org.eclipse.emf.emfstore.common/src/org/eclipse/emf/emfstore/common/observer/ObserverBus.java - emf-store/org.eclipse.emf.emfstore.core - Git at Google

 /*******************************************************************************
  * Copyright 2011 Chair for Applied Software Engineering,
  * Technische Universitaet Muenchen.
  * All rights reserved. This program and the accompanying materials
  * are made available under the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  ******************************************************************************/
 package org.eclipse.emf.emfstore.common.observer;

 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;

 import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionElement;
 import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPoint;
 import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPointException;

 /**
  * This is a universal observer bus. This class follows the publish/subscribe pattern, it is a central dispatcher for
  * observers and makes use of generics in order to allow type safety. It can be used as singleton or be injected through
  * DI.
  * Observers have to implement the {@link IObserver} interface, which is only used as a marker. Future use of
  * Annotations is possible.
  * by using {@link #notify(Class)} (e.g. <code>bus.notify(MyObserver.class).myObserverMethod()</code>) all registered
  * Observers are notified.
  * This is implemented by using the java {@link Proxy} class. By calling {@link #notify(Class)} a proxy is returned,
  * which then calls all registered observers.
  * The proxy can also be casted into {@link ObserverCall}, which allows to access all results by the different
  * observers.
  *
  *
  * Example code:
  *
  * <pre>
  * // A is IObserver
  * A a = new A() {
  *
  * 	public void foo() {
  * 		System.out.println(&quot;A says: go!&quot;);
  * 	}
  * };
  *
  * // B extends A and is IObserver
  * B b = new B() {
  *
  * 	public void say(String ja) {
  * 		System.out.println(&quot;B says: &quot; + ja);
  * 	}
  *
  * 	public void foo() {
  * 		System.out.println(&quot;B says: h??&quot;);
  * 	}
  * };
  *
  * // B is registered first
  * ObserverBus.register(b);
  * ObserverBus.register(a);
  *
  * ObserverBus.notify(A.class).foo();
  *
  * ObserverBus.notify(B.class).say(&quot;w00t&quot;);
  *
  * // Output:
  *
  * // B says: h??
  * // A says: go!
  * //
  * // B says: w00t
  *
  * </pre>
  *
  * @author wesendon
  */
 public class ObserverBus {

 	/**
 	 * Initializes the singleton instance statically.
 	 */
 	private static class SingletonHolder {
 		public static final ObserverBus INSTANCE = new ObserverBus();
 	}

 	/**
 	 * Static ObserverBus singleton. Use of singleton is optional, for that reason the constructor is public.
 	 *
 	 * @return Static instance of the observerbus
 	 */
 	public static ObserverBus getInstance() {
 		return SingletonHolder.INSTANCE;
 	}

 	private HashMap<Class<? extends IObserver>, List<IObserver>> observerMap;

 	/**
 	 * Default constructor.
 	 */
 	public ObserverBus() {
 		observerMap = new HashMap<Class<? extends IObserver>, List<IObserver>>();
 		collectionExtensionPoints();
 	}

 	/**
 	 * This method allows you to notify all observers.
 	 *
 	 * @param <T> class of observer
 	 * @param clazz class of observer
 	 * @return call object
 	 */
 	public <T extends IObserver> T notify(Class<T> clazz) {
 		return (T) notify(clazz, false);
 	}

 	/**
 	 * This method allows you to notify all observers.
 	 *
 	 * @param <T> class of observer
 	 * @param clazz class of observer
 	 * @param prioritized sort observer after {@link PrioritizedIObserver}
 	 *
 	 * @return call object
 	 */
 	public <T extends IObserver> T notify(Class<T> clazz, boolean prioritized) {
 		if (clazz == null) {
 			return null;
 		}
 		return (T) createProxy(clazz, false);
 	}

 	/**
 	 * Registers an observer for all observer interfaces implemented by the object or its super classes.
 	 *
 	 * @param observer observer object
 	 */
 	public void register(IObserver observer) {
 		register(observer, getObserverInterfaces(observer));
 	}

 	/**
 	 * Registers an observer for the specified observer interfaces.
 	 *
 	 * @param observer observer object
 	 * @param classes set of classes
 	 */
 	public void register(IObserver observer, Class<? extends IObserver>... classes) {
 		for (Class<? extends IObserver> iface : classes) {
 			if (iface.isInstance(observer)) {
 				addObserver(observer, iface);
 			}
 		}
 	}

 	/**
 	 * Unregisters an observer for all observer interfaces implemented by the object or its super classes.
 	 *
 	 * @param observer observer object
 	 */
 	public void unregister(IObserver observer) {
 		unregister(observer, getObserverInterfaces(observer));
 	}

 	/**
 	 * Unregisters an observer for the specified observer interfaces.
 	 *
 	 * @param observer observer object
 	 * @param classes set of classes
 	 */
 	public void unregister(IObserver observer, Class<? extends IObserver>... classes) {
 		for (Class<? extends IObserver> iface : classes) {
 			if (iface.isInstance(observer)) {
 				removeObserver(observer, iface);
 			}
 		}
 	}

 	private void addObserver(IObserver observer, Class<? extends IObserver> iface) {
 		List<IObserver> observers = initObserverList(iface);
 		observers.add(observer);
 	}

 	private void removeObserver(IObserver observer, Class<? extends IObserver> iface) {
 		List<IObserver> observers = initObserverList(iface);
 		observers.remove(observer);
 	}

 	private List<IObserver> initObserverList(Class<? extends IObserver> iface) {
 		List<IObserver> list = observerMap.get(iface);
 		if (list == null) {
 			list = new ArrayList<IObserver>();
 			observerMap.put(iface, list);
 		}
 		return list;
 	}

 	private List<IObserver> getObserverByClass(Class<? extends IObserver> clazz) {
 		List<IObserver> list = observerMap.get(clazz);
 		if (list == null) {
 			list = Collections.emptyList();
 		}
 		return new ArrayList<IObserver>(list);
 	}

 	private boolean isPrioritizedObserver(Class<?> clazz, Method method) {
 		// Only prioritize if requested class extends PrioritizedIObserver and method is part of this class and not part
 		// of some super class
 		if (!clazz.equals(method.getDeclaringClass())) {
 			return false;
 		}
 		for (Class<?> interfaceClass : clazz.getInterfaces()) {
 			if (PrioritizedIObserver.class.equals(interfaceClass)) {
 				return true;
 			}
 		}
 		return false;
 	}

 	@SuppressWarnings("unchecked")
 	private <T extends IObserver> T createProxy(Class<T> clazz, boolean prioritized) {
 		ProxyHandler handler = new ProxyHandler((Class<IObserver>) clazz, prioritized);
 		return (T) Proxy.newProxyInstance(clazz.getClassLoader(), new Class[] { clazz, ObserverCall.class }, handler);

 	}

 	/**
 	 * Proxyobserver which notifies all observers.
 	 *
 	 * @author wesendon
 	 */
 	private final class ProxyHandler implements InvocationHandler, ObserverCall {

 		private Class<IObserver> clazz;
 		private List<ObserverCall.Result> lastResults;
 		private boolean prioritized;

 		public ProxyHandler(Class<IObserver> clazz, boolean prioritized) {
 			this.clazz = clazz;
 			this.prioritized = prioritized;
 			this.lastResults = new ArrayList<ObserverCall.Result>();
 		}

 		// BEGIN SUPRESS CATCH EXCEPTION
 		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 			// END SUPRESS CATCH EXCEPTION
 			// fork for calls to ObserverCall.class
 			if (ObserverCall.class.equals(method.getDeclaringClass())) {
 				return accessObserverCall(method, args);
 			}

 			List<IObserver> observers = getObserverByClass(clazz);

 			if (prioritized && isPrioritizedObserver(clazz, method)) {
 				sortObservers(observers);
 			}

 			// return default value if no observers are registered
 			if (observers.size() == 0) {
 				lastResults = new ArrayList<ObserverCall.Result>();
 				return Result.getDefaultValue(method);
 			}

 			lastResults = notifiyObservers(observers, method, args);
 			return lastResults.get(0).getResultOrDefaultValue();
 		}

 		private Object accessObserverCall(Method method, Object[] args) throws IllegalArgumentException,
 			IllegalAccessException, InvocationTargetException {
 			return method.invoke(this, args);

 		}

 		private List<ObserverCall.Result> notifiyObservers(List<IObserver> observers, Method method, Object[] args) {
 			List<ObserverCall.Result> results = new ArrayList<ObserverCall.Result>(observers.size());
 			for (IObserver observer : observers) {
 				try {
 					results.add(new Result(observer, method, method.invoke(observer, args)));
 				// BEGIN SUPRESS CATCH EXCEPTION
 				} catch (Throwable e) {
 				// END SUPRESS CATCH EXCEPTION
 					results.add(new Result(observer, e, method));
 				}
 			}
 			return results;
 		}

 		public List<Result> getObserverCallResults() {
 			return lastResults;
 		}

 		// END SUPRESS CATCH EXCEPTION
 	}

 	/**
 	 * Sorts Observers. Make sure they are {@link PrioritizedIObserver}!!
 	 *
 	 * @param observers list of observers
 	 */
 	private void sortObservers(List<IObserver> observers) {
 		Collections.sort(observers, new Comparator<IObserver>() {
 			public int compare(IObserver o1, IObserver o2) {
 				int prio1 = ((PrioritizedIObserver) o1).getPriority();
 				int prio2 = ((PrioritizedIObserver) o2).getPriority();
 				if (prio1 == prio2) {
 					return 0;
 				}
 				return (prio1 > prio2) ? 1 : -1;
 			}
 		});
 	}

 	@SuppressWarnings("unchecked")
 	private Class<? extends IObserver>[] getObserverInterfaces(IObserver observer) {
 		HashSet<Class<? extends IObserver>> observerInterfacsFound = new HashSet<Class<? extends IObserver>>();
 		getClasses(observer.getClass(), observerInterfacsFound);
 		return observerInterfacsFound.toArray(new Class[observerInterfacsFound.size()]);
 	}

 	@SuppressWarnings("unchecked")
 	private boolean getClasses(Class<?> clazz, HashSet<Class<? extends IObserver>> result) {
 		for (Class<?> iface : getAllInterfaces(clazz, new HashSet<Class<?>>())) {
 			if (iface.equals(IObserver.class) && clazz.isInterface()) {
 				result.add((Class<? extends IObserver>) clazz);
 				return true;
 			} else {
 				if (getClasses(iface, result) && clazz.isInterface()) {
 					result.add((Class<? extends IObserver>) clazz);
 				}
 			}
 		}
 		return false;
 	}

 	private Set<Class<?>> getAllInterfaces(final Class<?> clazz, final Set<Class<?>> interfacesFound) {

 		for (Class<?> iface : clazz.getInterfaces()) {
 			interfacesFound.add((Class<?>) iface);
 		}

 		if (clazz.getSuperclass() == null) {
 			return interfacesFound;
 		}

 		return getAllInterfaces(clazz.getSuperclass(), interfacesFound);
 	}

 	/**
 	 * Pulls observers from an extensionpoint and registers them.
 	 */
 	public void collectionExtensionPoints() {
 		for (ExtensionElement outer : new ExtensionPoint("org.eclipse.emf.emfstore.common.observer", true)
 			.getExtensionElements()) {
 			try {
 				for (ExtensionElement inner : new ExtensionPoint(outer.getAttribute("extensionPointName"), true)
 					.getExtensionElements()) {
 					register(inner.getClass(outer.getAttribute("observerAttributeName"), IObserver.class));
 				}
 			} catch (ExtensionPointException e) {
 			}
 		}
 	}
 }
	/*******************************************************************************
	* Copyright 2011 Chair for Applied Software Engineering,
	* Technische Universitaet Muenchen.
	* All rights reserved. This program and the accompanying materials
	* are made available under the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	******************************************************************************/
	package org.eclipse.emf.emfstore.common.observer;

	import java.lang.reflect.InvocationHandler;
	import java.lang.reflect.InvocationTargetException;
	import java.lang.reflect.Method;
	import java.lang.reflect.Proxy;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Set;

	import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionElement;
	import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPoint;
	import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPointException;

	/**
	* This is a universal observer bus. This class follows the publish/subscribe pattern, it is a central dispatcher for
	* observers and makes use of generics in order to allow type safety. It can be used as singleton or be injected through
	* DI.
	* Observers have to implement the {@link IObserver} interface, which is only used as a marker. Future use of
	* Annotations is possible.
	* by using {@link #notify(Class)} (e.g. <code>bus.notify(MyObserver.class).myObserverMethod()</code>) all registered
	* Observers are notified.
	* This is implemented by using the java {@link Proxy} class. By calling {@link #notify(Class)} a proxy is returned,
	* which then calls all registered observers.
	* The proxy can also be casted into {@link ObserverCall}, which allows to access all results by the different
	* observers.
	*
	*
	* Example code:
	*
	* <pre>
	* // A is IObserver
	* A a = new A() {
	*
	* public void foo() {
	* System.out.println("A says: go!");
	* }
	* };
	*
	* // B extends A and is IObserver
	* B b = new B() {
	*
	* public void say(String ja) {
	* System.out.println("B says: " + ja);
	* }
	*
	* public void foo() {
	* System.out.println("B says: h??");
	* }
	* };
	*
	* // B is registered first
	* ObserverBus.register(b);
	* ObserverBus.register(a);
	*
	* ObserverBus.notify(A.class).foo();
	*
	* ObserverBus.notify(B.class).say("w00t");
	*
	* // Output:
	*
	* // B says: h??
	* // A says: go!
	* //
	* // B says: w00t
	*
	* </pre>
	*
	* @author wesendon
	*/
	public class ObserverBus {

	/**
	* Initializes the singleton instance statically.
	*/
	private static class SingletonHolder {
	public static final ObserverBus INSTANCE = new ObserverBus();
	}

	/**
	* Static ObserverBus singleton. Use of singleton is optional, for that reason the constructor is public.
	*
	* @return Static instance of the observerbus
	*/
	public static ObserverBus getInstance() {
	return SingletonHolder.INSTANCE;
	}

	private HashMap<Class<? extends IObserver>, List<IObserver>> observerMap;

	/**
	* Default constructor.
	*/
	public ObserverBus() {
	observerMap = new HashMap<Class<? extends IObserver>, List<IObserver>>();
	collectionExtensionPoints();
	}

	/**
	* This method allows you to notify all observers.
	*
	* @param <T> class of observer
	* @param clazz class of observer
	* @return call object
	*/
	public <T extends IObserver> T notify(Class<T> clazz) {
	return (T) notify(clazz, false);
	}

	/**
	* This method allows you to notify all observers.
	*
	* @param <T> class of observer
	* @param clazz class of observer
	* @param prioritized sort observer after {@link PrioritizedIObserver}
	*
	* @return call object
	*/
	public <T extends IObserver> T notify(Class<T> clazz, boolean prioritized) {
	if (clazz == null) {
	return null;
	}
	return (T) createProxy(clazz, false);
	}

	/**
	* Registers an observer for all observer interfaces implemented by the object or its super classes.
	*
	* @param observer observer object
	*/
	public void register(IObserver observer) {
	register(observer, getObserverInterfaces(observer));
	}

	/**
	* Registers an observer for the specified observer interfaces.
	*
	* @param observer observer object
	* @param classes set of classes
	*/
	public void register(IObserver observer, Class<? extends IObserver>... classes) {
	for (Class<? extends IObserver> iface : classes) {
	if (iface.isInstance(observer)) {
	addObserver(observer, iface);
	}
	}
	}

	/**
	* Unregisters an observer for all observer interfaces implemented by the object or its super classes.
	*
	* @param observer observer object
	*/
	public void unregister(IObserver observer) {
	unregister(observer, getObserverInterfaces(observer));
	}

	/**
	* Unregisters an observer for the specified observer interfaces.
	*
	* @param observer observer object
	* @param classes set of classes
	*/
	public void unregister(IObserver observer, Class<? extends IObserver>... classes) {
	for (Class<? extends IObserver> iface : classes) {
	if (iface.isInstance(observer)) {
	removeObserver(observer, iface);
	}
	}
	}

	private void addObserver(IObserver observer, Class<? extends IObserver> iface) {
	List<IObserver> observers = initObserverList(iface);
	observers.add(observer);
	}

	private void removeObserver(IObserver observer, Class<? extends IObserver> iface) {
	List<IObserver> observers = initObserverList(iface);
	observers.remove(observer);
	}

	private List<IObserver> initObserverList(Class<? extends IObserver> iface) {
	List<IObserver> list = observerMap.get(iface);
	if (list == null) {
	list = new ArrayList<IObserver>();
	observerMap.put(iface, list);
	}
	return list;
	}

	private List<IObserver> getObserverByClass(Class<? extends IObserver> clazz) {
	List<IObserver> list = observerMap.get(clazz);
	if (list == null) {
	list = Collections.emptyList();
	}
	return new ArrayList<IObserver>(list);
	}

	private boolean isPrioritizedObserver(Class<?> clazz, Method method) {
	// Only prioritize if requested class extends PrioritizedIObserver and method is part of this class and not part
	// of some super class
	if (!clazz.equals(method.getDeclaringClass())) {
	return false;
	}
	for (Class<?> interfaceClass : clazz.getInterfaces()) {
	if (PrioritizedIObserver.class.equals(interfaceClass)) {
	return true;
	}
	}
	return false;
	}

	@SuppressWarnings("unchecked")
	private <T extends IObserver> T createProxy(Class<T> clazz, boolean prioritized) {
	ProxyHandler handler = new ProxyHandler((Class<IObserver>) clazz, prioritized);
	return (T) Proxy.newProxyInstance(clazz.getClassLoader(), new Class[] { clazz, ObserverCall.class }, handler);

	}

	/**
	* Proxyobserver which notifies all observers.
	*
	* @author wesendon
	*/
	private final class ProxyHandler implements InvocationHandler, ObserverCall {

	private Class<IObserver> clazz;
	private List<ObserverCall.Result> lastResults;
	private boolean prioritized;

	public ProxyHandler(Class<IObserver> clazz, boolean prioritized) {
	this.clazz = clazz;
	this.prioritized = prioritized;
	this.lastResults = new ArrayList<ObserverCall.Result>();
	}

	// BEGIN SUPRESS CATCH EXCEPTION
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
	// END SUPRESS CATCH EXCEPTION
	// fork for calls to ObserverCall.class
	if (ObserverCall.class.equals(method.getDeclaringClass())) {
	return accessObserverCall(method, args);
	}

	List<IObserver> observers = getObserverByClass(clazz);

	if (prioritized && isPrioritizedObserver(clazz, method)) {
	sortObservers(observers);
	}

	// return default value if no observers are registered
	if (observers.size() == 0) {
	lastResults = new ArrayList<ObserverCall.Result>();
	return Result.getDefaultValue(method);
	}

	lastResults = notifiyObservers(observers, method, args);
	return lastResults.get(0).getResultOrDefaultValue();
	}

	private Object accessObserverCall(Method method, Object[] args) throws IllegalArgumentException,
	IllegalAccessException, InvocationTargetException {
	return method.invoke(this, args);

	}

	private List<ObserverCall.Result> notifiyObservers(List<IObserver> observers, Method method, Object[] args) {
	List<ObserverCall.Result> results = new ArrayList<ObserverCall.Result>(observers.size());
	for (IObserver observer : observers) {
	try {
	results.add(new Result(observer, method, method.invoke(observer, args)));
	// BEGIN SUPRESS CATCH EXCEPTION
	} catch (Throwable e) {
	// END SUPRESS CATCH EXCEPTION
	results.add(new Result(observer, e, method));
	}
	}
	return results;
	}

	public List<Result> getObserverCallResults() {
	return lastResults;
	}

	// END SUPRESS CATCH EXCEPTION
	}

	/**
	* Sorts Observers. Make sure they are {@link PrioritizedIObserver}!!
	*
	* @param observers list of observers
	*/
	private void sortObservers(List<IObserver> observers) {
	Collections.sort(observers, new Comparator<IObserver>() {
	public int compare(IObserver o1, IObserver o2) {
	int prio1 = ((PrioritizedIObserver) o1).getPriority();
	int prio2 = ((PrioritizedIObserver) o2).getPriority();
	if (prio1 == prio2) {
	return 0;
	}
	return (prio1 > prio2) ? 1 : -1;
	}
	});
	}

	@SuppressWarnings("unchecked")
	private Class<? extends IObserver>[] getObserverInterfaces(IObserver observer) {
	HashSet<Class<? extends IObserver>> observerInterfacsFound = new HashSet<Class<? extends IObserver>>();
	getClasses(observer.getClass(), observerInterfacsFound);
	return observerInterfacsFound.toArray(new Class[observerInterfacsFound.size()]);
	}

	@SuppressWarnings("unchecked")
	private boolean getClasses(Class<?> clazz, HashSet<Class<? extends IObserver>> result) {
	for (Class<?> iface : getAllInterfaces(clazz, new HashSet<Class<?>>())) {
	if (iface.equals(IObserver.class) && clazz.isInterface()) {
	result.add((Class<? extends IObserver>) clazz);
	return true;
	} else {
	if (getClasses(iface, result) && clazz.isInterface()) {
	result.add((Class<? extends IObserver>) clazz);
	}
	}
	}
	return false;
	}

	private Set<Class<?>> getAllInterfaces(final Class<?> clazz, final Set<Class<?>> interfacesFound) {

	for (Class<?> iface : clazz.getInterfaces()) {
	interfacesFound.add((Class<?>) iface);
	}

	if (clazz.getSuperclass() == null) {
	return interfacesFound;
	}

	return getAllInterfaces(clazz.getSuperclass(), interfacesFound);
	}

	/**
	* Pulls observers from an extensionpoint and registers them.
	*/
	public void collectionExtensionPoints() {
	for (ExtensionElement outer : new ExtensionPoint("org.eclipse.emf.emfstore.common.observer", true)
	.getExtensionElements()) {
	try {
	for (ExtensionElement inner : new ExtensionPoint(outer.getAttribute("extensionPointName"), true)
	.getExtensionElements()) {
	register(inner.getClass(outer.getAttribute("observerAttributeName"), IObserver.class));
	}
	} catch (ExtensionPointException e) {
	}
	}
	}
	}