/*
* 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.AfterEvent;
import org.apache.openejb.observer.event.BeforeEvent;
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.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ObserverManager {
private static final ThreadLocal<Set<Invocation>> seen = new ThreadLocal<Set<Invocation>>() {
@Override
protected Set<Invocation> initialValue() {
return new HashSet<Invocation>();
}
};
// lazy init since it is used in SystemInstance
private static final AtomicReference<Logger> LOGGER = new AtomicReference<Logger>();
private final Set<Observer> observers = new LinkedHashSet<Observer>();
private final Map<Class, Invocation> methods = new ConcurrentHashMap<Class, Invocation>();
public boolean addObserver(final Object observer) {
if (observer == null) {
throw new IllegalArgumentException("observer cannot be null");
}
try {
final Observer wrapper = new Observer(observer);
if (wrapper.after.size() + wrapper.before.size() + wrapper.methods.size() > 0 && observers.add(wrapper)) {
methods.clear();
fireEvent(new ObserverAdded(observer));
return true;
} else {
return false;
}
} catch (final NotAnObserverException naoe) {
return false;
}
}
public boolean removeObserver(final Object observer) {
if (observer == null) {
throw new IllegalArgumentException("listener cannot be null");
}
try {
if (observers.remove(new Observer(observer))) {
methods.clear();
fireEvent(new ObserverRemoved(observer));
return true;
} else {
return false;
}
} catch (final NotAnObserverException naoe) {
return false;
}
}
public <E> E fireEvent(final E event) {
if (event == null) {
throw new IllegalArgumentException("event cannot be null");
}
try {
return doFire(event);
} finally {
seen.remove();
}
}
private <E> E doFire(final E event) {
final Class<?> type = event.getClass();
final Invocation invocation = getInvocation(type);
invocation.invoke(event);
return event;
}
private Invocation getInvocation(final Class<?> type) {
{
final Invocation invocation = methods.get(type);
if (invocation != null) {
return invocation;
}
}
final Invocation invocation = buildInvocation(type);
methods.put(type, invocation);
return invocation;
}
public void destroy() {
for (final Observer o : new LinkedList<>(observers)) {
removeObserver(o.observer);
}
}
private static enum Phase {
BEFORE,
INVOKE,
AFTER
}
private Invocation buildInvocation(final Class<?> type) {
final Invocation before = buildInvocation(Phase.BEFORE, type);
final Invocation after = buildInvocation(Phase.AFTER, type);
final Invocation invoke = buildInvocation(Phase.INVOKE, type);
if (IGNORE == before && IGNORE == after) {
return invoke;
} else {
return new BeforeAndAfterInvocationSet(before, invoke, after);
}
}
private Invocation buildInvocation(final Phase phase, final Class<?> type) {
final InvocationList list = new InvocationList();
for (final Observer observer : observers) {
final Invocation method = observer.get(phase, type);
if (method != null && method != IGNORE) {
list.add(method);
}
}
if (list.getInvocations().size() == 0) {
return IGNORE;
} else if (list.getInvocations().size() == 1) {
return list.getInvocations().get(0);
} else {
return list;
}
}
/**
* @version $Rev$ $Date$
*/
public class Observer {
private final Map<Class, Invocation> before = new ConcurrentHashMap<Class, Invocation>();
private final Map<Class, Invocation> methods = new ConcurrentHashMap<Class, Invocation>();
private final Map<Class, Invocation> after = new ConcurrentHashMap<Class, Invocation>();
private final Object observer;
public Observer(final Object observer) {
if (observer == null) {
throw new IllegalArgumentException("observer cannot be null");
}
final Set<Method> methods = new HashSet<Method>();
methods.addAll(Arrays.asList(observer.getClass().getMethods()));
methods.addAll(Arrays.asList(observer.getClass().getDeclaredMethods()));
this.observer = observer;
for (final Method method : methods) {
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.isStatic(method.getModifiers())) {
throw new IllegalArgumentException("@Observes method must not be static: " + method.toString());
}
if (!Modifier.isPublic(method.getModifiers())) {
throw new IllegalArgumentException("@Observes method must be public: " + method.toString());
}
final Class<?> type = method.getParameterTypes()[0];
if (AfterEvent.class.equals(type)) {
final Class parameterClass = getParameterClass(method);
this.after.put(parameterClass, new AfterInvocation(method, observer));
} else if (BeforeEvent.class.equals(type)) {
final Class parameterClass = getParameterClass(method);
this.before.put(parameterClass, new BeforeInvocation(method, observer));
} else {
validate(method, type);
this.methods.put(type, new MethodInvocation(method, observer));
}
}
if (methods.size() == 0 && after.size() == 0 && before.size() == 0) {
throw new NotAnObserverException("Object has no @Observes methods. For example: public void observe(@Observes RetryConditionAdded event){...}");
}
}
private Class getParameterClass(final Method method) {
final Type[] genericParameterTypes = method.getGenericParameterTypes();
final Type generic = genericParameterTypes[0];
if (!(generic instanceof ParameterizedType)) {
final Class<?> event = method.getParameterTypes()[0];
throw new IllegalArgumentException("@Observes " + event.getSimpleName() + " missing generic type: " + method.toString());
}
final ParameterizedType parameterized = ParameterizedType.class.cast(generic);
final Type type = parameterized.getActualTypeArguments()[0];
final Class clazz;
if (type instanceof Class) {
clazz = Class.class.cast(type);
} else if (type instanceof WildcardType) {
clazz = Object.class;
} else {
final Class<?> event = method.getParameterTypes()[0];
throw new IllegalArgumentException("@Observes " + event.getSimpleName() + " unsupported generic type: " + type.getClass().getSimpleName() + " " + method.toString());
}
validate(method, clazz);
return clazz;
}
private void validate(final Method method, final Class<?> type) {
if (type.isAnnotation()) {
throw new IllegalArgumentException("@Observes method parameter must be a concrete class (not an annotation): " + 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());
}
}
private Map<Class, Invocation> map(final Phase event) {
switch (event) {
case AFTER:
return after;
case BEFORE:
return before;
case INVOKE:
return methods;
default:
throw new IllegalStateException("Unknown Event style " + event);
}
}
public Invocation get(final Phase event, final Class eventType) {
return get(map(event), eventType);
}
public Invocation getAfter(final Class eventType) {
return get(after, eventType);
}
public Invocation getBefore(final Class eventType) {
return get(before, eventType);
}
private Invocation get(final Map<Class, Invocation> map, final Class eventType) {
if (eventType == null) {
return IGNORE;
}
final Invocation method = map.get(eventType);
if (method != null) {
return method;
}
return get(map, eventType.getSuperclass());
}
private boolean isObserver(final Method method) {
for (final Annotation[] annotations : method.getParameterAnnotations()) {
for (final Annotation annotation : annotations) {
if (annotation.annotationType().equals(Observes.class)) {
return true;
}
}
}
return false;
}
@Override
public boolean equals(final 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();
}
}
public interface Invocation {
void invoke(Object event);
}
private static final Invocation IGNORE = new Invocation() {
@Override
public void invoke(final Object event) {
}
@Override
public String toString() {
return "IGNORE";
}
};
public class MethodInvocation implements Invocation {
private final Method method;
private final Object observer;
public MethodInvocation(final Method method, final Object observer) {
this.method = method;
this.observer = observer;
}
@Override
public void invoke(final Object event) {
try {
method.invoke(observer, event);
} catch (final InvocationTargetException e) {
if (!seen.get().add(this)) {
return;
}
final Throwable t = e.getTargetException() == null ? e : e.getTargetException();
if (!(event instanceof ObserverFailed)) {
doFire(new ObserverFailed(observer, method, event, t));
}
if (t instanceof InvocationTargetException && t.getCause() != null) {
ObserverManager.logger().log(Level.SEVERE, "error invoking " + observer, t.getCause());
} else {
ObserverManager.logger().log(Level.SEVERE, "error invoking " + observer, t);
}
} catch (final IllegalAccessException e) {
ObserverManager.logger().log(Level.SEVERE, method + " can't be invoked, check it is public");
}
}
@Override
public String toString() {
return method.toString();
}
}
// done lazily since this class is used in SystemInstance
private static Logger logger() {
Logger value = LOGGER.get();
if (value == null) {
value = Logger.getLogger(ObserverManager.class.getName());
LOGGER.set(value);
}
return value;
}
private final class AfterInvocation extends MethodInvocation {
private AfterInvocation(final Method method, final Object observer) {
super(method, observer);
}
@Override
public void invoke(final Object event) {
super.invoke(new AfterEvent() {
@Override
public Object getEvent() {
return event;
}
public String toString() {
return "AfterEvent{} " + event;
}
});
}
}
private final class BeforeInvocation extends MethodInvocation {
private BeforeInvocation(final Method method, final Object observer) {
super(method, observer);
}
@Override
public void invoke(final Object event) {
super.invoke(new BeforeEvent() {
@Override
public Object getEvent() {
return event;
}
public String toString() {
return "BeforeEvent{} " + event;
}
});
}
}
private static final class BeforeAndAfterInvocationSet implements Invocation {
private final Invocation before;
private final Invocation invoke;
private final Invocation after;
private BeforeAndAfterInvocationSet(final Invocation before, final Invocation invoke, final Invocation after) {
this.before = before;
this.invoke = invoke;
this.after = after;
}
@Override
public void invoke(final Object event) {
before.invoke(event);
invoke.invoke(event);
after.invoke(event);
}
}
public static class InvocationList implements Invocation {
private final List<Invocation> invocations = new LinkedList<Invocation>();
public boolean add(final Invocation invocation) {
return invocations.add(invocation);
}
public List<Invocation> getInvocations() {
return invocations;
}
@Override
public void invoke(final Object event) {
for (final Invocation invocation : invocations) {
invocation.invoke(event);
}
}
}
public static class NotAnObserverException extends IllegalArgumentException {
public NotAnObserverException(final String s) {
super(s);
}
}
}