/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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.springframework.instrument;

import java.lang.instrument.Instrumentation;

Java agent that saves the Instrumentation interface from the JVM for later use. 
Author:
Rod Johnson, Juergen Hoeller
See Also:
InstrumentationLoadTimeWeaver
Since:
2.0/**
 * Java agent that saves the {@link Instrumentation} interface from the JVM
 * for later use.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 2.0
 * @see org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver
 */
public final class InstrumentationSavingAgent {

	private static volatile Instrumentation instrumentation;


	private InstrumentationSavingAgent() {
	}


	
Save the Instrumentation interface exposed by the JVM. /**
	 * Save the {@link Instrumentation} interface exposed by the JVM.
	 */
	public static void premain(String agentArgs, Instrumentation inst) {
		instrumentation = inst;
	}

	
Save the Instrumentation interface exposed by the JVM. This method is required to dynamically load this Agent with the Attach API. /**
	 * Save the {@link Instrumentation} interface exposed by the JVM.
	 * This method is required to dynamically load this Agent with the Attach API.
	 */
	public static void agentmain(String agentArgs, Instrumentation inst) {
		instrumentation = inst;
	}

	
Return the Instrumentation interface exposed by the JVM. 
Note that this agent class will typically not be available in the classpath unless the agent is actually specified on JVM startup. If you intend to do conditional checking with respect to agent availability, consider using getInstrumentation.getInstrumentation() instead - which will work without the agent class in the classpath as well. 
See Also:
getInstrumentation.getInstrumentation()
Returns:
the Instrumentation instance previously saved when the premain or agentmain methods was called by the JVM; will be null if this class was not used as Java agent when this JVM was started or it wasn't installed as agent using the Attach API./**
	 * Return the {@link Instrumentation} interface exposed by the JVM.
	 * <p>Note that this agent class will typically not be available in the classpath
	 * unless the agent is actually specified on JVM startup. If you intend to do
	 * conditional checking with respect to agent availability, consider using
	 * {@link org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver#getInstrumentation()}
	 * instead - which will work without the agent class in the classpath as well.
	 * @return the {@code Instrumentation} instance previously saved when
	 * the {@link #premain} or {@link #agentmain} methods was called by the JVM;
	 * will be {@code null} if this class was not used as Java agent when this
	 * JVM was started or it wasn't installed as agent using the Attach API.
	 * @see org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver#getInstrumentation()
	 */
	public static Instrumentation getInstrumentation() {
		return instrumentation;
	}

}