1 package org.apache.velocity.app.event;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 /**
23 * Strategy object used to execute event handler method. Will be called
24 * while looping through all the chained event handler implementations.
25 * Each EventHandler method call should have a parallel executor object
26 * defined.
27 *
28 * @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a>
29 * @version $Id: EventHandlerMethodExecutor.java 685685 2008-08-13 21:43:27Z nbubna $
30 * @since 1.5
31 */
32 public interface EventHandlerMethodExecutor
33 {
34 /**
35 * Execute the event handler method. If Object is not null, do not
36 * iterate further through the handler chain.
37 * If appropriate, the returned Object will be the return value.
38 *
39 * @param handler call the appropriate method on this handler
40 * @exception Exception generic exception potentially thrown by event handlers
41 */
42 public void execute(EventHandler handler) throws Exception;
43
44 /**
45 * Called after execute() to see if iterating should stop. Should
46 * always return false before method execute() is run.
47 *
48 * @return true if no more event handlers for this method should be called.
49 */
50 public boolean isDone();
51
52 /**
53 * Get return value at end of all the iterations
54 *
55 * @return null if no return value is required
56 */
57 public Object getReturnValue();
58 }