Java – Proguard won’t keep a class member’s enums

enumsjavaproguard

I'm working on a library that is distributed as a java jar, and I'm running proguard on it in such a way as to only leave the required interfaces exposed. I have a configuration class with a bunch of member variables and some enum defines. My proguard script preserves the member variables fine, however, the enum definitions are being obfuscated. I've tried everything I can think of to force proguard to retain these internally defined and public enums, but I can't get it to work.

Right now I'm using:

-keep public class com.stuff.MyConfigObject {
    public *;
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

If I try:

-keep public enum com.stuff.MyConfigObject.MyEnum

I get an ambiguous error:
"Note: the configuration refers to the unknown class 'com.stuff.MyConfigObject.MyEnum'"

Thanks for the help!

Best Answer

Try com.stuff.MyConfigObject$MyEnum instead. The Proguard class specification expects $ as the separator for inner classes.

Actually, for what you want maybe the best option is something like this:

-keep public enum com.stuff.MyConfigObject$** {
    **[] $VALUES;
    public *;
}

This will keep only the required members for all enums nested within MyConfigObject - the required members being the $VALUES[] array (see this question for an explanation) and any public members of the enum. Any other members (e.g. private fields methods) will not be kept.

As noted by Jesse and myself in the comments - since you are processing a library, you must also add the -keepAttributes option. From the reference guide:

For example, you should at least keep the Exceptions, InnerClasses, and Signature attributes when processing a library.

Related Solutions

Java – How to test a class that has private methods, fields or inner classes

Update:

Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
foo.privateMethod(x, y, z);
foo.privateField = value;
This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.

If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.

Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final variables through reflection.

Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
return method.invoke(targetObject, argObjects);

And for fields:

Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, value);

Notes:
1. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. The same thing applies for getDeclaredField.
2. The setAccessible(true) is required to play around with privates.

Java inner class and static nested class

From the Java Tutorial:

Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are simply called static nested classes. Non-static nested classes are called inner classes.

Static nested classes are accessed using the enclosing class name:

OuterClass.StaticNestedClass

For example, to create an object for the static nested class, use this syntax:

OuterClass.StaticNestedClass nestedObject = new OuterClass.StaticNestedClass();

Objects that are instances of an inner class exist within an instance of the outer class. Consider the following classes:

class OuterClass {
    ...
    class InnerClass {
        ...
    }
}

An instance of InnerClass can exist only within an instance of OuterClass and has direct access to the methods and fields of its enclosing instance.

To instantiate an inner class, you must first instantiate the outer class. Then, create the inner object within the outer object with this syntax:

OuterClass outerObject = new OuterClass()
OuterClass.InnerClass innerObject = outerObject.new InnerClass();

see: Java Tutorial - Nested Classes

For completeness note that there is also such a thing as an inner class without an enclosing instance:

class A {
  int t() { return 1; }
  static A a =  new A() { int t() { return 2; } };
}

Here, new A() { ... } is an inner class defined in a static context and does not have an enclosing instance.

Best Answer

Related Solutions

Java – How to test a class that has private methods, fields or inner classes

Java inner class and static nested class

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