/*
* Copyright 2012 Jason Miller
*
* Licensed 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 jj.event;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* <p>
* Marks a method as an event listener on all injector-created instances
* marked as {@link Subscriber}
*
* <p>
* The method must take a single parameter, which is the event type. The
* listener can be any access except private. It can return anything at
* all (including void), but the event system will disregard it.
*
* <p>
* Events can be any type, or any interface, with the exception of
* {@link Object}. Event delivery respects the class hierarchy, so
* subscribing to a base event will get delivery for all sub types.
* Due to type erasure, parameterized classes do not work.
*
* <p>
* No serious processing should be done in event listeners since you have no control over
* what thread is running. Also, throwing anything from a listener method is considered a
* programming error, and it will cause assertion errors to be thrown into unspecified
* parts of the system, so don't do it! The easiest way to comply with this advice is to
* inject the {@link jj.execution.TaskRunner} and do something like:
* <pre class="brush:java">
* {@literal @}Listener
* void event(final Event event) {
* taskRunner.execute(new ServerTask("processing event") { // or some other task type
* public void run() throws Exception {
* doSomethingInterestingWithThe(event);
* }
* });
* }
* </pre>
*
* @author jason
*
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Listener {
}