我已经使用 Maven 的原型创建了 Google 的示例留言簿项目com.google.appengine.archetypes:guestbook-archetype。当我使用它在本地运行它时，mvn appengine:devserver它工作正常，当我尝试将它部署在 Google 的 Appspot 上时，问题就开始了。我收到以下消息：
Error: Server Error
The server encountered an error and could not complete your request.
If the problem persists, please report your problem and mention this error message and the query that caused it.
在日志中我可以看到：
2013-05-01 05:38:28.356 / 500 3166ms 0kb Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31
2001:6d8:10:a014:5176:bdbe:c152:53c0 - - [01/May/2013:05:38:28 -0700] "GET / HTTP/1.1" 500 0 - "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31" "aghinzop.appspot.com" ms=3167 cpu_ms=2100 loading_request=1 app_engine_release=1.7.7 instance=00c61b117cdf51947e909cbfaf52e1739a7f4c
W 2013-05-01 05:38:28.325
EXCEPTION
java.lang.ClassNotFoundException: ioserv.ioserv.SignGuestbookServlet
at com.google.appengine.runtime.Request.process-53e8711216f37199(Request.java)
at java.lang.ClassLoader.loadClass(ClassLoader.java:359)
at org.mortbay.util.Loader.loadClass(Loader.java:91)
at org.mortbay.util.Loader.loadClass(Loader.java:71)
at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:73)
at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at java.lang.Thread.run(Thread.java:722)
E 2013-05-01 05:38:28.326
javax.servlet.ServletContext log: unavailable
javax.servlet.UnavailableException: ioserv.ioserv.SignGuestbookServlet
at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:79)
at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:219)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:194)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:438)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:722)
W 2013-05-01 05:38:28.338
Failed startup of context com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@11c3e97{/,/base/data/home/apps/s~aghinzop/1.367061823227494749}
java.lang.NullPointerException
at java.lang.Class.isAssignableFrom(Native Method)
at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:256)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:219)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:194)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:438)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:722)
C 2013-05-01 05:38:28.342
Uncaught exception from servlet
javax.servlet.UnavailableException: Initialization failed.
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:228)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:194)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:438)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:722)
I 2013-05-01 05:38:28.355
This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application.
这是我在 Eclipse 中的基本设置和部署日志（我使用 App Engine Eclipse 插件）。
我不确定“因为这是一个 Maven 项目而被禁用”是什么意思。你能解释一下吗？我应该选中这个框吗？
这里选择的 App Engine SDK 是 Eclipse Plugin 提供的。
这是插件提供的库。原型还添加了一些 Maven 库。
这是 WEB-INF/lib 中的库。我可以看到它们很少，我意识到可能缺少一些东西。问题是当我尝试将库复制到这个文件夹中时，我得到了Cannot paste the clipboard contents into the selected elements. 我怎样才能做到这一点？在普通的动态 Web 项目（使用这个方面）中，它很简单，Properties>Deployment Assembly>Add但在这里我不知道如何做到这一点。
我真的很感谢你的帮助！谢谢！