/**
* 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.app.oai;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Properties;
import org.apache.log4j.Logger;
import org.dspace.content.Item;
import org.dspace.content.crosswalk.DisseminationCrosswalk;
import org.dspace.core.PluginManager;
import org.dspace.search.HarvestedItemInfo;
import org.jdom.output.XMLOutputter;
import ORG.oclc.oai.server.crosswalk.Crosswalk;
import ORG.oclc.oai.server.verb.CannotDisseminateFormatException;
/**
* An OAICat Crosswalk implementation that calls, in turn, on
* <code>DisseminationCrosswalk</code> plugins.
* It is configured so its "OAI schema label" matches the name of a
* <code>DisseminationCrosswalk</code> plugin. This class
* will then recognize its name and invoke the correct crosswalk
* to produce the results it sends out.
* <p>
* <b>Configuration:</b>
* In the OAICat configuration file (e.g. <code>oaicat.properties</code>
* add a line like this for each plugin crosswalk you wish to provide:
* <pre>
* Crosswalks.<cite>Plugin-Name</cite>=org.dspace.app.oai.PluginCrosswalk
*
* e.g.
*
* Crosswalks.DC=org.dspace.app.oai.PluginCrosswalk
* </pre>
* This creates an OAI metadata prefix "DC" which is implemented
* by the dissemination crosswalk plugin that answers to the name "DC".
* It, in turn, could be found in the DSpace configuration in a line like:
* <pre>
* plugin.named.org.dspace.content.crosswalk.DisseminationCrosswalk = \
* org.dspace.content.crosswalk.SimpleDCDisseminationCrosswalk = DC
* </pre>
*
* <p>
* Note that all OAI crosswalks are instances of this same class, since
* the instance gets bound to a specific <code>DisseminationCrosswalk</code>
* when it is created.
* <p>
* WARNING: This requires at the OAICAT java library version 1.5.38.
* It does NOT work with some older versions.
*
* @author Larry Stone
* @version $Revision$
*/
public class PluginCrosswalk extends Crosswalk
{
/** log4j category */
private static Logger log = Logger.getLogger(PluginCrosswalk.class);
private DisseminationCrosswalk xwalk = null;
// preserve the label from config property for diagnostics.
private String schemaLabel = null;
private static XMLOutputter outputUgly = new XMLOutputter();
/**
* Prepare a "schema location" string for the oaicat Crosswalk
* class's initialization. This is a string consisting of the
* namespace URI, a space, and the schema URL, for the XML
* element to be included in the OAI report. This is not documented
* in oaicat's manuals so we mention it here.
*
* Since this gets called by the constructor, we can't initialize the
* xwalk field so the plugin gets thrown away.
*/
private static String makeSchemaLocation(String schemaLabel)
{
DisseminationCrosswalk xwalk = (DisseminationCrosswalk)
PluginManager.getNamedPlugin(DisseminationCrosswalk.class,
schemaLabel);
if (xwalk != null)
{
String schemaLoc = xwalk.getSchemaLocation();
// initialize the oaicat Crosswalk with a "schemalocation" string,
// which is "{namespace-URI} {schema-URL}" (space separated)
if (schemaLoc != null)
{
log.debug("Initialized schemaLabel="+schemaLabel+" with schemaLocation = \""+schemaLoc+"\"");
return schemaLoc;
}
log.error("makeSchemaLocation: crosswalk cannot provide schemaLocation, label="+schemaLabel);
return "Error No-schemaLocation-for-"+schemaLabel;
}
log.error("No crosswalk found, makeSchemaLocation giving up, label="+schemaLabel);
return "Error No-crosswalk-for-"+schemaLabel;
}
/**
* Constructor; called by
* ORG.oclc.oai.server.crosswalk.Crosswalks, which tries first with
* args (String schemaLabel, Properties properties). This is
* convenient since it lets us use that label to initialize this
* instance of the plugin with the DisseminationCrosswalk crosswalk
* corresponding to that schemaLabel, instead of creating a subclass
* for each one.
* <p>
* WARNING: This requires at the OAICAT java library version 1.5.37.
* It does NOT work with some older versions.
*/
public PluginCrosswalk(String schemaLabel, Properties properties)
{
super(makeSchemaLocation(schemaLabel));
xwalk = (DisseminationCrosswalk)PluginManager.getNamedPlugin(
DisseminationCrosswalk.class, schemaLabel);
this.schemaLabel = schemaLabel;
}
/**
* @return true if this dissemination is available for the item.
*/
public boolean isAvailableFor(Object nativeItem)
{
Item item = ((HarvestedItemInfo) nativeItem).item;
return xwalk.canDisseminate(item);
}
/**
* Do the crosswalk. Returns serialized XML in a string.
*/
public String createMetadata(Object nativeItem)
throws CannotDisseminateFormatException
{
Item item = ((HarvestedItemInfo) nativeItem).item;
try
{
log.debug("OAI plugin, schema="+schemaLabel+", preferList="+String.valueOf(xwalk.preferList()));
if (xwalk.preferList())
{
return outputUgly.outputString(xwalk.disseminateList(item));
}
else
{
return outputUgly.outputString(xwalk.disseminateElement(item));
}
}
catch (Exception e)
{
log.error(this.getClass().getName()+
": hiding exception in CannotDisseminateFormatException:"+
e.toString());
StringWriter sw = new StringWriter();
e.printStackTrace(new PrintWriter(sw));
log.error("*** Stack trace follows:");
log.error(sw.toString());
// Stack loss as exception does not support cause
throw new CannotDisseminateFormatException(schemaLabel);
}
}
}