agent/src/main/java/org/mvndaemon/mvnd/agent/Agent.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.mvndaemon.mvnd.agent;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import javassist.ClassPool;
import javassist.CtClass;

public class Agent {

    public static final String START_WITH_PIPES = "if (redirects != null\n"
            + "         && redirects[1] == ProcessBuilder$Redirect.INHERIT\n"
            + "         && redirects[2] == ProcessBuilder$Redirect.INHERIT) {\n"
            + "   redirects[1] = redirects[2] = ProcessBuilder$Redirect.PIPE;"
            + "   Process p = start(redirects);\n"
            + "   AgentHelper.pump(p.getInputStream(), System.out);\n"
            + "   AgentHelper.pump(p.getErrorStream(), System.err);\n"
            + "   return p;\n"
            + "}";

    public static void premain(String args, Instrumentation instrumentation) throws Exception {
        instrumentation.addTransformer(new ClassFileTransformer() {
            @Override
            public byte[] transform(
                    ClassLoader loader,
                    String className,
                    Class<?> classBeingRedefined,
                    ProtectionDomain protectionDomain,
                    byte[] classfileBuffer)
                    throws IllegalClassFormatException {
                if ("java/lang/ProcessBuilder".equals(className)) {
                    try {
                        ClassPool pool = ClassPool.getDefault();
                        CtClass clazz = pool.get("java.lang.ProcessBuilder");
                        pool.importPackage("org.mvndaemon.mvnd.pump");
                        clazz.getDeclaredMethod(
                                        "start",
                                        new CtClass[] {clazz.getClassPool().get("java.lang.ProcessBuilder$Redirect[]")})
                                .insertBefore(START_WITH_PIPES);
                        byte[] data = clazz.toBytecode();
                        clazz.detach();
                        return data;
                    } catch (Throwable e) {
                        System.err.println(e);
                        throw new IllegalClassFormatException(e.toString());
                    }
                } else {
                    return classfileBuffer;
                }
            }
        });
    }
}