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tao
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/**
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* '$RCSfile$'
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*
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* Copyright: 2016 Regents of the University of California and the
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* National Center for Ecological Analysis and Synthesis
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* Authors: Jing Tao
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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package edu.ucsb.nceas.metacat.service;
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import java.io.IOException;
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import java.io.Reader;
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import org.apache.log4j.Logger;
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import org.xml.sax.Attributes;
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import org.xml.sax.InputSource;
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import org.xml.sax.SAXException;
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import org.xml.sax.XMLReader;
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import org.xml.sax.helpers.DefaultHandler;
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import org.xml.sax.helpers.XMLReaderFactory;
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import edu.ucsb.nceas.metacat.properties.PropertyService;
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import edu.ucsb.nceas.utilities.PropertyNotFoundException;
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/**
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* This class will parse the root element to figure out the namespace of the root element(we also call
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* it the namespace of the element). If it doesn't have a namespace, but it does have an attribute of noNamespaceSchemaLocation
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* at the root element, it will get the value as well.
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* @author tao
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*
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*/
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public class XMLNamespaceParser extends DefaultHandler {
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private Reader xml = null;
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private XMLReader parser = null;
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private boolean rootElement = true;
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private static Logger logMetacat = Logger.getLogger(XMLNamespaceParser.class);
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private String namespace = null;
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private String noNamespaceSchemaLocation = null;
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/**
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* Constructor
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* @param xml the xml object which will be parsed
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*/
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public XMLNamespaceParser(Reader xml) throws SAXException, PropertyNotFoundException {
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this.xml = xml;
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initParser();
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}
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/*
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* Initialize sax parser
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*/
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private void initParser() throws SAXException, PropertyNotFoundException {
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// Get an instance of the parser
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String parserName = PropertyService.getProperty("xml.saxparser");
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parser = XMLReaderFactory.createXMLReader(parserName);
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parser.setContentHandler(this);
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}
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/**
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* Parse the xml file
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* @throws SAXException if some sax related exception happens
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* @throws IOException if the schema content couldn't be found
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*/
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public void parse() throws SAXException, IOException {
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try {
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parser.parse(new InputSource(xml));
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} catch (ParsingEndException e) {
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logMetacat.debug("XMLNamespace.parse - The parsing process stopped.");
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}
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}
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/** SAX Handler that is called at the start of each XML element */
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@Override
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public void startElement(String uri, String localName, String qName,
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Attributes atts) throws SAXException{
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logMetacat.debug("XMLNamespace.startElement - uri: "+uri);
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logMetacat.debug("XMLNamespace.startElement - local name: "+localName);
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logMetacat.debug("XMLNamespace.startElement - qualified name: "+qName);
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if(!rootElement) {
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throw new ParsingEndException("We only parse the root elment. We got there and the parsing stopped.");
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} else {
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rootElement = false;
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if(uri != null && !uri.trim().equals("")) {
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namespace = uri;
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}
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logMetacat.debug("XMLNamespace.startElement - the namespace is: "+namespace);
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if(atts != null) {
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for(int i=0; i<atts.getLength(); i++) {
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if((atts.getURI(i) != null && atts.getURI(i).equals("http://www.w3.org/2001/XMLSchema-instance")) &&
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(atts.getLocalName(i) != null && atts.getLocalName(i).equals("noNamespaceSchemaLocation"))) {
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if(atts.getValue(i) != null && !atts.getValue(i).trim().equals("")) {
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noNamespaceSchemaLocation = atts.getValue(i);
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}
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logMetacat.debug("XMLNamespace.startElement - we found the attribute of the noNamespaceSchemaLocation and its value is: "+noNamespaceSchemaLocation);
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break;
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}
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}
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}
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}
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}
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/**
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* Get the namespace of the document (root element). The parse() method should be called first
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* @return the value of the namespace. A null will be returned if it can't be found.
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*/
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public String getNamespace() {
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logMetacat.debug("XMLNamespace.getNamespace - the namespace is: "+namespace);
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return namespace;
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}
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/**
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* Get the value of noNamespaceSchemaLocation of the document (root element). The parse() method should be called first
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* @return the value of the noNamespaceSchemaLocation. A null will be returned if it can't be found.
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*/
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public String getNoNamespaceSchemaLocation() {
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logMetacat.debug("XMLNamespace.getNoNamespaceSchemaLocation - the NoNamespaceSchemaLocation is: "+noNamespaceSchemaLocation);
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return noNamespaceSchemaLocation;
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}
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/**
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* A class signals that the parsing process stop early.
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* @author tao
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*
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*/
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class ParsingEndException extends RuntimeException {
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public ParsingEndException(String message) {
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super(message);
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}
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}
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}
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