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Jboss Ejb3.0 Entity Bean

Order.java

package org.jboss.tutorial.entity.bean;

import javax.persistence.CascadeType;

import javax.persistence.Entity;

import javax.persistence.FetchType;

import javax.persistence.GeneratorType;

import javax.persistence.Id;

import javax.persistence.OneToMany;

import javax.persistence.Table;

import javax.persistence.Id;

import javax.persistence.CascadeType;

import javax.persistence.FetchType;

import java.util.ArrayList;

import java.util.Collection;

@Entity

@Table(name = "PURCHASE_ORDER")

//If the table name isn\\\'t specified it defaults to the bean name

//of the class. For instance, the LineItem EJB would be mapped to

//the LINEITEM table

public class Order implements java.io.Serializable

{

   private int id;

   private double total;

   private Collection<LineItem> lineItems;

   @Id(generate = GeneratorType.AUTO)

   public int getId()

   {

      return id;

   }

   public void setId(int id)

   {

      this.id = id;

   }

   public double getTotal()

   {

      return total;

   }

   public void setTotal(double total)

   {

      this.total = total;

   }

   public void addPurchase(String product, int quantity, double price)

   {

      if (lineItems == null) lineItems = new ArrayList<LineItem>();

      LineItem item = new LineItem();

      item.setOrder(this);

      item.setProduct(product);

      item.setQuantity(quantity);

      item.setSubtotal(quantity * price);

      lineItems.add(item);

      total += quantity * price;

   }

   //CascadeType.ALL specifies that when an Order is created,

   //any LineItems held in the lineItems collection will be created

   //as well (CascadeType.PERSIST). If the Order is delete from

   //persistence storage, all related LineItems will be

   //deleted (CascadeType.REMOVE). If an Order instance is

   //reattached to persistence storage, any changes to the

   //LineItems collection will be merged with persistence

   //storage (CascadeType.MERGE).

   //FetchType.EAGER specifies that when the Order is loaded

   //whether or not to prefetch the relationship as well.

   //If you want the LineItems to be loaded on demand, then specify FetchType.LAZY.

   //   The mappedBy attribute specifies that this is a bi-directional

   //relationship that is managed by the order property on the LineItem entity bean.

   @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy="order")

   public Collection<LineItem> getLineItems()

   {

      return lineItems;

   }

   public void setLineItems(Collection<LineItem> lineItems)

   {

      this.lineItems = lineItems;

   }

}

加了不少英文注释，希望能看得懂。

@Table(name = "PURCHASE_ORDER")

指名数据库（jboss的数据库为hsqldb）中对应得表的名字，默认为class的名字，比如下面的LineItem就没有@table。（order.java , LineItem.java都为o/r映射，值得互相对照）

@Id(generate = GeneratorType.AUTO)

递增，同数据库里的一样。必须在getter方式上标注。

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy="order")

关系：order和LineItem为1对多的关系。在这里CascadeType.ALL是指明当建立一个Order被实例化后，都应该同时同时建立LineItem。注释里的就是根据两者建立时间的不同，定义了不同的CascadeType。

LineItem.java

package org.jboss.tutorial.entity.bean;

import javax.persistence.Entity;

import javax.persistence.GeneratorType;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

import javax.persistence.Entity;

@Entity

public class LineItem implements java.io.Serializable

{

   private int id;

   private double subtotal;

   private int quantity;

   private String product;

   private Order order;

   @Id(generate = GeneratorType.AUTO)

   public int getId()

   {

      return id;

   }

   public void setId(int id)

   {

      this.id = id;

   }

   public double getSubtotal()

   {

      return subtotal;

   }

   public void setSubtotal(double subtotal)

   {

      this.subtotal = subtotal;

   }

   public int getQuantity()

   {

      return quantity;

   }

   public void setQuantity(int quantity)

   {

      this.quantity = quantity;

   }

   public String getProduct()

   {

      return product;

   }

   public void setProduct(String product)

   {

      this.product = product;

   }

   //The @JoinColumn specifies the foreign key column within the LineItem table.

   @ManyToOne

   @JoinColumn(name = "order_id")

   public Order getOrder()

   {

      return order;

   }

   public void setOrder(Order order)

   {

      this.order = order;

   }

}

ShoppingCart.java

package org.jboss.tutorial.entity.bean;

import javax.ejb.Remote;

import javax.ejb.Remove;

@Remote

public interface ShoppingCart

{

   void buy(String product, int quantity, double price);

   Order getOrder();

   @Remove void checkout();

}

ShoppingCartBean.java

package org.jboss.tutorial.entity.bean;

import javax.persistence.EntityManager;

import javax.ejb.Inject;

import javax.ejb.Remove;

import javax.ejb.Stateful;

@Stateful

public class ShoppingCartBean implements ShoppingCart

{

   @Inject

   private EntityManager manager;       //The EntityManager is used to do querying,

//creating, find by primary key, and removal of entity beans.

   private Order order;

   public void buy(String product, int quantity, double price)

   {

      if (order == null) order = new Order();

      order.addPurchase(product, quantity, price);

   }

   public Order getOrder()

   {

      return order;

   }

   @Remove

   public void checkout()

   {

      manager.persist(order);

   }

}

EntityManager的作用可大了，可以用于查询，创建，删除实体Bean,这里插入个EntityManager,主要是在最后用户离开时，在数据库里保存数据，相称于保存个object。运行完Client.java后就可以在hsqldb上看到有purchase_order 和 LineItem 的两张表。HypersonicDatabase ，找到startDatabaseManager然后下面有个invoke,点击就可以访问hsqldb了。

Client.java

package org.jboss.tutorial.entity.client;

import org.jboss.tutorial.entity.bean.LineItem;

import org.jboss.tutorial.entity.bean.Order;

import org.jboss.tutorial.entity.bean.ShoppingCart;

import javax.naming.InitialContext;

public class Client

{

   public static void main(String[] args) throws Exception

   {

      InitialContext ctx = new InitialContext();

      ShoppingCart cart = (ShoppingCart) ctx.lookup(ShoppingCart.class.getName());

      System.out.println("Buying 2 memory sticks");

      cart.buy("Memory stick", 2, 500.00);

      System.out.println("Buying a laptop");

      cart.buy("Laptop", 1, 2000.00);

      System.out.println("Print cart:");

      Order order = cart.getOrder();

      System.out.println("Total: $" + order.getTotal());

      for (LineItem item : order.getLineItems())

      {

         System.out.println(item.getQuantity() + "     " + item.getProduct() + "     " + item.getSubtotal());

      }

      System.out.println("Checkout");

      cart.checkout();

   }

}

这里附上log4j.properties 在jboss-EJB-3.0_Preview_5.zip　里面没有这个老是显示缺少appender。有了这个将在该目录下生成个record.log日志文件。

log4j.properties

log4j.appender.R=org.apache.log4j.RollingFileAppender

log4j.appender.R.File=record.log

log4j.appender.R.layout=org.apache.log4j.PatternLayout

log4j.appender.R.layout.ConversionPattern=%p %d{hh:mm:ss} %t %c{1} -%m%n

log4j.appender.R.MaxBackupIndex=1

log4j.appender.R.MaxFileSize=100KB

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) -%m%n

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.rootLogger=stdout,R

运行：参考installing.html

Windows下

打开命令提示符cmd，到 jboss_home/bin

Run.bat –c all

用ant

先build后run 就行了。

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