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 import org.apache.velocity.context.Context;
23 import org.apache.velocity.util.ContextAware;
24
25 /**
26 * Reference 'Stream insertion' event handler. Called with object
27 * that will be inserted into stream via value.toString().
28 *
29 * Please return an Object that will toString() nicely :)
30 *
31 * @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a>
32 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
33 * @version $Id: ReferenceInsertionEventHandler.java 470256 2006-11-02 07:20:36Z wglass $
34 */
35 public interface ReferenceInsertionEventHandler extends EventHandler
36 {
37 /**
38 * A call-back which is executed during Velocity merge before a reference
39 * value is inserted into the output stream. All registered
40 * ReferenceInsertionEventHandlers are called in sequence. If no
41 * ReferenceInsertionEventHandlers are are registered then reference value
42 * is inserted into the output stream as is.
43 *
44 * @param reference Reference from template about to be inserted.
45 * @param value Value about to be inserted (after its <code>toString()</code>
46 * method is called).
47 * @return Object on which <code>toString()</code> should be called for
48 * output.
49 */
50 public Object referenceInsert( String reference, Object value );
51
52 /**
53 * Defines the execution strategy for referenceInsert
54 */
55 static class referenceInsertExecutor implements EventHandlerMethodExecutor
56 {
57 private Context context;
58 private String reference;
59 private Object value;
60
61 referenceInsertExecutor(
62 Context context,
63 String reference,
64 Object value)
65 {
66 this.context = context;
67 this.reference = reference;
68 this.value = value;
69 }
70
71 /**
72 * Call the method referenceInsert()
73 *
74 * @param handler call the appropriate method on this handler
75 */
76 public void execute(EventHandler handler)
77 {
78 ReferenceInsertionEventHandler eh = (ReferenceInsertionEventHandler) handler;
79
80 if (eh instanceof ContextAware)
81 ((ContextAware) eh).setContext(context);
82
83 /**
84 * Every successive call will alter the same value
85 */
86 value = ((ReferenceInsertionEventHandler) handler).referenceInsert(reference, value);
87 }
88
89 public Object getReturnValue()
90 {
91 return value;
92 }
93
94 /**
95 * Continue to end of event handler iteration
96 *
97 * @return always returns false
98 */
99 public boolean isDone()
100 {
101 return false;
102 }
103 }
104
105 }