package de.idos.updates.util;
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.List;
//Nat Pryce's Announcer, taken from jmock examples: http://nat.truemesh.com/archives/000710.html
public class Announcer<T> {
private final T proxy;
private final List<T> listeners = new ArrayList<T>();
public Announcer(Class<? extends T> listenerType) {
proxy = listenerType.cast(Proxy.newProxyInstance(
listenerType.getClassLoader(),
new Class<?>[]{listenerType},
new InvocationHandler() {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
announce(method, args);
return null;
}
}));
}
public void addListener(T listener) {
listeners.add(listener);
}
public void removeListener(T listener) {
listeners.remove(listener);
}
public T announce() {
return proxy;
}
private void announce(Method m, Object[] args) {
try {
for (T listener : new ArrayList<T>(listeners)) {
m.invoke(listener, args);
}
}
catch (IllegalAccessException e) {
throw new IllegalArgumentException("could not invoke listener", e);
}
catch (InvocationTargetException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException) {
throw (RuntimeException)cause;
}
else if (cause instanceof Error) {
throw (Error)cause;
}
else {
throw new UnsupportedOperationException("listener threw exception", cause);
}
}
}
public static <T> Announcer<T> to(Class<? extends T> listenerType) {
return new Announcer<T>(listenerType);
}
}