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，同数据库里的相同。必须在getter方法上标注。



@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

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