Trying to change value of static final field

Hi,

I'm trying to change the value of a static final field in a class using a java
agent that uses ASM.

In the code being changed, if I access the field using reflection then the
value has changed, but if I access the field using the variable name then it
still has the old value.

An example of some output where I've changed the value of a static final String
is as follows:

Value of the static field is: Initial value for static field
Accessed via reflection, field name is: str With Value: Modified value for
static field

Am I doing something wrong when I'm trying to change the field value? Here are
some code samples to show what I'm doing.

The class that is being modified is as follows:

package test.javaagent;

import java.lang.reflect.Field;

import org.junit.Test;

import junit.framework.TestCase;

public class ClassWithStaticField extends TestCase {
	private final static String str = "Initial value for static field";

	@Test
	public void test() throws IllegalArgumentException,
IllegalAccessException {
		ClassWithStaticField.printValue();
	}

	public static void printValue() throws IllegalArgumentException,
			IllegalAccessException {
		System.out.println("Value of the static field is: " + str);

		Field[] fields =
ClassWithStaticField.class.getDeclaredFields();
		for (Field f : fields) {
			System.out.println("Accessed via reflection, field name
is: " + f.getName()
					+ " With Value: " +
f.get(ClassWithStaticField.class));
		}
	}
}



The classes making up the Java Agent and Class Adapters etc:

package test.javaagent;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;

import org.objectweb.asm.ClassAdapter;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.FieldVisitor;

/*
 * Java Agent entry
 */
public class ModifyFieldExample {
	public static void premain(String agentArgs, Instrumentation inst) {
		inst.addTransformer(new MyClassTransformer());
	}
}

class MyClassTransformer implements ClassFileTransformer {

	public byte[] transform(ClassLoader arg0, String arg1, Class<?> arg2,
			ProtectionDomain arg3, byte[] arg4)
			throws IllegalClassFormatException {
		if (arg1.endsWith("ClassWithStaticField")) {
			byte[] transformClass = arg4.clone();
			ClassReader cr = new ClassReader(transformClass);
			ClassWriter cw = new ClassWriter(cr, 0);

			MyClassAdapter ca = new MyClassAdapter(cw);

			cr.accept(ca, 0);

			byte[] transformedBytes = cw.toByteArray();
			return transformedBytes;
		}
		return null;
	}

}

class MyClassAdapter extends ClassAdapter {

	public MyClassAdapter(ClassVisitor arg0) {
		super(arg0);
	}

	@Override
	public FieldVisitor visitField(int arg0, String arg1, String arg2,
			String arg3, Object arg4) {
		if (arg4.equals("Initial value for static field")) {
			return cv.visitField(arg0, arg1, arg2, arg3,
					"Modified value for static field");
		}
		return cv.visitField(arg0, arg1, arg2, arg3, arg4);
	}

}

Thanks in advance.

Cristy

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