PluginCrosswalk


1   /*
2    * PluginCrosswalk.java
3    *
4    * Version: $Revision: 1.2 $
5    *
6    * Date: $Date: 2006/03/17 00:04:39 $
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.
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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
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40  package org.dspace.app.oai;
41  
42  import java.util.Properties  ;
43  import java.io.StringWriter  ;
44  import java.io.PrintWriter  ;
45  
46  import org.dspace.content.Item;
47  import org.dspace.core.PluginManager;
48  import org.dspace.search.HarvestedItemInfo;
49  import org.dspace.content.crosswalk.DisseminationCrosswalk;
50  
51  import org.apache.log4j.Logger;
52  
53  import ORG.oclc.oai.server.crosswalk.Crosswalk;
54  import ORG.oclc.oai.server.verb.CannotDisseminateFormatException;
55  
56  import org.jdom.*;
57  import org.jdom.output.XMLOutputter;
58  import org.jdom.output.Format;
59  
60  /**
61   * An OAICat Crosswalk implementation that calls, in turn, on
62   * <code>DisseminationCrosswalk</code> plugins.
63   * It is configured so its "OAI schema label" matches the name of a
64   * <code>DisseminationCrosswalk</code> plugin.  This class
65   * will then recognize its name and invoke the correct crosswalk
66   * to produce the results it sends out.
67   * <p>
68   * <b>Configuration:</b>
69   * In the OAICat configuration file (e.g. <code>oaicat.properties</code>
70   * add a line like this for each plugin crosswalk you wish to provide:
71   * <pre>
72   *   Crosswalks.<cite>Plugin-Name</cite>=org.dspace.app.oai.PluginCrosswalk
73   *
74   *    e.g.
75   *
76   *   Crosswalks.DC=org.dspace.app.oai.PluginCrosswalk
77   * </pre>
78   * This creates an OAI metadata prefix "DC" which is implemented
79   * by the dissemination crosswalk plugin that answers to the name "DC".
80   * It, in turn, could be found in the DSpace configuration in a line like:
81   * <pre>
82   *  plugin.named.org.dspace.content.crosswalk.DisseminationCrosswalk = \
83   *    org.dspace.content.crosswalk.SimpleDCDisseminationCrosswalk = DC
84   * </pre>
85   *
86   * <p>
87   * Note that all OAI crosswalks are instances of this same class, since
88   * the instance gets bound to a specific <code>DisseminationCrosswalk</code>
89   * when it is created.
90   * <p>
91   *  WARNING: This requires at the OAICAT java library version 1.5.38.
92   *    It does NOT work with some older versions.
93   *
94   * @author Larry Stone
95   * @version $Revision: 1.2 $
96   */
97  public class PluginCrosswalk extends Crosswalk
98  {
99      /** log4j category */
100     private static Logger log = Logger.getLogger(PluginCrosswalk.class);
101 
102     private DisseminationCrosswalk xwalk = null;
103 
104     // preserve the label from config property for diagnostics.
105     private String   schemaLabel = null;
106 
107     private static XMLOutputter outputUgly = new XMLOutputter();
108 
109     /**
110      * Prepare a "schema location" string for the oaicat Crosswalk
111      * class's initialization.  This is a string consisting of the
112      * namespace URI, a space, and the schema URL, for the XML
113      * element to be included in the OAI report.  This is not documented
114      * in oaicat's manuals so we mention it here.
115      *
116      * Since this gets called by the constructor, we can't initialize the
117      * xwalk field so the plugin gets thrown away.
118      */
119     private static String   makeSchemaLocation(String   schemaLabel)
120     {
121         DisseminationCrosswalk xwalk = (DisseminationCrosswalk)
122                     PluginManager.getNamedPlugin(DisseminationCrosswalk.class,
123                                                  schemaLabel);
124         if (xwalk != null)
125         {
126             String   schemaLoc = xwalk.getSchemaLocation();
127 
128             // initialize the oaicat Crosswalk with a "schemalocation" string,
129             // which is "{namespace-URI} {schema-URL}"  (space separated)
130             if (schemaLoc != null)
131             {
132                 log.debug("Initialized schemaLabel="+schemaLabel+" with schemaLocation = \""+schemaLoc+"\"");
133                 return schemaLoc;
134             }
135             log.error("makeSchemaLocation:  crosswalk cannot provide schemaLocation, label="+schemaLabel);
136             return "Error No-schemaLocation-for-"+schemaLabel;
137         }
138         log.error("No crosswalk found, makeSchemaLocation giving up, label="+schemaLabel);
139         return "Error No-crosswalk-for-"+schemaLabel;
140     }
141 
142     /**
143      * Constructor; called by
144      * ORG.oclc.oai.server.crosswalk.Crosswalks, which tries first with
145      * args (String schemaLabel, Properties properties).  This is
146      * convenient since it lets us use that label to initialize this
147      * instance of the plugin with the DisseminationCrosswalk crosswalk
148      * corresponding to that schemaLabel, instead of creating a subclass
149      * for each one.
150      * <p>
151      *  WARNING: This requires at the OAICAT java library version 1.5.37.
152      *    It does NOT work with some older versions.
153      */
154     public PluginCrosswalk(String   schemaLabel, Properties   properties)
155     {
156         super(makeSchemaLocation(schemaLabel));
157         xwalk = (DisseminationCrosswalk)PluginManager.getNamedPlugin(
158                     DisseminationCrosswalk.class, schemaLabel);
159         this.schemaLabel = schemaLabel;
160     }
161 
162     /**
163      * @return true if this dissemination is available for the item.
164      */
165     public boolean isAvailableFor(Object   nativeItem)
166     {
167         Item item = ((HarvestedItemInfo) nativeItem).item;
168         return xwalk.canDisseminate(item);
169     }
170 
171     /**
172      * Do the crosswalk.  Returns serialized XML in a string.
173      */
174     public String   createMetadata(Object   nativeItem)
175             throws CannotDisseminateFormatException
176     {
177         Item item = ((HarvestedItemInfo) nativeItem).item;
178         try
179         {
180             log.debug("OAI plugin, schema="+schemaLabel+", preferList="+String.valueOf(xwalk.preferList()));
181             if (xwalk.preferList())
182                 return outputUgly.outputString(xwalk.disseminateList(item));
183             else
184                 return outputUgly.outputString(xwalk.disseminateElement(item));
185         }
186         catch (Exception   e)
187         {
188             log.error(this.getClass().getName()+
189                     ": hiding exception in CannotDisseminateFormatException:"+
190                     e.toString());
191 
192                 StringWriter   sw = new StringWriter  ();
193                 e.printStackTrace(new PrintWriter  (sw));
194                 log.error("*** Stack trace follows:");
195                 log.error(sw.toString());
196 
197             throw new CannotDisseminateFormatException(schemaLabel);
198         }
199     }
200 }
201
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