Extend annotation.

org.jgrapes.core/src/org/jgrapes/core/annotation/Handler.java

@@ -80,8 +80,8 @@
  * Finally, independent of any specified channels, the matching algorithm 
  * invokes {@link Eligible#isEligibleFor(Object) isEligibleFor} 
  * for each of the event's channels with the component's default criterion
- * as argument. This results in a match if
- * the component itself is used as one of the event's channels
+ * as argument unless {@link #excludeSelf()} is set. This results in a match
+ * if the component itself is used as one of the event's channels
  * (see the description of {@link Eligible}).
  * 
  * If a match is found for a given event's properties and a handler's
@@ -265,6 +265,26 @@ final class NoChannel extends ClassChannel {
      */
     boolean dynamic() default false;
 
+    /**
+     * Excludes the handler from channel matching against its component's
+     * default criterion. The typical use case for this annotation is
+     * a converter component that receives events from some source channel
+     * and then fires the same kind of events with modified data using 
+     * itself as the (source) channel. In this case, the events
+     * generated by the component must not be processed by the component
+     * although they are fired using the component as channel. So while it
+     * is useful to be able to target a specific component (using it as 
+     * channel) in general, it isn't in this special case and can therefore
+     * be turned off with this annotation.
+     * 
+     * Of course, it would also be possible to work around the ambiguity
+     * by firing the conversion results on an extra channel. But it is 
+     * quite intuitive to use the component itself as (source) channel.
+     *
+     * @return true, if set
+     */
+    boolean excludeSelf() default false;
+
     /**
      * This class provides the {@link Evaluator} for the 
      * {@link Handler} annotation provided by the core package. It 
@@ -495,7 +515,7 @@ public Scope(ComponentType component, Method method,
                 }
                 // Finally, a component always handles events
                 // directed at it directly.
-                if (component instanceof Channel) {
+                if (component instanceof Channel && !annotation.excludeSelf()) {
                     channelCriteria.add(
                         ((Channel) component).defaultCriterion());
                 }