bundles/org.eclipse.wst.sse.core/src/org/eclipse/wst/sse/core/internal/util/AbstractMemoryListener.java - sourceediting/webtools.sourceediting - Git at Google

 /*******************************************************************************
  * Copyright (c) 2009 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *
  *******************************************************************************/
 package org.eclipse.wst.sse.core.internal.util;

 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Hashtable;
 import java.util.List;

 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.wst.sse.core.internal.Logger;
 import org.eclipse.wst.sse.core.internal.SSECorePlugin;
 import org.osgi.framework.Bundle;
 import org.osgi.framework.BundleContext;
 import org.osgi.framework.BundleException;
 import org.osgi.framework.ServiceRegistration;
 import org.osgi.service.event.Event;
 import org.osgi.service.event.EventAdmin;
 import org.osgi.service.event.EventConstants;
 import org.osgi.service.event.EventHandler;

 /**
  * This responds to memory events.
  *
  * Create an instance of a child of this class with the events you are interested in.
  * Then call connect() to start listening. To stop listening call disconnect();
  */
 public abstract class AbstractMemoryListener implements EventHandler {
 	/**
 	 * The event that indicates that memory is running low at the lowest severity.
 	 * Listeners are requested to release caches that can easily be recomputed.
 	 * The Java VM is not seriously in trouble, but process size is getting higher than
 	 * is deemed acceptable.
 	 */
 	public static final String SEV_NORMAL = "org/eclipse/equinox/events/MemoryEvent/NORMAL"; //$NON-NLS-1$

 	/**
 	 * The event that indicates that memory is running low at medium severity.
 	 * Listeners are requested to release intermediate build results, complex models, etc.
 	 * Memory is getting low and may cause operating system level stress, such as swapping.
 	 */
 	public static final String SEV_SERIOUS = "org/eclipse/equinox/events/MemoryEvent/SERIOUS"; //$NON-NLS-1$

 	/**
 	 * The event that indicates that memory is running low at highest severity.
 	 * Listeners are requested to do things like close editors and perspectives, close database connections, etc.
 	 * Restoring these resources and caches constitutes lots of work, but memory is so low that
 	 * drastic measures are required.
 	 */
 	public static final String SEV_CRITICAL = "org/eclipse/equinox/events/MemoryEvent/CRITICAL"; //$NON-NLS-1$

 	/**
 	 * All of the valid memory severities
 	 */
 	public static final String[] SEV_ALL = { SEV_NORMAL, SEV_SERIOUS, SEV_CRITICAL };

 	/**
 	 * Used to register the {@link EventAdmin} listener
 	 */
 	private static BundleContext CONTEXT =
 		(SSECorePlugin.getDefault() != null) ?
 				SSECorePlugin.getDefault().getBundle().getBundleContext() : null;

 	/**
 	 * the severities that will be reacted to
 	 */
 	private final List fSeverities;

 	/**
 	 * service used to register this listener
 	 */
 	private ServiceRegistration fRegisterService;

 	/**
 	 * Will listen to all memory events
 	 */
 	public AbstractMemoryListener() {
 		this(AbstractMemoryListener.SEV_ALL);
 	}

 	/**
 	 * Will listen to memory events of the given <code>severity</code>
 	 *
 	 * @param severity listen for memory events of this severity
 	 */
 	public AbstractMemoryListener(String severity) {
 		Assert.isNotNull(severity, "Severity can not be null"); //$NON-NLS-1$

 		List severities = new ArrayList(1);
 		severities.add(severity);
 		fSeverities = severities;
 	}

 	/**
 	 * Will listen to memory events of the given <code>severities</code>
 	 *
 	 * @param severities listen for memory events for any of these severities
 	 */
 	public AbstractMemoryListener(String[] severities) {
 		Assert.isNotNull(severities, "Severities can not be null"); //$NON-NLS-1$
 		Assert.isLegal(severities.length > 0, "Severities must specify at least one severity"); //$NON-NLS-1$

 		fSeverities = Arrays.asList(severities);
 	}

 	/**
 	 * Will listen to memory events of the given <code>severities</code>
 	 *
 	 * @param severities listen for memory events for any of these severities
 	 */
 	public AbstractMemoryListener(List severities) {
 		Assert.isNotNull(severities, "Severities can not be null"); //$NON-NLS-1$
 		Assert.isLegal(!severities.isEmpty(), "Severities must specify at least one severity"); //$NON-NLS-1$
 		fSeverities = severities;
 	}

 	/**
 	 * Connect this listener to the {@link EventAdmin}
 	 */
 	public final void connect() {
 		if (CONTEXT != null) {
 			// NOTE: This is TEMPORARY CODE needed to load the plugin
 			// until its done automatically by the product
 			// TODO: Remove me
 			Bundle b = Platform.getBundle("org.eclipse.equinox.event"); //$NON-NLS-1$
 			if (b != null && b.getState() == Bundle.RESOLVED) {
 				try {
 					b.start(Bundle.START_TRANSIENT);
 				}
 				catch (BundleException e) {
 					e.printStackTrace();
 				}
 			}
 			// end remove me

 			//register this handler
 			String[] severities = (String[])fSeverities.toArray(new String[fSeverities.size()]);
 			Hashtable prop = new Hashtable(1);
 			prop.put(EventConstants.EVENT_TOPIC, severities);
 			fRegisterService = CONTEXT.registerService(EventHandler.class.getName(), this, prop);

 			//call any implementer specific connect code
 			doConnect();
 		} else {
 			Logger.log(Logger.WARNING, "Error accessing bundle context. Is Platform running? Not tracking memory events. "); //$NON-NLS-1$
 		}
 	}

 	/**
 	 * Disconnect this listener to the {@link EventAdmin}
 	 */
 	public final void disconnect() {
 		if (fRegisterService != null) {
 			fRegisterService.unregister();
 			fRegisterService = null;
 		}

 		//call any implementer specific disconnect code
 		doDisconnect();
 	}

 	/**
 	 * <p>Filter out any events that are not of the type that this listener handles</p>
 	 *
 	 * @see org.osgi.service.event.EventHandler#handleEvent(org.osgi.service.event.Event)
 	 */
 	public final void handleEvent(Event event) {
 		if (fSeverities.contains(event.getTopic())) {
 			handleMemoryEvent(event);
 		}
 	}

 	/**
 	 * Implementing child classes may assume that only {@link Event}s of the types
 	 * given to the constructor will be given to this method.
 	 *
 	 * @param event the {@link Event} with a topic equal to one of the memory
 	 * severities that this listener is listening for
 	 */
 	protected abstract void handleMemoryEvent(Event event);

 	/**
 	 * Implementers may overrun this method to do setup after connection of this listener
 	 */
 	protected void doConnect() {
 		//do nothing by default
 	}

 	/**
 	 * Implementers may overrun this method to do tear down after disconnection of this listener
 	 */
 	protected void doDisconnect() {
 		//do nothing by default
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2009 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*
	*******************************************************************************/
	package org.eclipse.wst.sse.core.internal.util;

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Hashtable;
	import java.util.List;

	import org.eclipse.core.runtime.Assert;
	import org.eclipse.core.runtime.Platform;
	import org.eclipse.wst.sse.core.internal.Logger;
	import org.eclipse.wst.sse.core.internal.SSECorePlugin;
	import org.osgi.framework.Bundle;
	import org.osgi.framework.BundleContext;
	import org.osgi.framework.BundleException;
	import org.osgi.framework.ServiceRegistration;
	import org.osgi.service.event.Event;
	import org.osgi.service.event.EventAdmin;
	import org.osgi.service.event.EventConstants;
	import org.osgi.service.event.EventHandler;

	/**
	* This responds to memory events.
	*
	* Create an instance of a child of this class with the events you are interested in.
	* Then call connect() to start listening. To stop listening call disconnect();
	*/
	public abstract class AbstractMemoryListener implements EventHandler {
	/**
	* The event that indicates that memory is running low at the lowest severity.
	* Listeners are requested to release caches that can easily be recomputed.
	* The Java VM is not seriously in trouble, but process size is getting higher than
	* is deemed acceptable.
	*/
	public static final String SEV_NORMAL = "org/eclipse/equinox/events/MemoryEvent/NORMAL"; //$NON-NLS-1$

	/**
	* The event that indicates that memory is running low at medium severity.
	* Listeners are requested to release intermediate build results, complex models, etc.
	* Memory is getting low and may cause operating system level stress, such as swapping.
	*/
	public static final String SEV_SERIOUS = "org/eclipse/equinox/events/MemoryEvent/SERIOUS"; //$NON-NLS-1$

	/**
	* The event that indicates that memory is running low at highest severity.
	* Listeners are requested to do things like close editors and perspectives, close database connections, etc.
	* Restoring these resources and caches constitutes lots of work, but memory is so low that
	* drastic measures are required.
	*/
	public static final String SEV_CRITICAL = "org/eclipse/equinox/events/MemoryEvent/CRITICAL"; //$NON-NLS-1$

	/**
	* All of the valid memory severities
	*/
	public static final String[] SEV_ALL = { SEV_NORMAL, SEV_SERIOUS, SEV_CRITICAL };

	/**
	* Used to register the {@link EventAdmin} listener
	*/
	private static BundleContext CONTEXT =
	(SSECorePlugin.getDefault() != null) ?
	SSECorePlugin.getDefault().getBundle().getBundleContext() : null;

	/**
	* the severities that will be reacted to
	*/
	private final List fSeverities;

	/**
	* service used to register this listener
	*/
	private ServiceRegistration fRegisterService;

	/**
	* Will listen to all memory events
	*/
	public AbstractMemoryListener() {
	this(AbstractMemoryListener.SEV_ALL);
	}

	/**
	* Will listen to memory events of the given <code>severity</code>
	*
	* @param severity listen for memory events of this severity
	*/
	public AbstractMemoryListener(String severity) {
	Assert.isNotNull(severity, "Severity can not be null"); //$NON-NLS-1$

	List severities = new ArrayList(1);
	severities.add(severity);
	fSeverities = severities;
	}

	/**
	* Will listen to memory events of the given <code>severities</code>
	*
	* @param severities listen for memory events for any of these severities
	*/
	public AbstractMemoryListener(String[] severities) {
	Assert.isNotNull(severities, "Severities can not be null"); //$NON-NLS-1$
	Assert.isLegal(severities.length > 0, "Severities must specify at least one severity"); //$NON-NLS-1$

	fSeverities = Arrays.asList(severities);
	}

	/**
	* Will listen to memory events of the given <code>severities</code>
	*
	* @param severities listen for memory events for any of these severities
	*/
	public AbstractMemoryListener(List severities) {
	Assert.isNotNull(severities, "Severities can not be null"); //$NON-NLS-1$
	Assert.isLegal(!severities.isEmpty(), "Severities must specify at least one severity"); //$NON-NLS-1$
	fSeverities = severities;
	}

	/**
	* Connect this listener to the {@link EventAdmin}
	*/
	public final void connect() {
	if (CONTEXT != null) {
	// NOTE: This is TEMPORARY CODE needed to load the plugin
	// until its done automatically by the product
	// TODO: Remove me
	Bundle b = Platform.getBundle("org.eclipse.equinox.event"); //$NON-NLS-1$
	if (b != null && b.getState() == Bundle.RESOLVED) {
	try {
	b.start(Bundle.START_TRANSIENT);
	}
	catch (BundleException e) {
	e.printStackTrace();
	}
	}
	// end remove me

	//register this handler
	String[] severities = (String[])fSeverities.toArray(new String[fSeverities.size()]);
	Hashtable prop = new Hashtable(1);
	prop.put(EventConstants.EVENT_TOPIC, severities);
	fRegisterService = CONTEXT.registerService(EventHandler.class.getName(), this, prop);

	//call any implementer specific connect code
	doConnect();
	} else {
	Logger.log(Logger.WARNING, "Error accessing bundle context. Is Platform running? Not tracking memory events. "); //$NON-NLS-1$
	}
	}

	/**
	* Disconnect this listener to the {@link EventAdmin}
	*/
	public final void disconnect() {
	if (fRegisterService != null) {
	fRegisterService.unregister();
	fRegisterService = null;
	}

	//call any implementer specific disconnect code
	doDisconnect();
	}

	/**
	* <p>Filter out any events that are not of the type that this listener handles</p>
	*
	* @see org.osgi.service.event.EventHandler#handleEvent(org.osgi.service.event.Event)
	*/
	public final void handleEvent(Event event) {
	if (fSeverities.contains(event.getTopic())) {
	handleMemoryEvent(event);
	}
	}

	/**
	* Implementing child classes may assume that only {@link Event}s of the types
	* given to the constructor will be given to this method.
	*
	* @param event the {@link Event} with a topic equal to one of the memory
	* severities that this listener is listening for
	*/
	protected abstract void handleMemoryEvent(Event event);

	/**
	* Implementers may overrun this method to do setup after connection of this listener
	*/
	protected void doConnect() {
	//do nothing by default
	}

	/**
	* Implementers may overrun this method to do tear down after disconnection of this listener
	*/
	protected void doDisconnect() {
	//do nothing by default
	}
	}