item2);

        tx.commit();
        HibernateUtil.closeSession();
    }
}

四 测试

Hibernate:
    insert
    into
        order_inf
        (orderDate)
    values
        (?)
Hibernate:
    insert
    into
        product_inf
        (name)
    values
        (?)
Hibernate:
    insert
    into
        product_inf
        (name)
    values
        (?)
Hibernate:
    insert
    into
        order_item_inf
        (product_id, order_id, count)
    values
        (?, ?, ?)
Hibernate:
    insert
    into
        order_item_inf
        (product_id, order_id, count)
    values
        (?, ?, ?)