我已经按照此处的说明为 Juno 安装了 AppEngine Eclipse 插件：https ://developers.google.com/appengine/docs/java/tools/eclipse
但是，当运行一些提供的示例项目（例如 ShardedCounter）时，会抛出 NoClassDefFoundError，说明找不到类 com/google/appengine/tools/development/DevAppServerFactory$CustomSecurityManager$StackTraceAnalyzer：
java.lang.NoClassDefFoundError: com/google/appengine/tools/development/DevAppServerFactory$CustomSecurityManager$StackTraceAnalyzer
at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.appHasPermission(DevAppServerFactory.java:334)
at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:379)
at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:408)
at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:299)
at java.lang.Thread.init(Thread.java:336)
at java.lang.Thread.<init>(Thread.java:608)
at java.util.concurrent.Executors$DefaultThreadFactory.newThread(Executors.java:541)
at com.google.appengine.tools.development.ApiProxyLocalImpl$DaemonThreadFactory.newThread(ApiProxyLocalImpl.java:644)
at java.util.concurrent.ThreadPoolExecutor.addThread(ThreadPoolExecutor.java:672)
at java.util.concurrent.ThreadPoolExecutor.addIfUnderMaximumPoolSize(ThreadPoolExecutor.java:721)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:657)
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:92)
at com.google.appengine.tools.development.ApiProxyLocalImpl$PrivilegedApiAction.run(ApiProxyLocalImpl.java:270)
at com.google.appengine.tools.development.ApiProxyLocalImpl$PrivilegedApiAction.run(ApiProxyLocalImpl.java:255)
at com.google.appengine.tools.development.ApiProxyLocalImpl.makeAsyncCall(ApiProxyLocalImpl.java:203)
at com.google.apphosting.api.ApiProxy.makeAsyncCall(ApiProxy.java:190)
at com.google.appengine.api.datastore.DatastoreApiHelper.makeAsyncCall(DatastoreApiHelper.java:56)
at com.google.appengine.api.datastore.PreparedQueryImpl.runQuery(PreparedQueryImpl.java:127)
at com.google.appengine.api.datastore.PreparedQueryImpl.asIterator(PreparedQueryImpl.java:60)
at com.google.appengine.api.datastore.BasePreparedQuery$1.iterator(BasePreparedQuery.java:25)
at com.google.appengine.demos.shardedcounter.java.v1.ShardedCounter.getCount(ShardedCounter.java:59)
at com.google.appengine.demos.shardedcounter.java.v1.CounterPage.doGet(CounterPage.java:36)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$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:368)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:351)
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:485)
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$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
我对示例项目所做的唯一修改是删除了 Google Web Toolkit 的使用，因为如果使用 GWT，则无法启动测试服务器。我刚刚开始尝试 AppEngine，非常感谢任何帮助。