import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
// Concrete EventBus implementation
public class SimpleEventBus<T> implements MyEventBus<T> {
private final ConcurrentHashMap<String, List<MyEventListener<T>>> listenersMap = new ConcurrentHashMap<>();
// Publish an event to all listeners of a source
public void push(String source, T event) {
List<MyEventListener<T>> listeners = listenersMap.get(source);
if (listeners != null && !listeners.isEmpty()) {
for (MyEventListener<T> listener : listeners) {
try {
listener.onEvent(source, event);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
// Get number of subscribers for a source
public int getSubscriberCount(String source) {
List<MyEventListener<T>> listeners = listenersMap.get(source);
return (listeners == null) ? 0 : listeners.size();
}
@Override
public void subscribe(String source, MyEventListener<T> listener) {
listenersMap.computeIfAbsent(source, key -> new CopyOnWriteArrayList<>()).add(listener);
}
@Override
public void unsubscribe(String source, MyEventListener<T> listener) {
listenersMap.computeIfPresent(source, (key, list) -> {
list.remove(listener);
return list.isEmpty() ? null : list;
});
}
}
အထက်ပေါ်ပြပါ EventBus မှာ Guava ၏ EventBus နှင့်ဆင်တူသော EventBus implementation ဖြစ်သည်။ အထူးတလည်ပင်ရှင်းပြရန်မလိုပေ။
class MessageListener implements MyEventListener<Message> {
private final String name;
public MessageListener(String name) { this.name = name; }
@Override
public void onEvent(String source, Message event) {
System.out.println(name + " received from [" + source + "]: " + event.getText());
}
}