GWT錯誤：java.lang.NoClassDefFoundError：com / google / gwt / core / client / GWTBridge

Question

我正在將GWT用於一個類項目，盡管以前一切正常，但最近我重構了代碼，突然遇到標題錯誤。 我四處搜尋，看來GWTBridge問題是由2大問題引起的：a）一個針對2.5.1修復的錯誤，或b）試圖從服務器調用客戶端代碼，反之亦然（ classNotFoundException GWTBridge ）。

我使用的是GWT 2.5.1，我99％的確定自己沒有違反情況b），所以我很茫然。 我實際上只是在重構時從工作版本中復制和粘貼代碼，所以我不確定問題出在哪里。

我的直覺是，它可能與重構時創建的兩個靜態Singleton類有關。 重構時，我的目標只是使RPC少些混亂，因為它迫使我束縛一堆異步調用，這使我發瘋。 我基本上要做的是制作兩個靜態的Singleton類（PageLoader和UserManager），其目的是進行異步調用並返回OnSuccess返回的內容，因此在onModuleLoad中，我可以進行連續的RPC調用而不必處理鏈接（例如，我可以只需轉到UserManager.getInstance（）。isLoggedIn（），然后稍后在RPC調用中使用返回的布爾值，而不必將該調用放入onSuccess函數中）。 我將這兩個類與Async類一起放在了client.services中。

我不知道為什么會引起問題，但我想不出其他任何事情。 知道我走的路是否正確嗎？

我在下面附加了靜態類之一和返回的堆棧跟蹤的一部分。

---

UserManager類別

package com.google.gwt.sample.vendorcouver.client.services;

import com.google.gwt.core.client.GWT;
import com.google.gwt.sample.vendorcouver.client.user.VenUser;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.rpc.AsyncCallback;


/*Singleton that simplifies making asynchronous calls to the server side.*/

public class UserManager {

    private static UserManager UserManagerInstance = null;
    private static LoginServiceAsync LoginServiceInstance = null;
    private static VenUserServiceAsync VenUserServiceInstance = null;
    private static boolean isLoggedIn = false;
    private static boolean isAdmin = false;
    private static String UserName = null;


    public static UserManager getInstance()
    {
        if (UserManagerInstance == null)
        {
            UserManagerInstance = new UserManager();
            LoginServiceInstance = GWT.create(LoginService.class);
            VenUserServiceInstance = GWT.create(VenUserService.class);
        }
        return UserManagerInstance;
    }

    public boolean isLoggedIn()
    {
        LoginServiceInstance.isLoggedIn(new AsyncCallback<Boolean>() {
            public void onFailure(Throwable error) {
                Window.alert("Sorry, there seemed to be an error on the server side! You may be unable to log in.");
            }
            public void onSuccess(Boolean loggedInStatus) {
                Window.alert("isLoggedIn is sucessful; will return" + loggedInStatus);
                isLoggedIn = loggedInStatus;
            }
        });
        return isLoggedIn;
    }

堆棧跟蹤：

   SEVERE: javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract boolean com.google.gwt.sample.vendorcouver.client.services.LoginService.isLoggedIn()' threw an unexpected exception: java.lang.NoClassDefFoundError: com/google/gwt/core/client/GWTBridge
    at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:97)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:487)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.lang.NoClassDefFoundError: com/google/gwt/core/client/GWTBridge
    at com.google.gwt.user.client.Window.<clinit>(Window.java:504)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at com.google.appengine.tools.development.agent.runtime.RuntimeHelper.checkRestricted(RuntimeHelper.java:70)
    at com.google.appengine.tools.development.agent.runtime.Runtime.checkRestricted(Runtime.java:64)
    at com.google.gwt.sample.vendorcouver.server.LoginServiceImpl.isLoggedIn(LoginServiceImpl.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:115)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:561)
    ... 40 more
Caused by: java.lang.ClassNotFoundException: com.google.gwt.core.client.GWTBridge
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:216)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 52 more

Answer 1

堆棧跟蹤很清楚：您正在嘗試使用com.google.gwt.sample.vendorcouver.server.LoginServiceImpl#isLoggedIn （服務器端代碼）中的com.google.gwt.user.client.Window （客戶端）類。

---

順便說一句，您確實意識到您的UserManager#isLoggedIn 總是在第一次調用時返回false ，對嗎？ （由於RPC調用的異步性質）

Answer 2

在您的項目中添加以下內容（確保軟件包正確）：

package com.google.gwt.core.client;
import com.google.gwt.core.shared.*;
/**
* Date: 1/17/13
* Time: 12:37 PM
* This class is used for fixing class not found com.google.gwt.core.client.GWTBridge;
*
* This is only needed for GXT 2 to work. Once we remove GXT2, this can be removed also.
*/
public abstract class GWTBridge extends com.google.gwt.core.shared.GWTBridge {
}

原文： http ： //alexluca.com/2013/01/17/gwt-25-and-extgwt-224-classnotfoundexception-comgooglegwtcoreclientgwtbridge/

Answer 3

不允許在服務器端使用Window.alert 。