ResourceExistsAction


1   /*
2    * Copyright 1999-2004 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.acting;
17  
18  import org.apache.avalon.framework.parameters.Parameters;
19  import org.apache.avalon.framework.thread.ThreadSafe;
20  import org.apache.cocoon.environment.Redirector;
21  import org.apache.cocoon.environment.SourceResolver;
22  import org.apache.excalibur.source.Source;
23  import org.apache.excalibur.source.SourceNotFoundException;
24  
25  import java.util.Map  ;
26  
27  /**
28   * This action simply checks to see if a resource identified by the <code>src</code>
29   * sitemap attribute exists or not. The action returns empty <code>Map</code> if
30   * resource exists, <code>null</code> otherwise.
31   * 
32   * <p>Instead of src attribute, source can be specified using
33   * parameter named <code>url</code> (this is old syntax, should be removed soon).
34   * 
35   * <p><b>NOTE:</b> {@link org.apache.cocoon.selection.ResourceExistsSelector}
36   * should be preferred to this component, as the semantics of a Selector better
37   * matches the supplied functionality.
38   *
39   * @author <a HREF="mailto:balld@apache.org">Donald Ball</a>
40   * @version CVS $Id: ResourceExistsAction.java 30932 2004-07-29 17:35:38Z vgritsenko $
41   */
42  public class ResourceExistsAction extends ServiceableAction implements ThreadSafe {
43  
44      public Map   act(Redirector redirector, SourceResolver resolver, Map   objectModel, String   src, Parameters parameters) throws Exception   {
45          String   resourceURI = parameters.getParameter("url", src);
46          Source source = null;
47          try {
48              source = resolver.resolveURI(resourceURI);
49              if (source.exists()) {
50                  return EMPTY_MAP;
51              }
52          } catch (SourceNotFoundException e) {
53              // Do not log
54          } catch (Exception   e) {
55              getLogger().warn("Exception resolving resource " + resourceURI, e);
56          } finally {
57              if (source != null) {
58                  resolver.release(source);
59              }
60          }
61          return null;
62      }
63  }
64
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