source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/util/XMLConverter.java@ 24393

/*
 *    XMLConverter.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3.util;

// XML classes
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document; 
import org.w3c.dom.DocumentType; 
import org.w3c.dom.Element; 
import org.w3c.dom.Node; 
import org.w3c.dom.NodeList;
import org.w3c.dom.NamedNodeMap;
import org.xml.sax.InputSource;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXParseException;
import org.apache.xerces.parsers.DOMParser;
import org.apache.xerces.dom.*; // for new Documents

// other java classes
import java.io.Reader;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.util.regex.*;

import org.apache.log4j.*;

// Apache Commons
import org.apache.commons.lang3.*;

import java.util.*;
import java.lang.reflect.*;

/** XMLConverter - utility class for greenstone
 *
 * parses XML Strings into Documents, converts Nodes to Strings
 * different parsers have different behaviour - can experiment in here
 * now we only use xerces
 *
 */
public class XMLConverter {

     static Logger logger = Logger.getLogger(org.greenstone.gsdl3.util.XMLConverter.class.getName());

    /** xerces parser */
    protected DOMParser parser = null;

    private static boolean outputEscaping = true;

     /** the no-args constructor */
    public XMLConverter() {
    try {
        this.parser = new DOMParser();
        this.parser.setFeature("http://xml.org/sax/features/validation", false);
        // don't try and load external DTD - no need if we are not validating, and may cause connection errors if a proxy is not set up.
        this.parser.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
        // a performance test showed that having this on lead to increased 
        // memory use for small-medium docs, and not much gain for large 
        // docs.
        // http://www.sosnoski.com/opensrc/xmlbench/conclusions.html
        this.parser.setFeature("http://apache.org/xml/features/dom/defer-node-expansion", false);
        // add an errorhandler to the parser which will store useful a error message on encountering fatal errors, errors and warnings when parsing
        // this errormessage can then be converted to xhtml and displayed in a browser.
        this.parser.setErrorHandler(new ParseErrorHandler());
    } catch (Exception e) {
        logger.error(e.getMessage());
    }
    }

    /** sets the entity resolver. pass in null to unset it */
    public void setEntityResolver(EntityResolver er) {
    this.parser.setEntityResolver(er);
    }

    /** Given a Node representing an Element or Document, will return the 
     * Element/docroot Element. Returns null if the Node was not an element. */
    public static Element nodeToElement(Node node)
    {
    if(node == null) {
        return null;
    }
    short nodeType = node.getNodeType();

    if (nodeType == Node.DOCUMENT_NODE) {
        Document docNode = (Document)node;
        return docNode.getDocumentElement() ;
    }
    else if (nodeType == Node.ELEMENT_NODE) {
        return (Element)node;
    }
    else {
        String message = "Expecting Document or Element node type but got " 
        + node.getNodeName() + "\nReturning null";
        System.err.println(message);
        logger.warn(message);
        return null;
    }
    }

    /** returns a DOM Document */
    public Document getDOM(String in) {
        
    try {
        Reader reader = new StringReader(in);
        InputSource xml_source = new InputSource(reader);
        
        this.parser.parse(xml_source);
        Document doc = this.parser.getDocument();
        
        return doc;
        
    } catch (Exception e) {
        logger.error(e.getMessage());
    }
    return null;
    }
  
    /** returns a DOM Document */
    public Document getDOM(File in) {
    try {
        FileReader reader = new FileReader(in);
        InputSource xml_source = new InputSource(reader);
        this.parser.parse(xml_source);
        Document doc = this.parser.getDocument();
        return doc;

    } catch (Exception e) {
        logger.error(e.getMessage(), e);
        
    }
    return null;
    }

    /** returns a DOM document */
    public Document getDOM(File in, String encoding) {
    try {
        
        InputStreamReader isr = new InputStreamReader(new FileInputStream(in), encoding);
        InputSource xml_source = new InputSource(isr);
        
        this.parser.parse(xml_source);
        Document doc = this.parser.getDocument();
        
        return doc;

    } catch (Exception e) {
        logger.error(e.getMessage());
    }
    return null;
    }
    

    /** creates a new empty DOM Document */
    public static Document newDOM() {
    Document doc = new DocumentImpl(); 
    return doc;
    }
    
    /**
     * This method's parameters represent the parts of the Doctype of this
     * Document that is to be created.
     * For more info see 
     * http://xerces.apache.org/xerces-j/apiDocs/org/apache/xerces/dom/DocumentTypeImpl.html#DocumentTypeImpl(org.apache.xerces.dom.CoreDocumentImpl,%20java.lang.String)
     * 
     * */
    public static Document newDOM(String qualifiedName, String publicID, String systemID) {
        // create empty DOM document
        DocumentImpl docImpl = new DocumentImpl(); 
        
        // Need to use the document to create the docType for it
        DocumentType myDocType = new DocumentTypeImpl(docImpl, qualifiedName, publicID, systemID);
        
        // Although we have created the docType using the document, we need to still 
        // put it into the empty document we just created 
        try{
            docImpl.appendChild(myDocType);
        } catch(Exception e) {
            System.out.println("Could not append docType because: " + e) ;      
        }
        
        // return the document containing a DocType
        return docImpl;     
    }

    /** returns the Node as a String */
    public static String getString(Node xmlNode)
    {
    outputEscaping = true;
    StringBuffer xmlRepresentation = new StringBuffer();
    getString(xmlNode, xmlRepresentation, 0, false);
    return xmlRepresentation.toString();
    }

    /** returns the node as a nicely formatted String - this introduces extra
     * text nodes if the String is read back in as a DOM, so should only be 
     * used for printing */
    public static String getPrettyString(Node xmlNode) {
    
    outputEscaping = true;
    StringBuffer xmlRepresentation = new StringBuffer();
    getString(xmlNode, xmlRepresentation, 0, true);
    return xmlRepresentation.toString();
    }

    /* For the purposes of logger.debug statements, where this is called and hence outputted,
    returns an empty string if debugging is not enabled */
    public static String getPrettyStringLogger(Node xmlNode, Logger log) {

    if(log.isDebugEnabled())
        return getPrettyString(xmlNode);
    
    return "";

    }

    private static void getString(Node xmlNode, StringBuffer xmlRepresentation, 
                 int depth, boolean pretty)
    {
    
    if (xmlNode == null) {
        xmlRepresentation.append("<null>");
        return;
    }

    short nodeType = xmlNode.getNodeType();
    String nodeName = xmlNode.getNodeName();

    if (nodeType == Node.DOCUMENT_NODE) {
        Document xmlDocNode = (Document)xmlNode;
        
        //if (xmlDocNode.getDoctype() == null) {
        //System.err.println("Doctype is null.");
        //}
        //else {
        if (xmlDocNode.getDoctype() != null) {
        DocumentType dt = xmlDocNode.getDoctype();
        
        String name = dt.getName();
        String pid  = dt.getPublicId();
        String sid  = dt.getSystemId();
        
        // Use previously assigned name, not dt.getName() again
        String doctype_str = "<!DOCTYPE " + name + " PUBLIC \"" + pid + "\" \"" + sid + "\">\n";
        
        xmlRepresentation.append(doctype_str);
        }
        getString(xmlDocNode.getDocumentElement(), xmlRepresentation, depth, pretty);
        return;
    }
    // Handle Element nodes
    if (nodeType == Node.ELEMENT_NODE) {
        if (pretty) {
        xmlRepresentation.append("\n");
        for (int i = 0; i < depth; i++) {
            xmlRepresentation.append("  ");
        }
        }

        // Write opening tag
        xmlRepresentation.append("<");
        xmlRepresentation.append(nodeName);
        
        // Write the node attributes
        NamedNodeMap nodeAttributes = xmlNode.getAttributes();
        for (int i = 0; i < nodeAttributes.getLength(); i++) {
        Node attribute = nodeAttributes.item(i);
        xmlRepresentation.append(" ");
        xmlRepresentation.append(attribute.getNodeName());
        xmlRepresentation.append("=\"");
        xmlRepresentation.append(attribute.getNodeValue());
        xmlRepresentation.append("\"");
        }

        // If the node has no children, close the opening tag and return
        if (xmlNode.hasChildNodes() == false) {
        // This produces somewhat ugly output, but it is necessary to compensate
        // for display bugs in Netscape. Firstly, the space is needed before the
        // closing bracket otherwise Netscape will ignore some tags (<br/>, for
        // example). Also, a newline character would be expected after the tag,
        // but this causes problems with the display of links (the link text
        // will contain a newline character, which is displayed badly).
        xmlRepresentation.append(" />");
        return;
        }
        
        // Close the opening tag
        xmlRepresentation.append(">");
        
        // Apply recursively to the children of this node
        // hack for nodes next to text nodes - dont make them pretty
        // this is needed for text inside a <pre> element - any new lines 
        // or spaces around the span elements show up in the text
        NodeList children = xmlNode.getChildNodes();
        boolean do_pretty = pretty;
        for (int i = 0; i < children.getLength(); i++) {
        if (children.item(i).getNodeType()==Node.TEXT_NODE) {
            do_pretty=false; // if there is a text node amongst the children, do teh following nodes in non-pretty mode - hope this doesn't stuff up something else
        }
        getString(children.item(i), xmlRepresentation, depth + 1, do_pretty);
        }
        
        // Write closing tag
        if (pretty) {
        if (xmlRepresentation.charAt(xmlRepresentation.length()-1) == '\n') {
            for (int i = 0; i < depth; i++)
            xmlRepresentation.append("  ");
        }
        }
        xmlRepresentation.append("</");
        xmlRepresentation.append(nodeName);
        xmlRepresentation.append(">");
        if (pretty) {
        xmlRepresentation.append("\n");
        }
    }
    
    // Handle Text nodes
    else if (nodeType == Node.TEXT_NODE) {
        String text = xmlNode.getNodeValue();

        // Perform output escaping, if required
        // Apache Commons replace method is far superior to String.replaceAll - very fast!
        if (outputEscaping) {

        text = StringUtils.replace(text, "&", "&amp;");
        text = StringUtils.replace(text, "<", "&lt;");
        text = StringUtils.replace(text, ">", "&gt;");
        text = StringUtils.replace(text, "'", "&apos;");
        text = StringUtils.replace(text, "\"", "&quot;");
        }

        // Remove any control-C characters
        text = StringUtils.replace(text, "" + (char)3, "");

        xmlRepresentation.append(text);
    }

    // Handle Processing Instruction nodes
    else if (nodeType == Node.PROCESSING_INSTRUCTION_NODE) {
        if (nodeName.equals("javax.xml.transform.disable-output-escaping")) {
        outputEscaping = false;
        }
        else if (nodeName.equals("javax.xml.transform.enable-output-escaping")) {
        outputEscaping = true;
        }
        else {
        logger.warn("Unhandled processing instruction " + nodeName);
        }
    }
    
    else if (nodeType == Node.COMMENT_NODE) {
        String text = xmlNode.getNodeValue();
        xmlRepresentation.append("<!-- ");
        xmlRepresentation.append(text);
        xmlRepresentation.append(" -->");
    }
        
        
    
    // A type of node that is not handled yet
    else {
        logger.warn("Unknown node type: " + nodeType+" "+getNodeTypeString(nodeType));
    }

    return;
    }

    protected static String getNodeTypeString(short node_type) {

    String type = "";
    switch(node_type) {
    case Node.ATTRIBUTE_NODE: 
        type="ATTRIBUTE_NODE";
        break;
    case Node.CDATA_SECTION_NODE:
        type="CDATA_SECTION_NODE";
        break;
    case Node.COMMENT_NODE:
        type="COMMENT_NODE";
        break;
    case Node.DOCUMENT_FRAGMENT_NODE:
        type="DOCUMENT_FRAGMENT_NODE";
        break;
    case Node.DOCUMENT_NODE:
        type="DOCUMENT_NODE";
        break;
    case Node.DOCUMENT_TYPE_NODE:
        type="DOCUMENT_TYPE_NODE";
        break;
    case Node.ELEMENT_NODE:
        type="ELEMENT_NODE";
        break;
    case Node.ENTITY_NODE:
        type="ENTITY_NODE";
        break;
    case Node.ENTITY_REFERENCE_NODE:
        type="ENTITY_REFERENCE_NODE";
        break;
    case Node.NOTATION_NODE:
        type="NOTATION_NODE";
        break;
    case Node.PROCESSING_INSTRUCTION_NODE:
        type="PROCESSING_INSTRUCTION_NODE";
        break;
    case Node.TEXT_NODE:
        type="TEXT_NODE";
        break;
    default:
        type="UNKNOWN";
    }

    return type;
    }
    
    // returns null if there no error occurred during parsing, or else returns the error message
    public String getParseErrorMessage() {
        ParseErrorHandler errorHandler = (ParseErrorHandler)this.parser.getErrorHandler();
        return errorHandler.getErrorMessage();
    }
    
    // Errorhandler for SAXParseExceptions that are errors, fatal errors or warnings. This class can be used to 
    // register a handler for any fatal errors, errors and warnings that may occur when parsing an xml file. The
    // errors are printed both to the greenstone.log and to the tomcat console (System.err), and the error message
    // is stored in the errorMessage variable so that it can be retrieved and be used to generate an xhtml error page.
    static public class ParseErrorHandler implements ErrorHandler {
        protected String errorMessage = null;
    
        //  Receive notification of a recoverable error.
        public void error(SAXParseException exception) {
            handleError("Error:\n", exception);
        }
        //   Receive notification of a non-recoverable error.
        public void fatalError(SAXParseException exception) {
            handleError("Fatal Error:\n", exception);
        }
        // Receive notification of a warning.
        public void warning(SAXParseException exception) {
            handleError("Warning:\n", exception);
        }
        
        public String toString(SAXParseException e) {
            String msg = e.getMessage();
            msg += "\nOn line(column): " + e.getLineNumber() + "(" + e.getColumnNumber() + ")";
            msg += (e.getPublicId() != null) ? ("\npublic ID: " + e.getPublicId()) : "\nNo public ID";
            msg += (e.getSystemId() != null) ? ("\nsystem ID: " + e.getSystemId()) : "\nNo system ID";
                    
            return msg;
        }
        
        // clears the errorPage variable after first call to this method
        public String getErrorMessage() {
            String errMsg = this.errorMessage;
            if(this.errorMessage != null) {
                this.errorMessage = null;
            }
            return errMsg;
        }
        
        // sets the errorMessage member variable to the data stored in the exception
        // and writes the errorMessage to the logger and tomcat's System.err
        protected void handleError(String errorType, SAXParseException exception) {
            this.errorMessage = errorType + toString(exception); 
            System.err.println("\n****Error parsing xml:\n" + this.errorMessage + "\n****\n");
            logger.error(this.errorMessage);
        }
    }
}