MediaFilter


1   /*
2    * MediaFilter.java
3    *
4    * Version: $Revision: 1.11 $
5    *
6    * Date: $Date: 2006/03/30 02:46:42 $
7    *
8    * Copyright (c) 2002-2005, Hewlett-Packard Company and Massachusetts
9    * Institute of Technology.  All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions are
13   * met:
14   *
15   * - Redistributions of source code must retain the above copyright
16   * notice, this list of conditions and the following disclaimer.
17   *
18   * - Redistributions in binary form must reproduce the above copyright
19   * notice, this list of conditions and the following disclaimer in the
20   * documentation and/or other materials provided with the distribution.
21   *
22   * - Neither the name of the Hewlett-Packard Company nor the name of the
23   * Massachusetts Institute of Technology nor the names of their
24   * contributors may be used to endorse or promote products derived from
25   * this software without specific prior written permission.
26   *
27   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28   * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31   * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
34   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
35   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
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37   * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
38   * DAMAGE.
39   */
40  package org.dspace.app.mediafilter;
41  
42  import java.io.InputStream  ;
43  
44  import org.dspace.content.Bitstream;
45  import org.dspace.content.BitstreamFormat;
46  import org.dspace.content.Bundle;
47  import org.dspace.content.Item;
48  import org.dspace.core.Context;
49  
50  public abstract class MediaFilter
51  {
52      protected Item item = null;
53      
54      /* To create your own filter, implement the following virtual methods */
55  
56      /**
57       * Get a filename for a newly created filtered bitstream
58       * 
59       * @param sourceName
60       *            name of source bitstream
61       * @return filename generated by the filter - for example, document.pdf
62       *         becomes document.pdf.txt
63       */
64      public abstract String   getFilteredName(String   sourceName);
65  
66      /**
67       * @return name of the bundle this filter will stick its generated
68       *         Bitstreams
69       */
70      public abstract String   getBundleName();
71  
72      /**
73       * @return name of the bitstream format (say "HTML" or "Microsoft Word")
74       *         returned by this filter look in the bitstream format registry or
75       *         mediafilter.cfg for valid format strings.
76       */
77      public abstract String   getFormatString();
78  
79      /**
80       * @return string to describe the newly-generated Bitstream's - how it was
81       *         produced is a good idea
82       */
83      public abstract String   getDescription();
84  
85      /**
86       * @param source
87       *            input stream
88       * 
89       * @return result of filter's transformation, written out to a bitstream
90       */
91      public abstract InputStream   getDestinationStream(InputStream   source)
92              throws Exception  ;
93  
94      /* end of methods you need to implement! */
95  
96      /**
97       * processBitstream is a utility class that calls the above virtual methods -
98       * it is unlikely that you will need to override it. It scans the bitstreams
99       * in an item, and decides if a bitstream has already been filtered, and if
100      * not or if overWrite is set, invokes the filter.
101      * 
102      * @param c
103      *            context
104      * @param item
105      *            item containing bitstream to process
106      * @param source
107      *            source bitstream to process
108      * 
109      * @return true if new rendition is created, false if rendition already
110      *         exists and overWrite is not set
111      */
112     public boolean processBitstream(Context c, Item item, Bitstream source)
113             throws Exception  
114     {
115         boolean overWrite = MediaFilterManager.isForce;
116         
117         this.item = item;
118 
119         // get bitstream filename, calculate destination filename
120         String   newName = getFilteredName(source.getName());
121 
122         Bitstream existingBitstream = null; // is there an existing rendition?
123         Bundle targetBundle = null; // bundle we're modifying
124 
125         Bundle[] bundles = item.getBundles(getBundleName());
126 
127         // check if destination bitstream exists
128         if (bundles.length > 0)
129         {
130             // only finds the last match (FIXME?)
131             for (int i = 0; i < bundles.length; i++)
132             {
133                 Bitstream[] bitstreams = bundles[i].getBitstreams();
134 
135                 for (int j = 0; j < bitstreams.length; j++)
136                 {
137                     if (bitstreams[j].getName().equals(newName))
138                     {
139                         targetBundle = bundles[i];
140                         existingBitstream = bitstreams[j];
141                     }
142                 }
143             }
144         }
145 
146         // if exists and overwrite = false, exit
147         if (!overWrite && (existingBitstream != null))
148         {
149             System.out.println("SKIPPED: bitstream " + source.getID()
150                     + " because '" + newName + "' already exists");
151 
152             return false;
153         }
154 
155         InputStream   destStream = getDestinationStream(source.retrieve());
156 
157         // create new bundle if needed
158         if (bundles.length < 1)
159         {
160             targetBundle = item.createBundle(getBundleName());
161         }
162         else
163         {
164             // take the first match
165             targetBundle = bundles[0];
166         }
167 
168         Bitstream b = targetBundle.createBitstream(destStream);
169 
170         // Now set the format and name of the bitstream
171         b.setName(newName);
172         b.setSource("Written by MediaFilter " + this.getClass().getName()); // or
173                                                                             // obj.getClass().getName();
174         b.setDescription(getDescription());
175 
176         // Find the proper format
177         BitstreamFormat bf = BitstreamFormat.findByShortDescription(c,
178                 getFormatString());
179         b.setFormat(bf);
180         b.update();
181 
182         // fixme - set date?
183         // we are overwriting, so remove old bitstream
184         if (existingBitstream != null)
185         {
186             targetBundle.removeBitstream(existingBitstream);
187         }
188 
189         System.out.println("FILTERED: bitstream " + source.getID()
190                 + " and created '" + newName + "'");
191 
192         return true;
193     }
194 }
195
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