java - 为什么我得到 java.lang.ExceptionInInitializerError 以及如何摆脱它？

Question

我正在使用谷歌应用引擎制作一个网络应用程序。我以前没有使用 GWT。但出于某种原因，现在我想使用 Window.Location.getHref()。我添加了 GWT SDK 和所有 gwt jars 文件。但是现在当我调用 Window.Location.getHref() 时，我得到了 java.lang.ExceptionInInitializerError。这是日志:

  2011-08-23 01:17:22.193 /indexpage 500 543ms 1423cpu_ms 0kb Mozilla/5.0 (Macintosh; U;      Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
  90.230.245.85 - - [23/Aug/2011:01:17:22 -0700] "GET /indexpage HTTP/1.1" 500 0 "http://runnotest.appspot.com/" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1" "runnotest.appspot.com" ms=544 cpu_ms=1423 api_cpu_ms=0 cpm_usd=0.039580 instance=00c61b117c2bd11a01e44ceafe4dc9ee198fb4
  W 2011-08-23 01:17:22.183
  Error for /indexpage
  java.lang.ExceptionInInitializerError
at com.google.gwt.user.client.Window$Location.getHash(Window.java:172)
at com.eplinovo.runno3test.mahmood.action.IndexPageServlet.doGet(IndexPageServlet.java:27)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:262)
at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9819)
at com.google.net.rpc.impl.RpcUtil.handleRequest(RpcUtil.java:445)
at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:414)
at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:579)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:454)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:694)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:332)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:324)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:452)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)
  Caused by: java.lang.UnsupportedOperationException: ERROR: GWT.create() is only usable in client code!  It cannot be called, for example, from server code.  If you are running a unit test, check that your test case extends GWTTestCase and that GWT.create() is not called from within an initializer or constructor.
at com.google.gwt.core.client.GWT.create(GWT.java:92)
at com.google.gwt.user.client.Window.<clinit>(Window.java:508)
... 38 more
  W 2011-08-23 01:17:22.185
  Nested in java.lang.ExceptionInInitializerError:
  java.lang.UnsupportedOperationException: ERROR: GWT.create() is only usable in client code!  It cannot be called, for example, from server code.  If you are running a unit test, check that your test case extends GWTTestCase and that GWT.create() is not called from within an initializer or constructor.
at com.google.gwt.core.client.GWT.create(GWT.java:92)
at com.google.gwt.user.client.Window.<clinit>(Window.java:508)
at com.google.gwt.user.client.Window$Location.getHash(Window.java:172)
at com.eplinovo.runno3test.mahmood.action.IndexPageServlet.doGet(IndexPageServlet.java:27)
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$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
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 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.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
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$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:262)
at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9819)
at com.google.net.rpc.impl.RpcUtil.handleRequest(RpcUtil.java:445)
at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:414)
at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:579)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:454)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:694)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:332)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:324)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:452)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)
  C 2011-08-23 01:17:22.186
  Uncaught exception from servlet
  java.lang.ExceptionInInitializerError
at com.google.gwt.user.client.Window$Location.getHash(Window.java:172)
at com.eplinovo.runno3test.mahmood.action.IndexPageServlet.doGet(IndexPageServlet.java:27)
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$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
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 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.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
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$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:262)
at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9819)
at com.google.net.rpc.impl.RpcUtil.handleRequest(RpcUtil.java:445)
at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:414)
at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:579)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:454)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:694)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:332)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:324)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:452)
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)
  Caused by: java.lang.UnsupportedOperationException: ERROR: GWT.create() is only usable in client code!  It cannot be called, for example, from server code.  If you are running a unit test, check that your test case extends GWTTestCase and that GWT.create() is not called from within an initializer or constructor.
at com.google.gwt.core.client.GWT.create(GWT.java:92)
at com.google.gwt.user.client.Window.<clinit>(Window.java:508)
... 38 more

知道为什么我得到 java.lang.ExceptionInInitializerError 以及如何摆脱它吗？提前致谢。

代码如下:

 public class IndexPageServlet extends HttpServlet {
     public void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws IOException {

    resp.setContentType("text/html");
    PrintWriter out = resp.getWriter();

    PersistenceManager pm = PMF.get().getPersistenceManager();

    try
    {

        String token = Window.Location.getHref();
        out.println("Token: " + token);

                    // .... rest of the code

    }
    catch(Exception ex)
    {
         System.out.println("Error fetching runs: " + ex);
    }

    finally
    {
        pm.close();
    }

}
 }

Answer 1

在服务器上，您指的是在静态 block 中调用 GWT.create() 的类。你不能那样做。

您的代码中的问题是 Window.Location.getHref() - 这在服务器上不可用。如果您想获取当前 url，请使用 serlvet api 中的 request.getRequestURL()。

您无法访问服务器上的 anchor 参数 (#foo)。它们不是从客户端发送的。您必须在客户端解析它们并将它们作为请求参数发送。