/**
* The contents of this file are subject to the license and copyright
* detailed in the LICENSE and NOTICE files at the root of the source
* tree and available online at
*
* http://www.dspace.org/license/
*/
package org.dspace.content.crosswalk;
import java.io.File;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import org.apache.log4j.Logger;
import org.dspace.core.ConfigurationManager;
import org.dspace.core.SelfNamedPlugin;
import org.jdom.Namespace;
import org.jdom.transform.XSLTransformException;
import org.jdom.transform.XSLTransformer;
/**
* Configurable XSLT-driven Crosswalk
* <p>
* This is the superclass of the XSLT dissemination and submission crosswalks.
* These classes let you can create many different crosswalks between
* DSpace internal data and any XML without changing any code, just
* XSL transformation (XSLT) stylesheets.
* Each configured stylesheet appears as a new plugin name, although they all
* share the same plugin implementation class.
* <p>
* The XML transformation must produce (for submission) or expect (for
* dissemination) a document in DIM - DSpace Intermediate Metadata format.
* See <a href="http://wiki.dspace.org/DspaceIntermediateMetadata">
* http://wiki.dspace.org/DspaceIntermediateMetadata</a> for details.
* <h3>Configuration</h3>
* Prepare your DSpace configuration as follows:
* <p>
* A submission crosswalk is described by a
* configuration key like
* <pre> crosswalk.submission.<i>PluginName</i>.stylesheet = <i>path</i></pre>
* The <em>alias</em> names the Plugin name,
* and the <em>path</em> value is the pathname (relative to <code><em>dspace.dir</em>/config</code>)
* of the crosswalk stylesheet, e.g. <code>"mycrosswalk.xslt"</code>
* <p>
* For example, this configures a crosswalk named "LOM" using a stylesheet
* in <code>config/crosswalks/d-lom.xsl</code> under the DSpace "home" directory:
* <pre> crosswalk.submission.stylesheet.LOM = crosswalks/d-lom.xsl</pre>
* <p>
* A dissemination crosswalk is described by a
* configuration key like
* <pre> crosswalk.dissemination.<i>PluginName</i>.stylesheet = <i>path</i></pre>
The <em>alias</em> names the Plugin name,
* and the <em>path</em> value is the pathname (relative to <code><em>dspace.dir</em>/config</code>)
* of the crosswalk stylesheet, e.g. <code>"mycrosswalk.xslt"</code>
* <p>
* You can have two names point to the same crosswalk,
* just add two configuration entries with the same path, e.g.
* <pre>
* crosswalk.submission.MyFormat.stylesheet = crosswalks/myformat.xslt
* crosswalk.submission.almost_DC.stylesheet = crosswalks/myformat.xslt
* </pre>
* <p>
* NOTE: This plugin will automatically reload any XSL stylesheet that
* was modified since it was last loaded. This lets you edit and test
* stylesheets without restarting DSpace.
* <p>
* You must use the <code>PluginManager</code> to instantiate an
* XSLT crosswalk plugin, e.g.
* <pre> IngestionCrosswalk xwalk = PluginManager.getPlugin(IngestionCrosswalk.class, "LOM");</pre>
* <p>
* Since there is significant overhead in reading the properties file to
* configure the crosswalk, and a crosswalk instance may be used any number
* of times, we recommend caching one instance of the crosswalk for each
* alias and simply reusing those instances. The <code>PluginManager</code>
* does this automatically.
*
* @author Larry Stone
* @version $Revision$
*/
public abstract class XSLTCrosswalk extends SelfNamedPlugin
{
/** log4j category */
private static Logger log = Logger.getLogger(XSLTCrosswalk.class);
/**
* DSpace XML Namespace in JDOM form.
*/
public static final Namespace DIM_NS =
Namespace.getNamespace("dim", "http://www.dspace.org/xmlns/dspace/dim");
/** Prefix for all lines in the config file for XSLT plugins. */
protected static final String CONFIG_PREFIX = "crosswalk.";
private static final String CONFIG_STYLESHEET = ".stylesheet";
/**
* Derive list of plugin name from DSpace configuration entries
* for crosswalks. The <em>direction</em> parameter should be either
* "dissemination" or "submission", so it looks for keys like
* <code>crosswalk.submission.{NAME}.stylesheet</code>
*/
protected static String[] makeAliases(String direction)
{
String prefix = CONFIG_PREFIX+direction+".";
String suffix = CONFIG_STYLESHEET;
List<String> aliasList = new ArrayList<String>();
Enumeration<String> pe = (Enumeration<String>)ConfigurationManager.propertyNames();
log.debug("XSLTCrosswalk: Looking for config prefix = "+prefix);
while (pe.hasMoreElements())
{
String key = pe.nextElement();
if (key.startsWith(prefix) && key.endsWith(suffix))
{
log.debug("Getting XSLT plugin name from config line: "+key);
aliasList.add(key.substring(prefix.length(), key.length()-suffix.length()));
}
}
return aliasList.toArray(new String[aliasList.size()]);
}
private XSLTransformer transformer = null;
private File transformerFile = null;
private long transformerLastModified = 0;
/**
* Initialize the Transformation stylesheet from configured stylesheet file.
* @param direction the direction of xwalk, either "submission" or
* "dissemination"
* @return transformer or null if there was error initializing.
*/
protected XSLTransformer getTransformer(String direction)
{
if (transformerFile == null)
{
String myAlias = getPluginInstanceName();
if (myAlias == null)
{
log.error("Must use PluginManager to instantiate XSLTCrosswalk so the class knows its name.");
return null;
}
String cmPropName = CONFIG_PREFIX+direction+"."+myAlias+CONFIG_STYLESHEET;
String fname = ConfigurationManager.getProperty(cmPropName);
if (fname == null)
{
log.error("Missing configuration filename for XSLT-based crosswalk: no "+
"value for property = "+cmPropName);
return null;
}
else
{
String parent = ConfigurationManager.getProperty("dspace.dir") +
File.separator + "config" + File.separator;
transformerFile = new File(parent, fname);
}
}
// load if first time, or reload if stylesheet changed:
if (transformer == null ||
transformerFile.lastModified() > transformerLastModified)
{
try
{
log.debug((transformer == null ? "Loading " : "Reloading")+
getPluginInstanceName()+" XSLT stylesheet from "+transformerFile.toString());
transformer = new XSLTransformer(transformerFile);
transformerLastModified = transformerFile.lastModified();
}
catch (XSLTransformException e)
{
log.error("Failed to initialize XSLTCrosswalk("+getPluginInstanceName()+"):"+e.toString());
}
}
return transformer;
}
}