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javagoogle-app-enginecglib

Cglib Enhancer of HashMap on Google App Engine throws a Class Not Found Exception

I am using cglib to enhance a HashMap so I can intercept method calls on the HashMap.

It works fine on my local computer, and when I run as a google web application within eclipse. Once deployed on the server, however, I am getting an exception "java.lang.NoClassDefFoundError: [Ljava/util/HashMap$Entry;"

The line of code that throws the exception is:

Enhancer.create(HashMap.class, new SomeInterceptor());

I am using the latest plugin for eclipse (3.7). I am using cglib version 2.2 (cglib-nodep-2.2.jar)

EDIT: This is interesting: If I create a class that extends from HashMap, then I can enhance that class without any issues. For example, the following code works:

public class MyHashMap extends HashMap {
}
Enhancer.create(MyHashMap.class, new SomeInterceptor());

And Enhancer works for TreeMap, HashSet, and TreeSet :ENDEDIT

The stack trace is:

java.lang.NoClassDefFoundError: [Ljava/util/HashMap$Entry;
at com.google.appengine.runtime.Request.process-02796318ce7d3a7b(Request.java)
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2444)
at java.lang.Class.getDeclaredMethod(Class.java:229)
at net.sf.cglib.proxy.Enhancer.getCallbacksSetter(Enhancer.java:630)
at net.sf.cglib.proxy.Enhancer.setCallbacksHelper(Enhancer.java:618)
at net.sf.cglib.proxy.Enhancer.setThreadCallbacks(Enhancer.java:612)
at net.sf.cglib.proxy.Enhancer.createUsingReflection(Enhancer.java:634)
at net.sf.cglib.proxy.Enhancer.firstInstance(Enhancer.java:538)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:225)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:663)
at com.enhancetest.EnhanceTestServlet.doGet(EnhanceTestServlet.java:30)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
at java.lang.Thread.run(Thread.java:679)

Caused by: java.lang.ClassNotFoundException: java.util.HashMap$Entry ... 35 more

Solution

  • Perhaps I'm missing something, if it is I'm sorry, but from a quick search I'found this: http://grepcode.com/snapshot/repo1.maven.org/maven2/cglib/cglib/2.2

    It seems that GAE has only a Partial support to cglib... could this be the source of this issue? Furthermore in the official GAE docs for supported Java libraries http://code.google.com/p/googleappengine/wiki/WillItPlayInJava

    CGLIB is not even mentioned.

    EDIT: BTW, I'm assuming that you are importing java.util.HashMap... check you did not import other implementation (like "com.google.gwt.dev.util.collect.HashMap")... somtimes this kind of mistake happens for nothing!