NoClassDefFoundError - restricted class on GAE/J

Simply put, when deploying my (Java) app to GAE, GAE throws an java.lang.NoClassDefFoundError for a class in one of the bundled jars. Everything worked fine in my test-environment.

The exception is:

java.lang.NoClassDefFoundError: org.jcp.xml.dsig.internal.dom.XMLDSigRI is a restricted class. Please see the Google App Engine developer's guide for more detail开发者_StackOverflows.

But running jar -tf xmlsec-1.4.0.jar shows the "missing" class clearly to be present in the jar.

Why would this class be "restricted"? How can I find out the cause? I am running 3rd-party servlets which require this package (and this class) to work. ( http://sourceforge.net/projects/saml2api/ ) What to do?

Here follows the complete error message from GAE:

Uncaught exception from servlet
java.lang.NoClassDefFoundError: org.jcp.xml.dsig.internal.dom.XMLDSigRI is a restricted class. Please see the Google App Engine developer's guide for more details.
    at com.google.apphosting.runtime.security.shared.stub.org.jcp.xml.dsig.internal.dom.XMLDSigRI.<clinit>(XMLDSigRI.java)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at java.lang.Class.newInstance0(Unknown Source)
    at java.lang.Class.newInstance(Unknown Source)
    at org.eclipse.higgins.saml2idp.saml2.XMLElement.<clinit>(XMLElement.java:95)
    at no.ntnu.it.fw.saml2api.SAML2Util.createSAMLAuthnRequest(SAML2Util.java:180)
    at no.ntnu.it.fw.saml2api.http.LoginServlet.doExecute(LoginServlet.java:184)
    at no.ntnu.it.fw.saml2api.http.LoginServlet.doPost(LoginServlet.java:71)
    at no.ntnu.it.fw.saml2api.http.LoginServlet.doGet(LoginServlet.java:65)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
    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:238)
    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$RequestHandler.headerComplete(HttpConnection.java:923)
    at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:250)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:7115)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:7113)
    at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:398)
    at com.google.net.rpc.impl.Server$2.run(Server.java:852)
    at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56)
    at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:576)
    at com.google.net.rpc.impl.Server.startRpc(Server.java:807)
    at com.google.net.rpc.impl.Server.processRequest(Server.java:369)
    at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:442)
    at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319)
    at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290)
    at com.google.net.async.Connection.handleReadEvent(Connection.java:474)
    at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:831)
    at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:207)
    at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:103)
    at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251)
    at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:417)
    at java.lang.Thread.run(Unknown Source)

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Take a look at the Sandbox restrictions. The stack trace is showing java.lang.reflect so there is probably an issue related to Sandbox restrictions and reflection.