Can't instantiate anonymous class more than 16 times

Mon Aug 10 15:19:45 PDT 2009

Le 10/08/2009 23:54, Rémi Forax a écrit :
> Le 10/08/2009 21:56, Wei Yin Teo a écrit :
>> Hi,
>>
>> After loading an anonymous class through the AnonymousClassLoader, I 
>> could construct the object by calling the newInstance on the class. 
>> But the 16th time failed. Here is the code and stack trace
>
> hum, perhaps a bug,
> could you try with :
>
> AnonymousClassLoader acl = new AnonymousClassLoader(LoadingTest.class);
>
> cheers,
> Rémi

Forget what I've written.
I am able to reproduce the bug.
It seems you can't create more than 16 instances of an anonymous class,
a really weird bug, isn't it.

The known workaround is to create one class by instance :(

     ...
     byte[] classBytes = getClassBytes();
     for (int i = 0; i < 100; i++) {
       Class<?> testClass = acl.loadClass(classBytes);
       try {
         testClass.newInstance();
       }
     ...

Rémi

>
>>
>> class LoadingTest {
>>
>> public void testLoading() {
>> AnonymousClassLoader acl = new AnonymousClassLoader();
>>
>> Class<?> testClass = acl.loadClass(getClassBytes());
>>
>> for (int i = 0; i < 100; i++) {
>> try {
>> testClass.newInstance();
>> }
>> catch(Throwable e) {
>> System.out.println("failed at " + i);
>> e.printStackTrace();
>> throw e;
>> }
>> }
>>    }
>>
>>    private byte[] getClassBytes() {
>> ClassWriter cw = new ClassWriter(0);
>> MethodVisitor mv;
>>
>> cw.visit(V1_7, ACC_PUBLIC + ACC_SUPER, "InstanceTest", null,
>> "java/lang/Object", null);
>> mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
>> mv.visitCode();
>> Label l0 = new Label();
>> mv.visitLabel(l0);
>> mv.visitVarInsn(ALOAD, 0);
>> mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
>> mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out",
>> "Ljava/io/PrintStream;");
>> mv.visitLdcInsn("constructed");
>> mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",
>> "(Ljava/lang/String;)V");
>> mv.visitInsn(RETURN);
>> Label l1 = new Label();
>> mv.visitLabel(l1);
>> mv
>> .visitLocalVariable("this",
>> "Ltest/com/gs/s4j/misc/AnonymousClassLoading;", null,
>> l0, l1, 0);
>> mv.visitMaxs(2, 1);
>> mv.visitEnd();
>> cw.visitEnd();
>> return cw.toByteArray():
>>   }
>> }
>>
>> It appears at the 16th time, the JVM generate a ConstructorAccessor 
>> and it does not know how to handle anonymous class.
>>
>> Thanks,
>> Wei
>>
>> Here is the output from the code.
>> ====================================================================================================================
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> constructed
>> failed at 16
>> java.lang.NoClassDefFoundError: InstanceTest/7572081
>> at sun.reflect.GeneratedConstructorAccessor3.newInstance(Unknown Source)
>> at 
>> sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
>> at java.lang.reflect.Constructor.newInstance(Constructor.java:539)
>> at java.lang.Class.newInstance0(Class.java:372)
>> at java.lang.Class.newInstance(Class.java:325)
>> at 
>> test.com.gs.s4j.misc.AnonymousClassLoading.testLoading(AnonymousClassLoading.java:47)
>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> at 
>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>> at 
>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>> at java.lang.reflect.Method.invoke(Method.java:623)
>> at junit.framework.TestCase.runTest(TestCase.java:164)
>> at junit.framework.TestCase.runBare(TestCase.java:130)
>> at junit.framework.TestResult$1.protect(TestResult.java:106)
>> at junit.framework.TestResult.runProtected(TestResult.java:124)
>> at junit.framework.TestResult.run(TestResult.java:109)
>> at junit.framework.TestCase.run(TestCase.java:120)
>> at 
>> org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
>> at 
>> org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
>> at 
>> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
>> at 
>> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
>> at 
>> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
>> at 
>> org.eclipse.pde.internal.junit.runtime.RemotePluginTestRunner.main(RemotePluginTestRunner.java:62)
>> at 
>> org.eclipse.pde.internal.junit.runtime.CoreTestApplication.run(CoreTestApplication.java:23)
>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> at 
>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>> at 
>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>> at java.lang.reflect.Method.invoke(Method.java:623)
>> at 
>> org.eclipse.equinox.internal.app.EclipseAppContainer.callMethodWithException(EclipseAppContainer.java:574)
>> at 
>> org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
>> at 
>> org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
>> at 
>> org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
>> at 
>> org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
>> at 
>> org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> at 
>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>> at 
>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>> at java.lang.reflect.Method.invoke(Method.java:623)
>> at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
>> at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
>> at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
>> at org.eclipse.equinox.launcher.Main.main(Main.java:1287)
>> Caused by: java.lang.ClassNotFoundException: InstanceTest.7572081
>> at 
>> org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:494)
>> at 
>> org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410)
>> at 
>> org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:398)
>> at 
>> org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:105)
>> at java.lang.ClassLoader.loadClass(ClassLoader.java:331)
>> ... 41 more
>>
>>
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>>
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