Add typed Message.getMessageObserver(Class).

Signed-off-by: Achim Kraus <[email protected]>

californium-core/src/main/java/org/eclipse/californium/core/coap/Message.java

@@ -1308,6 +1308,7 @@ public void setProtectFromOffload() {
 	 * Returns the observers registered for this message.
 	 * 
 	 * @return an immutable list of the registered observers.
+	 * @see #getMessageObservers(Class)
 	 * @see #addMessageObserver(MessageObserver)
 	 * @see #addMessageObserver(int, MessageObserver)
 	 * @see #addMessageObservers(List)
@@ -1321,6 +1322,32 @@ public List<MessageObserver> getMessageObservers() {
 		}
 	}
 
+	/**
+	 * Returns the observer of the provided type registered for this message.
+	 * 
+	 * @param type type of observers
+	 * @return the registered observers of that type, or {@code null}, if not
+	 *         available.
+	 * @see #getMessageObservers()
+	 * @see #addMessageObserver(MessageObserver)
+	 * @see #addMessageObserver(int, MessageObserver)
+	 * @see #addMessageObservers(List)
+	 * @see #removeMessageObserver(MessageObserver)
+	 * @since 3.3
+	 */
+	@SuppressWarnings("unchecked")
+	public <T extends MessageObserver> T getMessageObserver(Class<T> type) {
+		List<MessageObserver> list = unmodifiableMessageObserversFacade;
+		if (null != list) {
+			for (MessageObserver obs : list) {
+				if (type.isInstance(obs)) {
+					return (T) obs;
+				}
+			}
+		}
+		return null;
+	}
+
 	/**
 	 * Adds the specified message observer.
 	 *