Metacat

/**

 *  '$RCSfile$'

 *  

 *  Copyright: 2016 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Jing Tao

 * 

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

package edu.ucsb.nceas.metacat.service;

import java.io.IOException;

import java.io.Reader;

import org.apache.log4j.Logger;

import org.xml.sax.Attributes;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.DefaultHandler;

import org.xml.sax.helpers.XMLReaderFactory;

import edu.ucsb.nceas.metacat.properties.PropertyService;

import edu.ucsb.nceas.utilities.PropertyNotFoundException;

/**

 * This class will parse the root element to figure out the namespace of the root element(we also call

 * it the namespace of the element). If it doesn't have a namespace, but it does have an attribute of noNamespaceSchemaLocation

 * at the root element, it will get the value as well. 

 * @author tao

 *

 */

public class XMLNamespaceParser extends DefaultHandler {

    private Reader xml = null;

    private XMLReader parser = null;

    private boolean rootElement = true;

    private static Logger logMetacat = Logger.getLogger(XMLNamespaceParser.class);

    private String namespace = null;

    private String noNamespaceSchemaLocation = null;

    /**

     * Constructor

     * @param xml the xml object which will be parsed

     */

    public XMLNamespaceParser(Reader xml) throws SAXException, PropertyNotFoundException {

      this.xml = xml;

      initParser();

    }

    /*

     * Initialize sax parser

     */

    private void initParser() throws SAXException, PropertyNotFoundException {   

      // Get an instance of the parser

       String parserName = PropertyService.getProperty("xml.saxparser");

       parser = XMLReaderFactory.createXMLReader(parserName);

       parser.setContentHandler(this);

    }

    /**

     * Parse the xml file

     * @throws SAXException if some sax related exception happens

     * @throws IOException if the schema content couldn't be found

     */

    public void parse() throws SAXException, IOException {

        try {

            parser.parse(new InputSource(xml));

        } catch (ParsingEndException e) {

            logMetacat.debug("XMLNamespace.parse - The parsing process stopped.");

        }

    }

    /** SAX Handler that is called at the start of each XML element */

    @Override

    public void startElement(String uri, String localName, String qName,

            Attributes atts) throws SAXException{

      logMetacat.debug("XMLNamespace.startElement - uri: "+uri);

      logMetacat.debug("XMLNamespace.startElement - local name: "+localName);

      logMetacat.debug("XMLNamespace.startElement - qualified name: "+qName);

      if(!rootElement) {

          throw new ParsingEndException("We only parse the root elment. We got there and the parsing stopped.");

      } else {

          rootElement = false;

          if(uri != null && !uri.trim().equals("")) {

              namespace = uri;

          }

          logMetacat.debug("XMLNamespace.startElement - the namespace is: "+namespace);

          if(atts != null) {

              for(int i=0; i<atts.getLength(); i++) {

                  if((atts.getURI(i) != null && atts.getURI(i).equals("http://www.w3.org/2001/XMLSchema-instance")) &&

                          (atts.getLocalName(i) != null && atts.getLocalName(i).equals("noNamespaceSchemaLocation"))) {

                      if(atts.getValue(i) != null && !atts.getValue(i).trim().equals("")) {

                          noNamespaceSchemaLocation = atts.getValue(i);

                      }

                      logMetacat.debug("XMLNamespace.startElement - we found the attribute of the noNamespaceSchemaLocation and its value is: "+noNamespaceSchemaLocation);

                      break;

                  }

              }

          }

      }

    }

    /**

     * Get the namespace of the document (root element). The parse() method should be called first

     * @return the value of the namespace. A null will be returned if it can't be found.

     */

    public String getNamespace() {

        logMetacat.debug("XMLNamespace.getNamespace - the namespace is: "+namespace);

        return namespace;

    }

    /**

     * Get the value of noNamespaceSchemaLocation of the document (root element). The parse() method should be called first

     * @return the value of the noNamespaceSchemaLocation. A null will be returned if it can't be found.

     */

    public String getNoNamespaceSchemaLocation() {

        logMetacat.debug("XMLNamespace.getNoNamespaceSchemaLocation - the NoNamespaceSchemaLocation is: "+noNamespaceSchemaLocation);

        return noNamespaceSchemaLocation;

    }

    /**

     * A class signals that the parsing process stop early. 

     * @author tao

     *

     */

    class ParsingEndException extends RuntimeException {

        public ParsingEndException(String message) {

            super(message);

        }

    }

}