本文是我用EJB+JPA(Hibernate實(shí)現(xiàn))+Web Service開發(fā)時，遇到的一些問題，查了許多地方，都找不到答案，請各位朋友耐心讀一下本文，有想法的歡迎留言！謝謝！ 

    Category.java的部分代碼：

	@OneToMany(cascade={CascadeType.ALL},fetch=FetchType.LAZY,mappedBy="category")
public List<News> getNewsList() {
return newsList;
}
public void setNewsList(List<News> newsList) {
this.newsList = newsList;
}

    News.java的部分代碼：

	@ManyToOne(cascade={CascadeType.PERSIST,CascadeType.MERGE},fetch=FetchType.EAGER)
@JoinColumn(name="cid")
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}

   NewsDaoBean.java的部分代碼：

	@PersistenceContext(unitName="newspstn")
private EntityManager em;
/**
* 添加新聞
* @param cid 項目編號
* @param news
*/
public void saveNews(int cid,News news) {
news.setCategory(em.find(Category.class, cid));
em.persist(news);
}
/**
* 查詢所有新聞列表
* @return
*/
@SuppressWarnings("unchecked")
public List<News> listNews() {
return (List<News>)em.createQuery("from News n").getResultList();
}

    業(yè)務(wù)邏輯層的類（NewsManager.java）比較簡單，由于篇幅問題，這里就不貼出來了。

    在還沒有發(fā)布成Web Service前，用Juint測試：

                //測試保存新聞
public void testSaveNews() {
InitialContext ctx;
try {
ctx = new InitialContext();
NewsManager manager = (NewsManager)ctx.lookup("NewsManagerBean/remote");
News news = new News();
news.setTitle("title2");
news.setAuthor("author2");
news.setContent("content1");
manager.saveNews(1, news);
} catch (NamingException e) {
System.out.println("NamingException");
e.printStackTrace();
}
}
//測試查詢新聞列表
public void testListNews() {
InitialContext ctx;
try {
ctx = new InitialContext();
NewsManager manager = (NewsManager)ctx.lookup("NewsManagerBean/remote");
List<News> newsList = manager.listNews();
for(News news : newsList){
System.out.println("news.title = " + news.getTitle());
}
} catch (NamingException e) {
System.out.println("NamingException");
e.printStackTrace();
}
}

   這個測試是沒有問題的，(testSaveNews和testListNews)能正常添加和查詢。

    當(dāng)發(fā)布成Web Service后，在客戶端生成相應(yīng)的服務(wù)代理類，再在Web服務(wù)的客戶端用Junit測試：

	//測試保存新聞
@Test
public void testSaveNews(){
NewsManagerService service = new NewsManagerService();
NewsManager manager = service.getNewsManagerPort();
News news = new News();
news.setTitle("title1");
news.setAuthor("author1");
news.setContent("content1");
manager.saveNews(1, news);
}
//測試查詢新聞列表
@Test
public void testListNews(){
NewsManagerService service = new NewsManagerService();
NewsManager manager = service.getNewsManagerPort();
List<News> newsList = manager.listNews();     //------a1
for(News news : newsList) {                             //--------a2
System.out.println("news.title = " + news.getTitle());   //----a3
}                         //------a4
}

    這次測試，保存新聞的的操作（testSaveNews）能正常，但查詢新聞列表（testListNews）的操作卻拋以下異常：

12:19:37,781 INFO  [STDOUT] Hibernate:
select
news0_.id as id1_,
news0_.content as content1_,
news0_.cid as cid1_,
news0_.title as title1_,
news0_.author as author1_,
news0_.pubtime as pubtime1_
from
rong_news news0_
12:19:37,781 INFO  [STDOUT] Hibernate:
select
category0_.id as id0_0_,
category0_.cname as cname0_0_
from
rong_category category0_
where
category0_.id=?
12:19:37,796 ERROR [LazyInitializationException] failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
（……相關(guān)的異常堆棧信息略……）
12:19:37,796 ERROR [RequestHandlerImpl] Error processing web service request
org.jboss.ws.WSException: javax.xml.ws.WebServiceException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
（……相關(guān)的異常堆棧信息略……）
Caused by: javax.xml.ws.WebServiceException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
（……相關(guān)的異常堆棧信息略……）
Caused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
（……相關(guān)的異常堆棧信息略……）
12:19:37,890 ERROR [[NewsManagerBean]] Servlet.service() for servlet NewsManagerBean threw exception
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: rong.entity.Category.newsList, no session or session was closed
（……相關(guān)的異常堆棧信息略……）

補(bǔ)充說明1：如果我把上面testListNews方法中的a1,a2,a3,a4行注釋掉，Junit測試是正常的。

補(bǔ)充說明2：在Category類中，對List<News> newsList的設(shè)置，我確定是設(shè)置了延遲加載(Lazy)的，而且，我在查詢 新聞列表時，沒有用到news.getCategory.getNewsList()之類的操作。有個疑問：是不是設(shè)置的lazy加載，即使沒有用到，也會加載的？即使會加載的，為什么我在服務(wù)器端測試時能正常，而在Web Service的客戶端測試時，卻報錯？

是EJB Web Service的Bug還是我的程序有錯誤？請大家討論！