Copyright (c) 2009, 2010 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2009, 2010 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.osgi.service.debug;

import java.util.EventListener;

A debug options listener is notified whenever one of its plug-in option-path entries is changed. A listener is registered as an OSGi service using the DebugOptions.LISTENER_SYMBOLICNAME service property to specify the symbolic name of the debug options listener. 
 The optionsChanged(DebugOptions) method will automatically be called upon registration of the debug options listener service. This allows the listener to obtain the initial debug options. This initial call to the listener will happen even if debug is not enabled at the time of registration (DebugOptions.isDebugEnabled() will return false in this case). 
A debug options listener allows a bundle to cache trace option values in boolean fields for performance
and code cleanliness. For example:
public class Activator implements BundleActivator, DebugOptionsListener {
	public static boolean DEBUG = false;
	public static DebugTrace trace;
	
	public void start(BundleContext context) {
		Hashtable props = new Hashtable(4);
		props.put(DebugOptions.LISTENER_SYMBOLICNAME, "com.mycompany.mybundle");
		context.registerService(DebugOptionsListener.class.getName(), this, props);
	}
	public void optionsChanged(DebugOptions options) {
		if (trace == null)
			trace = options.newDebugTrace("com.mycompany.mybundle");
		DEBUG = options.getBooleanOption("com.mycompany.mybundle/debug", false);
	}
	
	public void doSomeWork() {
		if (DEBUG)
			trace.trace(null, "Doing some work");
	}
	...
} 

Since:
3.5/**
 * A debug options listener is notified whenever one of its plug-in option-path entries is 
 * changed.  A listener is registered as an OSGi service using the {@link DebugOptions#LISTENER_SYMBOLICNAME}
 * service property to specify the symbolic name of the debug options listener.
 * <p>
 * The {@link DebugOptionsListener#optionsChanged(DebugOptions)} method will automatically 
 * be called upon registration of the debug options listener service.  This allows the 
 * listener to obtain the initial debug options.  This initial call to the listener 
 * will happen even if debug is not enabled at the time of registration 
 * ({@link DebugOptions#isDebugEnabled()} will return false in this case).
 * </p>
 * A debug options listener allows a bundle to cache trace option values in boolean fields for performance
 * and code cleanliness. For example:
 * <pre>
 * public class Activator implements BundleActivator, DebugOptionsListener {
 * 	public static boolean DEBUG = false;
 * 	public static DebugTrace trace;
 * 	
 * 	public void start(BundleContext context) {
 * 		Hashtable props = new Hashtable(4);
 * 		props.put(DebugOptions.LISTENER_SYMBOLICNAME, "com.mycompany.mybundle");
 * 		context.registerService(DebugOptionsListener.class.getName(), this, props);
 * 	}
 * 
 * 	public void optionsChanged(DebugOptions options) {
 * 		if (trace == null)
 * 			trace = options.newDebugTrace("com.mycompany.mybundle");
 * 		DEBUG = options.getBooleanOption("com.mycompany.mybundle/debug", false);
 * 	}
 * 	
 * 	public void doSomeWork() {
 * 		if (DEBUG)
 * 			trace.trace(null, "Doing some work");
 * 	}
 * 	...
 * } 
 * </pre>
 * @since 3.5
 */
public interface DebugOptionsListener extends EventListener {

	
Notifies this listener that an option-path for its plug-in has changed.
This method is also called initially by the DebugOptions implementation 
when the listener is registered as a service.  This allows the listener
to obtain the initial set of debug options without the need to 
acquire the debug options service.
Params:
options – a reference to the DebugOptions/**
	 * Notifies this listener that an option-path for its plug-in has changed.
	 * This method is also called initially by the DebugOptions implementation 
	 * when the listener is registered as a service.  This allows the listener
	 * to obtain the initial set of debug options without the need to 
	 * acquire the debug options service.
	 * @param options a reference to the DebugOptions
	 */
	public void optionsChanged(DebugOptions options);
}