Servlets EJB有状态会话Bean和Servlet的问题

我有一个servlet代码，它调用ejb有状态会话bean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*标记之间的线的情况下运行良好。但是，当我在这一行添加SessionBeanSFRemote sessionBeanSF=lookupSessionBeanSFRemote（）时（意味着调用有状态会话Bean），代码给出了错误。实际上，我必须调用无状态会话bean来执行一些工作。有人能帮我解释一下为什么会这样吗？提前谢谢

错误消息如下：

键入异常报告消息

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

例外情况

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

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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.

根本原因

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

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

java.lang.reflect.InvocationTargetException

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]]

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]]

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

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开源版本3.0.1

我不确定您是否正确设置了有状态bean。您可以尝试以下方法：

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

然后，您可以使用以下内容进行查找：

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

此外，应将此有状态bean保存到每个客户端的会话中，以便重新使用：

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

---

在以后的请求中，您可以在为客户机创建新的bean之前，首先尝试从客户机会话中获取bean。

您需要告诉我们您得到的错误。我们不是算命师：豆豆是有状态的还是无状态的？如果它是有状态的，您应该在每个请求中查找一个新实例，而不是在所有请求中共享一个唯一的实例。@JB niset，bean是有状态的。顺便说一句，你能再解释一下吗，这意味着我必须要做的事情。有状态bean用于维护与1个用户的对话状态。查找有状态bean并将其存储在servlet字段中。servlet是一个单例：如果应用程序的所有用户同时使用，则为同一实例。您应该声明bean并在processRequest方法中查找它（并可能将其存储在HTTP会话中）。谢谢。顺便说一句，你的意思是像我问题的更新代码一样的代码？谢谢。顺便说一句，你的意思是像我问题的更新代码一样的代码？不，这显然不是他所建议的。您的异常是由传递给lookup（）的名称不正确引起的。您根本没有更改名称。“remote”表示使用了远程接口，但使用模式表示使用了本地bean。另外，您不需要mappedName。@MikeBraun：我的示例只是一个如何查找有状态bean的示例。我并不是建议他应该或者不应该使用远程接口。此外，

mappedName

是绝对必需的。它是

lookup

方法的参数。@Mr.J4mes您认为为什么需要mappedName，以及为什么在lookup方法中需要它？