Metacat

/**

 * Copyright 2006 OCLC Online Computer Library Center Licensed under the Apache

 * License, Version 2.0 (the "License"); you may not use this file except in

 * compliance with the License. You may obtain a copy of the License at

 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or

 * agreed to in writing, software distributed under the License is distributed on

 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

 * or implied. See the License for the specific language governing permissions and

 * limitations under the License.

 */

package edu.ucsb.nceas.metacat.oaipmh.provider.server.crosswalk;

import java.io.FileInputStream;

import java.io.StringReader;

import java.io.StringWriter;

import java.util.HashMap;

import java.util.Properties;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.stream.StreamResult;

import javax.xml.transform.stream.StreamSource;

import org.apache.log4j.Logger;

import ORG.oclc.oai.server.crosswalk.Crosswalk;

import ORG.oclc.oai.server.verb.CannotDisseminateFormatException;

import ORG.oclc.oai.server.verb.OAIInternalServerError;

/**

 * Provides EML documents in eml-2.1.0 format. For eml-2.1.0 documents, we

 * simply return the metadata that was read from Metacat. For eml-2.0.x

 * documents, we use the EML Utilities stylesheet to transform the document

 * to eml-2.1.0.

 */

public class Eml extends Crosswalk {

  /* Class fields */

  private static final Logger logger = Logger.getLogger(Eml.class);

  private static String dirPath = null;

  // This is a local copy of the stylesheet from the EML Utilities module

  private static final String XSLT_NAME = "eml201to210.xsl";

  private static final String SCHEMA_LOCATION =

    "eml://ecoinformatics.org/eml-2.1.0 " +

    "http://knb.ecoinformatics.org/knb/schema/eml-2.1.0/eml.xsd";

  /* Instance fields */

  private Transformer transformer = null;

  /* Constructors */

  /**

   * The constructor assigns the schemaLocation associated with this crosswalk.

   * Since the crosswalk is trivial in this case, no properties are utilized.

   * 

   * @param properties

   *          properties that are needed to configure the crosswalk.

   */

  public Eml(Properties properties) throws OAIInternalServerError {

    super(SCHEMA_LOCATION);

    String xsltPath = dirPath + "/" + XSLT_NAME;

    try {

      TransformerFactory tFactory = TransformerFactory.newInstance();

      FileInputStream fileInputStream = new FileInputStream(xsltPath);

      StreamSource xslSource = new StreamSource(fileInputStream);

      this.transformer = tFactory.newTransformer(xslSource);

    } 

    catch (Exception e) {

      e.printStackTrace();

      throw new OAIInternalServerError(e.getMessage());

    }

  }

  /* Class methods */

  /**

   * Set the value of the configuration directory path so that XSLT stylesheets

   * can be located on the system.

   * 

   * @param configDir   the configuration directory path

   */

  public static void setDirPath(String configDir) {

    Eml.dirPath = configDir;

  }

  /* Instance methods */

  /**

   * Perform the actual crosswalk.

   * 

   * @param nativeItem  A HashMap object that contains the EML string that was

   *                    retrieved from Metacat and stored as the value of the

   *                    "recordBytes" key

   * @return eml210doc  a String containing the metadata to be stored within 

   *                    the <metadata> element in eml 2.1.0 format

   * @exception CannotDisseminateFormatException

   *              nativeItem doesn't support this format.

   */

  public String createMetadata(Object nativeItem)

      throws CannotDisseminateFormatException {

    HashMap recordMap = (HashMap) nativeItem;

    String eml210doc = null;

    String docid = (String) recordMap.get("localIdentifier");

    String doctype = (String) recordMap.get("doctype");

    String xmlRec = (String) recordMap.get("recordBytes");

    /* Transform eml-2.0.x documents to eml-2.1.0 using the stylesheet from

     * the EML Utilities module 

     */

    if ((doctype != null) && (doctype.contains("eml-2.0.0") ||

                              doctype.contains("eml-2.0.1")

                             )

       ) 

    {

      if (docid != null) {

        logger.debug("Transforming " + doctype + " document, " + docid + ", to eml-2.1.0.");

      }

      try {

        StringReader stringReader = new StringReader(xmlRec);

        StreamSource streamSource = new StreamSource(stringReader);

        StringWriter stringWriter = new StringWriter();

        synchronized (transformer) {

          transformer.transform(streamSource, new StreamResult(stringWriter));

        }

        eml210doc = stringWriter.toString();

      } 

      catch (Exception e) {

        throw new CannotDisseminateFormatException(e.getMessage());

      }

    }

    else if (xmlRec.contains("eml://ecoinformatics.org/eml-2.1.0")) {

        eml210doc = xmlRec;

    }

    eml210doc = eml210doc.trim();

    /*

     * Remove the lead xml processing instruction because the document is going

     * to be placed inside an OAI <metadata> element within a 

     */

    if (eml210doc.startsWith("<?")) {

      int offset = eml210doc.indexOf("?>");

      eml210doc = eml210doc.substring(offset + 2);

    }

    return eml210doc;

  }

  /**

   * Can this nativeItem be represented in 'eml' format?

   * 

   * @param nativeItem              a record in native format

   * @return true if 'eml' format is possible, false otherwise.

   */

  public boolean isAvailableFor(Object nativeItem) {

    // We assume that all EML documents can be represented in eml format

    return true;

  }

}