Class is frozen exception while isFrozen returns false about javassist

[chibash]

Hi,

Once you execute CtClass#writeFile(), then the class get frozen because you've already written it out and there is no way to modify that class if the class is loaded onto the JVM.

You can get a CtClass object back to be modifiable again by:

cc.stopPruning(true);    // don't delete the data if it is written out.
    :
cc.writeFile();
cc.defrost();             // now modifiable again

Another approach is to use debugWriteFile() instead of writeFile().
debugWriteFile() keeps a CtClass object modifiable after it is written out.
You don't have to call #stopPruning() or #defrost().

[erdem-aslan]

Hello,

Thanks for responding.

My very first attempt to modify the class is just after the isFrozen method call. So I am not calling writeFile if you check the sample I've provided.

Let me provide some comments on the steps, code is messy I know.

CtClass cc;
            try {
                cc = classPool.get (className); // just getting the class

                getLog().info("Class: " + cc.getSimpleName() + " is frozen ? : " + cc.isFrozen()); // checking if its frozen

            } catch (NotFoundException e) {
                e.printStackTrace ();
                continue;
            }

            if (cc.isAnnotation () // skipping interfaces and annotations
                    || cc.isInterface ())
                continue;

            CtMethod[] methods = cc.getDeclaredMethods (); // getting methods

            for (CtMethod ctMethod : methods) {

                try {

                    ctMethod.addLocalVariable ("executionStarted", CtClass.longType); // Class is frozen exception is thrown right away !
                    ctMethod.insertBefore ("executionStarted = System.currentTimeMillis ();");
                    ctMethod.insertAfter ("{final long executionFinished = System.currentTimeMillis ();"
                            + "System.out.println(\"Execution in ms: \" + (executionFinished-executionStarted));}");

                    cc.writeFile ("."); // The very first time of writeFile method in the whole project

                } catch (Throwable e) {
                    getLog ().error ("Error on class: "
                            + cc.getName ()
                            + " for method: "
                            + ctMethod.getName ());
                    getLog ().error (e);
                }
            }

I event tried calling defrost () before trying anything on the class but no good.

EDIT:

I think I overlooked one case and now I can make sense of the situation.

While iterating over methods I couldn't observe at least one successful iteration without exception thrown, according to your response there has to be at least one good iteration and consequents should all fail.

Maybe getDeclaredMethods returns also the default constructor and I missed it within debugs? I'll check and update here.

Thanks

[erdem-aslan]

Yes, I missed the successful first one while iterating over the methods of the class, simply moving out the cc.writeFile call to the outer loop did the trick.

Thanks again for your response

Cheers