EventAwareGenerator


1   /*
2    * Copyright 2005 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.cocoon.samples;
17  
18  import java.io.IOException  ;
19  import java.io.Serializable  ;
20  
21  import org.apache.cocoon.ProcessingException;
22  import org.apache.cocoon.caching.validity.EventValidity;
23  import org.apache.cocoon.caching.validity.NamedEvent;
24  import org.apache.cocoon.environment.ObjectModelHelper;
25  import org.apache.cocoon.environment.Request;
26  import org.apache.cocoon.generation.JXTemplateGenerator;
27  import org.apache.excalibur.source.SourceValidity;
28  import org.xml.sax.SAXException  ;
29  
30  /**
31   * This is a sample generator to demonstrate the event aware caching.
32   * We simply extend the JXTG.
33   * @version $Id: EventAwareGenerator.java 155005 2005-02-23 13:02:09Z cziegeler $
34   */
35  public class EventAwareGenerator extends JXTemplateGenerator {
36  
37      /**
38       * Generate the unique key for the cache.
39       *
40       * This key must be unique inside the space of this XSP page, it is used
41       * to find the page contents in the cache (if getValidity says that the
42       * contents are still valid).
43       *
44       * This method will be invoked before the getValidity() method.
45       *
46       * @return The generated key or null if the component
47       *         is currently not cacheable.
48       */
49      public Serializable   getKey() {
50          final Request request = ObjectModelHelper.getRequest(this.objectModel);
51          // for our test, pages having the same value of "pageKey" will share
52          // the same cache location
53          String   key = request.getParameter("pageKey") ;
54          return ((key==null||"".equals(key)) ? "one" : key);
55      }
56  
57      /**
58       * Generate the validity object, tells the cache how long to
59       * keep contents having this key around.  In this case, it will 
60       * be until an Event is retrieved matching the NamedEvent created below.
61       *
62       * Before this method can be invoked the getKey() method
63       * will be invoked.
64       *
65       * @return The generated validity object or null if the
66       *         component is currently not cacheable.
67       */
68      public SourceValidity getValidity() {
69          final Request request = ObjectModelHelper.getRequest(this.objectModel);
70          String   key = request.getParameter("pageKey") ;
71          return new EventValidity(
72                     new NamedEvent(
73                         (key==null||"".equals(key)) ? "one" : key));
74      }
75  
76  
77      /* (non-Javadoc)
78       * @see org.apache.cocoon.generation.Generator#generate()
79       */
80      public void generate() 
81      throws IOException  , SAXException  , ProcessingException {
82          super.generate();
83          // slowdown page generation.
84          long DELAY_SECS = this.parameters.getParameterAsLong("DELAY_SECS", 2);
85          try {
86            Thread.sleep(DELAY_SECS * 1000L);
87          } catch (InterruptedException   ie) {
88            // Not much that can be done...
89          }
90      }
91  }
92
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