validation.xslt.handler.XsltResultHandler.java Source code

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Here is the source code for validation.xslt.handler.XsltResultHandler.java

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package validation.xslt.handler;

import messages.SnannySostServerException;
import messages.SnannySostServerMessages;
import java.io.IOException;
import java.io.StringReader;
import javax.ws.rs.core.Response.Status;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/** Manage XSLT results for schematron validation via XSL.
 * This class is also a SAX handler for extracting the validation errors,
 * the analyse method is synchronized, because SAX parsing is not thread safe and
 * The sos server is a servlet which uses threads
 * @author mlarour
 */
public class XsltResultHandler extends DefaultHandler {
    private static SAXParser parser;
    private static StringBuilder buffer;

    // xml tags
    private static String FAILED = "svrl:failed-assert";
    private boolean failed;

    public static String NORMAL_STATUS = "OK";

    // singleton
    private static XsltResultHandler xsltResultHandler = null;

    /** Singleton getter.
     * 
     * @return the unique instance
     */
    public static synchronized XsltResultHandler singleton() {
        if (xsltResultHandler == null) {
            xsltResultHandler = new XsltResultHandler();
        }
        return (xsltResultHandler);
    }

    /** private constructor, this class is a singleton.
     * 
     */
    private XsltResultHandler() {
        super();
        buffer = new StringBuilder();
        try {
            parser = SAXParserFactory.newInstance().newSAXParser();
        } catch (ParserConfigurationException | SAXException ex) {
            throw new SnannySostServerException(SnannySostServerMessages.ERROR_SAXPARSER_XSLT,
                    Status.SERVICE_UNAVAILABLE);
        }
    }

    /** initialization before a next sax parsing
     * 
     */
    private void reset() {
        buffer.delete(0, buffer.length());
        failed = false;
    }

    /** Extract errors from xml resulting of schematron validation via xslt.
     * 
     * @param xsltResult xml resulting of schematron validation via xslt
     * @return null if xml is schematron valid, errors elsewhere
     */
    public synchronized String analyse(String xsltResult) {
        try {
            InputSource is = new InputSource(new StringReader(xsltResult));
            xsltResultHandler.reset();
            parser.parse(is, xsltResultHandler);
        } catch (SAXException ex) {
            if (ex.getMessage().compareTo(NORMAL_STATUS) == 0) {
                return (buffer.toString());
            }
            throw new SnannySostServerException(SnannySostServerMessages.ERROR_PARSE_XSLT, Status.BAD_REQUEST);
        } catch (IOException ex) {
            throw new SnannySostServerException(SnannySostServerMessages.ERROR_IO_XSLT, Status.SERVICE_UNAVAILABLE);
        }
        return (null);
    }

    /** SAX handling, Receive notification of the start of an element. 
     * 
     * @param namespaceURI The Namespace URI, or the empty string if the element has no Namespace URI or if Namespace processing is not being performed.
     * @param localName The local name (without prefix), or the empty string if Namespace processing is not being performed.
     * @param qName The qualified name (with prefix), or the empty string if qualified names are not available.
     * @param atts The attributes attached to the element. If there are no attributes, it shall be an empty Attributes object.
     * @throws SAXException Any SAX exception, possibly wrapping another exception.
     */
    @Override
    public void startElement(String namespaceURI, String localName, String qName, Attributes atts)
            throws SAXException {
        if (qName.compareTo(FAILED) == 0) {
            failed = true;
            buffer.append("<");
            buffer.append(qName);
            for (int i = 0; i < atts.getLength(); i++) {
                buffer.append(" ");
                buffer.append(atts.getQName(i));
                buffer.append("=\"");
                buffer.append(org.json.XML.escape(atts.getValue(i)));
                buffer.append("\"");
            }
            buffer.append('>');
        }
    }

    /** SAX handling, Receive notification of character data inside an element. 
     * 
     * @param ch The characters.
     * @param start The start position in the character array.
     * @param length The number of characters to use from the character array.
     * @throws SAXException Any SAX exception, possibly wrapping another exception.
     */
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        if (failed) {
            buffer.append(ch, start, length);
        }
    }

    /** SAX handling, Receive notification of the end of an element.
     * 
     * @param namespaceURI The Namespace URI, or the empty string if the element has no Namespace URI or if Namespace processing is not being performed.
     * @param localName The local name (without prefix), or the empty string if Namespace processing is not being performed.
     * @param qName The qualified name (with prefix), or the empty string if qualified names are not available.
     * @throws SAXException Any SAX exception, possibly wrapping another exception.
     */
    @Override
    public void endElement(String namespaceURI, String localName, String qName) throws SAXException {
        if (qName.compareTo(FAILED) == 0) {
            if (failed) {
                buffer.append("</");
                buffer.append(qName);
                buffer.append(">");
                throw new SAXException(NORMAL_STATUS);
            }
        }
    }

}