Java 应用程序引擎中的HTTP 500内部服务器错误

此代码写入数据存储

    package pack.exp;
    @SuppressWarnings("serial")
    public class WriteServlet extends HttpServlet 
    {
         public void doGet(HttpServletRequest req, HttpServletResponse resp) throws...
     {
    Entity ent= new Entity("Employee", "E");
    ent.setProperty("FirstName", "Agent");
    ent.setProperty("LastName", "47");

    DatastoreService ds= DatastoreServiceFactory.getDatastoreService();
    ds.put(ent);

    resp.setContentType("text/plain");
    resp.getWriter().println("File Saved");
    }
     }

     package pack.exp;
     @SuppressWarnings("serial")
     public class ReadServlet extends HttpServlet 
     {
         @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws  
      {
          super.doGet(req, resp);

          DatastoreService ds= DatastoreServiceFactory.getDatastoreService();

      Key k= KeyFactory.createKey("Employee", "E");

    try 
    {
        Entity ent= ds.get(k);

        String fN= (String) ent.getProperty("FirstName");
        String lN= (String) ent.getProperty("LastName");

        resp.setContentType("text/plain");
        resp.getWriter().println("Reading From the Database " + fN );

    }

    catch (EntityNotFoundException e)
    {
        e.printStackTrace();
    }
     }
      }

这是用于从数据存储中读取的

    package pack.exp;
    @SuppressWarnings("serial")
    public class WriteServlet extends HttpServlet 
    {
         public void doGet(HttpServletRequest req, HttpServletResponse resp) throws...
     {
    Entity ent= new Entity("Employee", "E");
    ent.setProperty("FirstName", "Agent");
    ent.setProperty("LastName", "47");

    DatastoreService ds= DatastoreServiceFactory.getDatastoreService();
    ds.put(ent);

    resp.setContentType("text/plain");
    resp.getWriter().println("File Saved");
    }
     }

     package pack.exp;
     @SuppressWarnings("serial")
     public class ReadServlet extends HttpServlet 
     {
         @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws  
      {
          super.doGet(req, resp);

          DatastoreService ds= DatastoreServiceFactory.getDatastoreService();

      Key k= KeyFactory.createKey("Employee", "E");

    try 
    {
        Entity ent= ds.get(k);

        String fN= (String) ent.getProperty("FirstName");
        String lN= (String) ent.getProperty("LastName");

        resp.setContentType("text/plain");
        resp.getWriter().println("Reading From the Database " + fN );

    }

    catch (EntityNotFoundException e)
    {
        e.printStackTrace();
    }
     }
      }

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当我部署应用程序时，它会显示appspot页面，但当我单击我的项目时，它会在App Engine中显示HTTP 500内部服务器错误

您使用的是GAE不支持的AWT的某些部分（没有窗口UI）。删除该库/包或使用它的任何包

---

顺便说一句，这个错误也应该出现在dev服务器上。在部署之前，您将节省大量在开发服务器上进行本地测试的时间。

可能是重复的，我无法检测到错误。错误日志显示了什么？检索KeyboardFocusManagerPeerProvider[在KeyboardFocusManagerPeerProvider.class[在sun.awt中]的KeyboardFocusManagerPeerProvider.class中]的附加javadoc时，内部错误超时[在C:\Program Files\Java\jre7\lib\rt.jar]]检索代理{key=Lsun/management/Agent；}[在Agent.class[在sun.management[在C:\Program Files\Java\jre7\lib\rt.jar]]的附加javadoc时，内部错误超时[在C:\Program Files\jre7\lib\rt.jar]]中我没有使用额外的包。为什么堆栈跟踪显示正在加载AWT？