java.lang.instrument

Interface ClassFileTransformer

public interface ClassFileTransformer

This interface should be implemented by classes wishing to transform classes bytecode when defining or redefining classes.

Since:

1.5

See Also:

Instrumentation, Instrumentation.addTransformer(java.lang.instrument.ClassFileTransformer), Instrumentation.removeTransformer(java.lang.instrument.ClassFileTransformer)

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	transform(java.lang.ClassLoader loader, java.lang.String className, java.lang.Class<?> classBeingRedefined, java.security.ProtectionDomain protectionDomain, byte[] classfileBuffer) Implementation of this method transforms a class by redefining its bytecodes.

Method Detail

transform

byte[] transform(java.lang.ClassLoader loader,
               java.lang.String className,
               java.lang.Class<?> classBeingRedefined,
               java.security.ProtectionDomain protectionDomain,
               byte[] classfileBuffer)
                 throws IllegalClassFormatException

Implementation of this method transforms a class by redefining its bytecodes. Once a ClassFileTransformer object registers itself to the Instrumentation object, this method will be called each time a class is defined (ClassLoader.defineClass) or redefined (Instrumentation.redefineClasses)

Parameters:

loader - the loader of the class

className - the name of the class with packages separated with "/"

classBeingRedefined - the class being redefined if it's the case, null otherwise

protectionDomain - the protection domain of the class being defined or redefined

classfileBuffer - the input byte buffer in class file format

Returns:

a class file buffer or null when no transformation has been performed

Throws:

IllegalClassFormatException - if the byte buffer does not represent a well-formed class file

See Also:

Instrumentation.redefineClasses(java.lang.instrument.ClassDefinition[])