/**
* Entry point for instrumentation, invoked by the modified classloader for JVM <= 1.4x. For Java
* 1.5 it is invoked by the agent interface of the JVM. Thus this method is invoked for each class
* being loaded by the JVM. This does not imply that all classes are instrumented.
*
* @param loader the class loader attempting to load this class.
* @param className class name of class being loaded
* @param protectionDomain security protection domain
* @param classfileBuffer
* @param offset
* @param length
* @return null if the class is not instrumented (modified)
*/
public static byte[] transform(
ClassLoader loader,
String className,
ProtectionDomain protectionDomain,
byte[] classfileBuffer,
int offset,
int length) {
try {
init();
// Check to see if we already know this class loader or add it to the Javassist ClassPool
// search path if
// it's new. This is important in J2EE- and Servlet containers that have class loader
// hierarchies
if (!classLoaders.containsKey(
loader)) { // <<< TODO: this is a weak hash map, will this really work as intended?
classPool.insertClassPath(new LoaderClassPath(loader));
classLoaders.put(loader, null);
}
// Parses the byte array into a CtClass instance.
CtClass ctc = loadClass(classfileBuffer, offset, length);
// transforms the class if it is of any interest to us.
byte[] bb = findTypeAndTransform(ctc);
// removes the CtClass from the pool to release memory
ctc.detach();
return bb;
} catch (Throwable t) {
Log.warning(
"Exception during categorizeAndTransform of class "
+ className
+ ". The class will be ignored.",
t);
return null;
}
}
private static void init() {
if (!initialized) {
initialized = true;
Log.info("Usemon agent initialized");
}
// Bootstrap the publisher
Registry.ensurePublisherAvailable();
}
private static byte[] findTypeAndTransform(CtClass javaClass)
throws CannotCompileException, IOException, NotFoundException {
int componentType = findComponentType(javaClass);
ClassFile cf = javaClass.getClassFile();
if (componentType != Info.COMPONENT_UNKNOWN && !cf.isInterface() && !cf.isAbstract()) {
Log.info(
javaClass.getName()
+ " is of type "
+ Info.TYPES[componentType]
+ " and will be instrumented");
switch (componentType) {
case Info.COMPONENT_SESSIONBEAN:
return ComponentTransformer.transformSessionBean(javaClass);
case Info.COMPONENT_ENTITYBEAN:
return ComponentTransformer.transformEntityBean(javaClass);
case Info.COMPONENT_MESSAGEDRIVENBEAN:
return ComponentTransformer.transformMessageDrivenBean(javaClass);
case Info.COMPONENT_CUSTOM:
return ComponentTransformer.transformCustom(javaClass);
case Info.COMPONENT_QUEUESENDER:
return ComponentTransformer.transformQueueSender(javaClass);
case Info.COMPONENT_SERVLET:
return ComponentTransformer.transformServlet(javaClass);
case Info.COMPONENT_SINGLETON:
return ComponentTransformer.transformSingleton(javaClass);
case Info.COMPONENT_TOPICPUBLISHER:
return ComponentTransformer.transformTopicPublisher(javaClass);
case Info.COMPONENT_SQLSTATEMENT:
return ComponentTransformer.transformSQLStatement(javaClass);
case Info.COMPONENT_SQLCONNECTION:
return ComponentTransformer.transformSQLConnection(javaClass);
default:
return null;
}
}
return null;
}