GAE 上出现奇怪的 500 错误

Question

我今天开始在我的应用程序上收到此错误，根本不记得更改任何内容.. 每当我在本地尝试时，它都可以正常工作，但是部署后出现此错误。

EXCEPTION 
java.lang.ClassNotFoundException: se.myApp.server.MyServiceImpl
    at com.google.appengine.runtime.Request.process-bf332e9dcd56cd0b(Request.java)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    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.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

E 2011-04-28 06:42:42.981

javax.servlet.ServletContext log: unavailable
javax.servlet.UnavailableException: se.myApp.server.MyServiceImpl
    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:191)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)


Failed startup of context com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@bd93cd{/,/base/data/home/apps/my_app/1.350039326756879872}
org.mortbay.util.MultiException[java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException]
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:656)
    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:191)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

Uncaught exception from servlet
javax.servlet.UnavailableException: Initialization failed.
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:200)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

每当我从 GWT 执行 RPC 调用时都会抛出它，无论它可能是什么 RPC。 例如，调用 getHello() 会导致这个错误：

/**
 * The server side implementation of the RPC service.
 */
@SuppressWarnings("serial")
public class MyServiceImpl extends RemoteServiceServlet implements
        MyService {

    public String getHello()
    {
        return "Hello";
    }
}

web.xml 长这样，

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
     <servlet>
    <servlet-name>myService</servlet-name>
    <servlet-class>se.myApp.server.MyServiceImpl</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>myService</servlet-name>
    <url-pattern>/etc/myService</url-pattern>
  </servlet-mapping>

  <!-- Default page to serve -->
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>

</web-app>

更新： 获得最新的GAE SDK、GWT SDK后： 尝试将标准 GreetingSample 部署到新的 .appspot.com。问题仍然存在。

更新： 在获取 Eclipse 更新后，错误似乎消失了，但是，每次服务器端代码中出现一个小错误时，让我们说一个拼写错误的查询，而不是抛出一个指向查询的正常错误，我得到了而是上面的错误。

Answer 1

在测试时从我的 IDE 进行快速部署时，这种情况发生过几次。

您可能有一个部分部署的应用程序。

您应该回滚应用程序以确保它没有部分部署，然后重新部署。

当我对我的项目进行 Maven 化并开始使用 maven-gae-plugin 进行部署时，我不再遇到这些问题。

它使部署像mvn clean package gae:deploy 一样简单。它还使回滚变得像mvn gae:rollback 一样简单

我有instructions on setting up Maven 3 for GAE deployment，它也包含 GWT 支持，如果您不使用 GWT，可以将其删除。