com.develorium.metracer.dynamic.MetracerClassFileTransformer.java Source code

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Here is the source code for com.develorium.metracer.dynamic.MetracerClassFileTransformer.java

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/*
 * Copyright 2015-2016 Michael Kocherov
 *
 * 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 com.develorium.metracer.dynamic;

import java.lang.instrument.*;
import java.security.ProtectionDomain;
import java.util.*;
import java.util.regex.*;
import java.io.*;
import org.objectweb.asm.*;
import org.objectweb.asm.tree.*;
import com.develorium.metracer.*;
import com.develorium.metracer.asm.*;

public class MetracerClassFileTransformer implements ClassFileTransformer {
    private Agent agent = null;

    MetracerClassFileTransformer(Agent theAgent) {
        agent = theAgent;
    }

    @Override
    public byte[] transform(ClassLoader theLoader, String theClassName, Class<?> theClassBeingRedefined,
            ProtectionDomain theProtectionDomain, byte[] theClassfileBuffer) throws IllegalClassFormatException {
        Patterns patterns = agent.getPatterns();

        try {
            if (patterns == null)
                return theClassfileBuffer;

            InstrumentClassResult icr = instrumentClass(theClassfileBuffer,
                    theLoader != null ? theLoader : getClass().getClassLoader(), patterns);

            if (icr.isChanged) {
                String classLoaderName = theLoader != null ? theLoader.toString() : "<boostrap>";
                String message = String.format("%s (class loader %s) was instrumented (%s, %s)", theClassName,
                        classLoaderName, patterns.getClassMatchingPattern(), patterns.getMethodMatchingPattern());
                com.develorium.metracer.Runtime.say(message);
                return icr.bytecode;
            }

            return theClassfileBuffer;
        } catch (Throwable t) {
            StringWriter sw = new StringWriter();
            t.printStackTrace(new PrintWriter(sw));
            com.develorium.metracer.Runtime
                    .say(String.format("Failed to instrument class %s, class loader %s: %s\n%s", theClassName,
                            theLoader, t.toString(), sw.toString()));
        }

        return theClassfileBuffer;
    }

    private static class InstrumentClassResult {
        boolean isChanged = false;
        byte[] bytecode = null;
    }

    private InstrumentClassResult instrumentClass(byte theBytecode[], ClassLoader theLoader, Patterns thePatterns) {
        ClassReader reader = new ClassReader(theBytecode);
        ClassNode parsedClass = new ClassNode();
        reader.accept(parsedClass, 0);

        MetracerClassWriter writer = new MetracerClassWriter(reader, theLoader);
        MetracerClassVisitor visitor = new MetracerClassVisitor(writer, theLoader, thePatterns, parsedClass);
        reader.accept(visitor, ClassReader.EXPAND_FRAMES);

        InstrumentClassResult rv = new InstrumentClassResult();
        rv.isChanged = visitor.getIsChanged();
        rv.bytecode = visitor.getIsChanged() ? writer.toByteArray() : theBytecode;
        return rv;
    }
}