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我有一个调用 ejb 有状态会话 bean 代码的 servlet 代码，如下所示， 

public class UsesBeansSF extends HttpServlet {   
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    try {
          // do something
       }

    finally {}
 } 

private SessionBeanSFRemote lookupSessionBeanSFRemote() {
    try {
        Context c = new InitialContext();
        return (SessionBeanSFRemote) c.lookup("java:global/MyEJBSF/SessionBeanSF!ejbSF.SessionBeanSFRemote");
    } catch (NamingException ne) {
        Logger.getLogger(getClass().getName()).log(Level.SEVERE, "exception caught", ne);
        throw new RuntimeException(ne);
    }
}

}

此代码在没有 * 标记之间的情况下运行良好。但是，当我添加SessionBeanSFRemote sessionBeanSF = lookupSessionBeanSFRemote()这一行（意味着调用有状态会话 Bean）时，代码给出了错误。实际上，我必须调用无状态会话 bean 才能执行某些工作。谁能帮助我为什么会这样？提前致谢。

错误信息如下：

类型异常报告消息

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

例外

javax.servlet.ServletException: PWC1392: Error instantiating servlet class websSF.comsSF.UsesBeansSF

根本原因

com.sun.enterprise.container.common.spi.util.InjectionException: 
         Error creating managed object for class websSF.comsSF.UsesBeansSF

根本原因

java.lang.reflect.InvocationTargetException

根本原因

java.lang.RuntimeException: javax.naming.NamingException: 
Lookup failed for 'java:global/MyEJBSF/SessionBeanSF!ejbSF.SessionBeanSFRemote' in SerialContext  
[Root exception is javax.naming.NamingException: 
ejb ref resolution error for remote business interfaceejbSF.SessionBeanSFRemote [Root exception is java.lang.NullPointerException]]

根本原因

javax.naming.NamingException: 
Lookup failed for 'java:global/MyEJBSF/SessionBeanSF!ejbSF.SessionBeanSFRemote' in SerialContext  
[Root exception is javax.naming.NamingException: 
ejb ref resolution error for remote business interfaceejbSF.SessionBeanSFRemote
[Root exception is java.lang.NullPointerException]]

根本原因

javax.naming.NamingException: ejb ref resolution error for remote business 
interfaceejbSF.SessionBeanSFRemote [Root exception is java.lang.NullPointerException]

根本原因

java.lang.NullPointerException
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.0.1 logs.

服务器：GlassFish Server 开源版 3.0.1

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1 回答 1

3

我不确定您是否正确设置了有状态 bean。你可以试试这个：

@Stateful(mappedName = "ejb/myStatefulBean")
public class MyStatefulBean implements MyStatefulRemoteInterface {
   // Your implementation
}

然后您可以使用以下方法查找它：

InitialContext context = new InitialContext();
MyStatefulRemoteInterface myStatefulBean = (MyStatefulRemoteInterface) context.lookup("ejb/myStatefulBean");

Besides, this stateful bean should be saved into each client's session for re-using:

HttpSession clientSession = request.getSession(false);
clientSession.setAttribute("myStatefulBean", myStatefulBean);

In future requests, you can try to get the bean from the client' session first before creating a new one for him.

于 2012-01-01T11:35:12.243 回答