使用ProGuard后，InvocationTargetException

Question

I obfuscate my jar with ProGuard using Eclipse Ant script.

I use configuration file almost identical from this answer . I have just added more references to proper libraries using -libraryjars option and omit two warnings using -dontnote

After that I include generated jar into fat jar with those libraries. It works okay if above mentioned .cfg is used.

But not much obfuscation is done. In examples for typical application it is said to use

-keep public class mypackage.MyMain {
    public static void main(java.lang.String[]);
}

So this is changed

-keep public class * {
    public protected *;
}

After regenerating new fat jar it throws Exception:

    Exception in thread "main" java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoa
der.java:58)
Caused by: java.lang.NullPointerException
        at mypackage.a.d.a.a(SourceFile:11)
        at mypackage.a.d.a.a(SourceFile:44)
        at mypackage.MyMain.main(SourceFile:61)
        ... 5 more

How can I fix it? Please, give me some advice how to investigate more on this issue.

Answer 1

I was able to solve this specific problem with inspecting the obfuscated jar with JD Java Decompiler.

In there way a line:

String path = JarEclipse.class.getResource("MyClass.class").toString();

which caused NullPointerException because getResource returns null, because MyClass.class was renamed.