mosgi/jmx.agent/src/main/java/org/apache/felix/mosgi/jmx/agent/mx4j/server/interceptor/MBeanServerInterceptorConfigurator.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.apache.felix.mosgi.jmx.agent.mx4j.server.interceptor;

import java.util.ArrayList;

import javax.management.MBeanException;
import javax.management.MBeanServer;
import javax.management.ObjectName;

import org.apache.felix.mosgi.jmx.agent.mx4j.ImplementationException;

/**
 * MBean that configures the MBeanServer --> MBean interceptor chain.
 *
 * @author <a href="mailto:biorn_steedom@users.sourceforge.net">Simone Bordet</a>
 * @version $Revision: 1.1.1.1 $
 */
public class MBeanServerInterceptorConfigurator implements MBeanServerInterceptorConfiguratorMBean
{
	public static final String OBJECT_NAME = "JMImplementation:type=MBeanServerInterceptorConfigurator";

	private final MBeanServer server;
	private final ArrayList preInterceptors = new ArrayList();
	private final ArrayList postInterceptors = new ArrayList();
	private final ArrayList clientInterceptors = new ArrayList();
	private volatile boolean running;
   private boolean chainModified;
   private MBeanServerInterceptor head;

   /**
	 * Creates an instance of this configurator, for the given MBeanServer
	 */
	public MBeanServerInterceptorConfigurator(MBeanServer server)
	{
		this.server = server;
      chainModified = true;
	}

	/**
	 * Appends the given interceptor, provided by the client, to the existing interceptor chain.
	 * @see #registerInterceptor
	 */
	public void addInterceptor(MBeanServerInterceptor interceptor)
	{
		synchronized (clientInterceptors)
		{
			clientInterceptors.add(interceptor);
         chainModified = true;
		}
	}

	/**
	 * Appends the given interceptor, provided by the client, to the existing interceptor chain and registers it as MBean.
	 * @see #addInterceptor
	 */
	public void registerInterceptor(MBeanServerInterceptor interceptor, ObjectName name) throws MBeanException
	{
		// First, try register this interceptor. The call will use the old interceptor chain
		try
		{
			server.registerMBean(interceptor, name);
         addInterceptor(interceptor);
		}
		catch (Exception x)
		{
			throw new MBeanException(x, "Could not register interceptor with name " + name);
		}
	}

	/**
	 * Removes all the interceptors added via {@link #addInterceptor(MBeanServerInterceptor interceptor)}.
	 * @see #addInterceptor
	 */
	public void clearInterceptors()
	{
		synchronized (clientInterceptors)
		{
			clientInterceptors.clear();
         chainModified = true;
		}
	}

	/**
	 * Adds the given interceptor at the beginning of the interceptor chain, before the custom interceptors that may be added
	 * via {@link #addInterceptor}.
	 * This method is called by the MBeanServer during initialization, to configure the interceptors needed to work properly.
	 */
	public void addPreInterceptor(MBeanServerInterceptor interceptor)
	{
		if (isRunning()) throw new ImplementationException();
      preInterceptors.add(interceptor);
	}

	/**
	 * Adds the given interceptor at the end of the interceptor chain, after the custom interceptors that may be added
	 * via {@link #addInterceptor}.
	 * This method is called by the MBeanServer during initialization, to configure the interceptors needed to work properly.
	 */
	public void addPostInterceptor(MBeanServerInterceptor interceptor)
	{
      if (isRunning()) throw new ImplementationException();
      postInterceptors.add(interceptor);
	}

	/**
	 * Returns the head interceptor of the interceptor chain.
	 * The head interceptor is always present.
	 */
	public MBeanServerInterceptor getHeadInterceptor()
	{
		if (!isRunning()) return null;

      if (chainModified) setupChain();

      return head;
	}

   private void setupChain()
   {
      chainModified = false;

      int size = clientInterceptors.size();
      ArrayList chain = new ArrayList(preInterceptors.size() + size + postInterceptors.size());
      chain.addAll(preInterceptors);
      if (size > 0)
      {
         synchronized (clientInterceptors)
         {
            chain.addAll(clientInterceptors);
         }
      }
      chain.addAll(postInterceptors);

      // Set the chain on the first interceptor
      MBeanServerInterceptor first = (MBeanServerInterceptor)chain.get(0);
      first.setChain(chain);

      head = first;
   }

	/**
	 * Starts this configurator, so that the MBeanServer is now able to accept incoming calls.
	 * @see #stop
	 * @see #isRunning
	 */
	public void start()
	{
		if (!isRunning())
		{
			running = true;
		}
	}

	/**
	 * Stops this configurator, so that the MBeanServer is not able to accept incoming calls.
	 * @see #start
	 */
	public void stop()
	{
		if (isRunning())
		{
			running = false;
		}
	}

	/**
	 * Returns whether this configurator is running and thus if the MBeanServer can accept incoming calls
	 * @see #start
	 */
	public boolean isRunning()
	{
		return running;
	}
}