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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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/*******************************************************************************
 * Copyright (c) 2005 Contributors.
 * All rights reserved.
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Public License v 2.0
 * which accompanies this distribution and is available at
 * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.txt
 *
 * Contributors:
 *   Alexandre Vasseur         initial implementation
 *******************************************************************************/
package org.aspectj.weaver.loadtime;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;

/**
 * Java 1.5 preMain agent to hook in the class pre processor
 * Can be used with -javaagent:aspectjweaver.jar
 *
 * @author Alexandre Vasseur
 * @author Alexander Kriegisch
 */
public class Agent {

    /**
     * The instrumentation instance
     */
    private static Instrumentation s_instrumentation;

    /**
     * The ClassFileTransformer wrapping the weaver
     */
    private static ClassFileTransformer s_transformer = new ClassPreProcessorAgentAdapter();

    /**
     * JSR-163 preMain Agent entry method
     *
     * @param options
     * @param instrumentation
     */
    public static void premain(String options, Instrumentation instrumentation) {
    	/* Handle duplicate agents */
    	if (s_instrumentation != null) {
    		return;
    	}
        s_instrumentation = instrumentation;
        s_instrumentation.addTransformer(s_transformer);
    }

    public static void agentmain(String options, Instrumentation instrumentation) {
        premain(options, instrumentation);
    }

    /**
     * Returns the Instrumentation system level instance
     */
    public static Instrumentation getInstrumentation() {
        if (s_instrumentation == null) {
            throw new UnsupportedOperationException(
                "AspectJ weaving agent was neither started via '-javaagent' (preMain) " +
                "nor attached via 'VirtualMachine.loadAgent' (agentMain)");
        }
        return s_instrumentation;
    }

}