I have a project (https://github.com/zhihan/janala2-gradle) that uses java-agent for online instrumentation. I tried to have an annotation class for runtime reflection. The program crashes with NoClassDefFoundError
Exception in thread "main" java.lang.NoClassDefFoundError: janala/logger/DJVM
at com.sun.proxy.$Proxy0.<clinit>(Unknown Source)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:739)
at sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:305)
at sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:303)
at java.security.AccessController.doPrivileged(Native Method)
at sun.reflect.annotation.AnnotationParser.annotationForMap(AnnotationParser.java:303)
at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:293)
at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
at sun.reflect.annotation.AnnotationParser.parseSelectAnnotations(AnnotationParser.java:101)
at sun.reflect.annotation.AnnotationType.<init>(AnnotationType.java:139)
at sun.reflect.annotation.AnnotationType.getInstance(AnnotationType.java:85)
at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:266)
at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72)
at java.lang.reflect.Executable.declaredAnnotations(Executable.java:546)
at java.lang.reflect.Executable.getAnnotation(Executable.java:520)
at java.lang.reflect.Method.getAnnotation(Method.java:607)
at janala.utils.ClassRunner.run(ClassRunner.java:20)
at janala.utils.ClassRunner.main(ClassRunner.java:33)
The call site of the error is simply
Test annotation = method.getAnnotation(Test.class);
If I change the program to first instrument the class, write the instrumented class to a .class file and then run the program with the same classpath. Then it runs fine.
The annotation is declared as
public class Annotations {
/**
* A CATG test.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Test {}
}
And the use of the annotation is like
@Test
public void testAnd() {
Well, it turns out that the reason is in the stack trace
at com.sun.proxy.$Proxy0.<clinit>(Unknown Source)
The proxy class is automatically generated by the JVM as part of the reflection support. And the instrumenter by default will instrument everything. Filtering this package solves the problem.