/*
* 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.openejb.observer;
import org.apache.openejb.observer.event.ObserverAdded;
import org.apache.openejb.observer.event.ObserverFailed;
import org.apache.openejb.observer.event.ObserverRemoved;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ObserverManager {
private final List<Observer> observers = new ArrayList<Observer>();
public boolean addObserver(Object observer) {
if (observer == null) throw new IllegalArgumentException("observer cannot be null");
final Observer obs;
try {
obs = new Observer(observer);
} catch (NotAnObserverException naoe) {
return false;
}
final boolean added = observers.add(obs);
// Observers can observe they have been added and are active
fireEvent(new ObserverAdded(observer));
return added;
}
public boolean removeObserver(Object observer) {
if (observer == null) throw new IllegalArgumentException("observer cannot be null");
// Observers can observe they are to be removed
fireEvent(new ObserverRemoved(observer));
return observers.remove(new Observer(observer));
}
public void fireEvent(Object event) {
if (event == null) throw new IllegalArgumentException("event cannot be null");
for (Observer observer : observers) {
try {
observer.invoke(event);
} catch (Throwable t) {
if (!(event instanceof ObserverFailed)) {
fireEvent(new ObserverFailed(observer, event, t));
}
Logger.getLogger(ObserverManager.class.getName()).log(Level.SEVERE, "error invoking " + observer, t);
}
}
}
/**
* @version $Rev$ $Date$
*/
public static class Observer {
private final Map<Class, Method> methods = new HashMap<Class, Method>();
private final Object observer;
private final Method defaultMethod;
public Observer(Object observer) {
if (observer == null) throw new IllegalArgumentException("observer cannot be null");
this.observer = observer;
for (Method method : observer.getClass().getMethods()) {
if (!isObserver(method)) continue;
if (method.getParameterTypes().length > 1) {
throw new IllegalArgumentException("@Observes method must have only 1 parameter: " + method.toString());
}
if (Modifier.isAbstract(method.getModifiers())) {
throw new IllegalArgumentException("@Observes method must not be abstract: " + method.toString());
}
if (!Modifier.isPublic(method.getModifiers())) {
throw new IllegalArgumentException("@Observes method must be public: " + method.toString());
}
final Class<?> type = method.getParameterTypes()[0];
if (type.isAnnotation()) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not an annotation): " + method.toString());
}
if (Modifier.isAbstract(type.getModifiers())) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not an abstract class): " + method.toString());
}
if (type.isInterface()) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not an interface): " + method.toString());
}
if (type.isArray()) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not an array): " + method.toString());
}
if (type.isPrimitive()) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not a primitive): " + method.toString());
}
methods.put(type, method);
}
defaultMethod = methods.get(Object.class);
if (methods.size() == 0) {
throw new NotAnObserverException("Object has no @Observes methods. For example: public void observe(@Observes RetryConditionAdded event){...}");
}
}
public void invoke(Object event) throws InvocationTargetException, IllegalAccessException {
if (event == null) throw new IllegalArgumentException("event cannot be null");
final Class eventType = event.getClass();
final Method method = methods.get(eventType);
if (method != null) {
method.invoke(observer, event);
} else if (defaultMethod != null) {
defaultMethod.invoke(observer, event);
}
}
private boolean isObserver(Method method) {
for (Annotation[] annotations : method.getParameterAnnotations()) {
for (Annotation annotation : annotations) {
if (annotation.annotationType().equals(Observes.class)) return true;
}
}
return false;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
final Observer observer1 = (Observer) o;
return observer.equals(observer1.observer);
}
@Override
public int hashCode() {
return observer.hashCode();
}
}
private static class NotAnObserverException extends RuntimeException {
public NotAnObserverException(final String s) {
super(s);
}
}
}