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Agent.java
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Agent.java
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/*
* Copyright 2014 brutusin.org
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.brutusin.instrumentation;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
public class Agent {
private static int counter;
public static void premain(final String agentArgs, Instrumentation instrumentation) throws InstantiationException {
counter++;
final String callbackId = String.valueOf(counter);
try {
if (agentArgs == null) {
throw new IllegalArgumentException("Agent argument is required of the form 'interceptor-class-name[;interceptor-custom-args]'");
}
String[] tokens = agentArgs.split(";",2);
Class<?> clazz = Agent.class.getClassLoader().loadClass(tokens[0]);
final Interceptor interceptor = (Interceptor) clazz.newInstance();
if(tokens.length==2){
interceptor.init(tokens[1]);
} else {
interceptor.init(null);
}
Callback.registerCallback(callbackId, interceptor);
instrumentation.addTransformer(new ClassFileTransformer() {
public byte[] transform(final ClassLoader loader,
final String className, final Class<?> classBeingRedefined,
final ProtectionDomain protectionDomain,
final byte[] classfileBuffer)
throws IllegalClassFormatException {
if (!isAncestor(Agent.class.getClassLoader(), loader)) {
return classfileBuffer;
}
return AccessController.doPrivileged(new PrivilegedAction<byte[]>() {
public byte[] run() {
Instrumentator instrumentator = new Instrumentator(className, classfileBuffer, interceptor, callbackId);
return instrumentator.modifyClass();
}
});
}
});
} catch (Throwable th) {
th.printStackTrace(System.err);
}
}
private static boolean isAncestor(ClassLoader ancestor, ClassLoader cl) {
if (ancestor == null || cl == null) {
return false;
}
if (ancestor.equals(cl)) {
return true;
}
return isAncestor(ancestor, cl.getParent());
}
}