com.google.monitoring.runtime.instrumentation

Class ConstructorInstrumenter

java.lang.Object

com.google.monitoring.runtime.instrumentation.ConstructorInstrumenter

All Implemented Interfaces:

ClassFileTransformer

public class ConstructorInstrumenter
extends Object
implements ClassFileTransformer

Instruments bytecode by inserting a specified call in the constructor of a given class. This class is intended to be loaded by a javaagent; end-users will want to add ConstructorCallbacks by invoking instrumentClass(Class, ConstructorCallback).

Author:

Jeremy Manson

Method Summary

Modifier and Type	Method and Description
static byte[]	instrument(byte[] originalBytes, Class<?> classBeingRedefined) Given the bytes representing a class, add invocations of the ConstructorCallback method to the constructor.
static void	instrumentClass(Class<?> c, ConstructorCallback<?> sampler) Ensures that the given sampler will be invoked every time a constructor for class c is invoked.
static void	invokeSamplers(Object o) Bytecode is rewritten to invoke this method; it calls the sampler for the given class.
byte[]	transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

instrumentClass

public static void instrumentClass(Class<?> c,
                                   ConstructorCallback<?> sampler)
                            throws UnmodifiableClassException

Ensures that the given sampler will be invoked every time a constructor for class c is invoked.

Parameters:

c - The class to be tracked

sampler - the code to be invoked when an instance of c is constructed

Throws:

UnmodifiableClassException - if c cannot be modified.

transform

public byte[] transform(ClassLoader loader,
                        String className,
                        Class<?> classBeingRedefined,
                        ProtectionDomain protectionDomain,
                        byte[] classfileBuffer)

Specified by:

transform in interface ClassFileTransformer

instrument

public static byte[] instrument(byte[] originalBytes,
                                Class<?> classBeingRedefined)

Given the bytes representing a class, add invocations of the ConstructorCallback method to the constructor.

Parameters:

originalBytes - the original byte[] code.

classBeingRedefined - the class being redefined.

Returns:

the instrumented byte[] code.

invokeSamplers

public static void invokeSamplers(Object o)

Bytecode is rewritten to invoke this method; it calls the sampler for the given class. Note that, unless the javaagent command line argument "subclassesAlso" is specified, it won't do anything if o is a subclass of the class that was supposed to be tracked.

Parameters:

o - the object passed to the samplers.