xmlwriter.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// 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.
//
// For more information contact:
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//

package org.opennms.web.parsers;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Collection;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;
import org.opennms.core.resource.Vault;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

/**
 * This class is used to parse data from and save data to the users.xml file.
 * 
 * @author <A HREF="mailto:[e-mail]">Jason Johns </A>
 * @author <A HREF="http://www.opennms.org/">OpenNMS </A>
 * 
 * @version 1.1.1.1
 * 
 */
public abstract class XMLWriter {
    /**
     * The header information parsed from the file
     */
    protected static XMLHeader m_headerInfo;

    /**
     */
    protected Document m_document;

    /**
     */
    protected DocumentBuilder m_docBuilder;

    /**
     */
    protected String m_fileName;

    /**
     */
    protected String m_baseName;

    /**
     */
    protected String m_xmlPath;

    /**
     */
    protected String m_dtdPath;

    /**
     */
    protected String m_dtd;

    /**
     */
    protected static final String XML_EXTENSION = ".xml";

    /**
     */
    protected static final String DTD_EXTENSION = ".dtd";

    /**
     * Default constructor, intializes the member variables
     */
    public XMLWriter(String fileName) throws XMLWriteException {
        super();

        m_fileName = fileName;
        m_xmlPath = Vault.getProperty("opennms.home") + File.separator + "etc" + File.separator;

        m_dtdPath = Vault.getProperty("opennms.home") + File.separator + "etc" + File.separator;

        if (m_fileName.endsWith(XML_EXTENSION)) {
            m_baseName = m_fileName.substring(0, m_fileName.length() - XML_EXTENSION.length());
        } else {
            throw new XMLWriteException(m_fileName + " has an invalid extension for an xml file.");
        }

        try {
            DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
            m_docBuilder = docFactory.newDocumentBuilder();

            m_document = m_docBuilder.newDocument();
        } catch (Exception e) {
            throw new XMLWriteException(e.getMessage());
        }
    }

    /**
     */
    protected void loadDTD(String dtdFileName) throws FileNotFoundException, IOException {
        StringBuffer dtdBuffer = new StringBuffer();

        // open up the original file
        BufferedReader originalBuffer = new BufferedReader(new FileReader(dtdFileName));
        String input;
        while ((input = originalBuffer.readLine()) != null) {
            dtdBuffer.append(input).append("\n");
        }

        m_dtd = dtdBuffer.toString();
    }

    /**
     */
    public String getDTD(String dtdFileName) throws FileNotFoundException, IOException {
        String dtd = null;

        if (m_dtd != null) {
            dtd = m_dtd;
        } else {
            loadDTD(dtdFileName);

            if (m_dtd != null)
                dtd = m_dtd;
        }

        return dtd;
    }

    /**
     */
    public String getVersion() {
        String version = "?";
        String revTag = "$Revision:";

        try {
            String dtd = getDTD(m_dtdPath + m_baseName + DTD_EXTENSION);

            // find the $Revision comment
            int revStart = dtd.indexOf(revTag);
            int revEnd = dtd.indexOf("$", revStart + revTag.length());
            version = dtd.substring(revStart + revTag.length(), revEnd);
        } catch (Exception e) {
            // do nothing, a default value will be returned
        }

        return version.trim();
    }

    /**
     * This method attempts to make a backup of the xml file. It is recommended
     * that this method is called prior to making the call to save(), so that
     * the original config file will be recoverable if the writting of the new
     * config file fails.
     */
    public void backup() throws XMLWriteException {
        try {
            FileBackup.makeBackup(m_xmlPath + m_fileName, m_baseName);
        } catch (IOException e) {
            throw new XMLWriteException(e.getMessage());
        }
    }

    /**
     */
    protected void serializeToFile() throws XMLWriteException {
        try {
            FileWriter writer = new FileWriter(m_xmlPath + m_fileName);

            OutputFormat format = new OutputFormat(m_document);
            format.setOmitXMLDeclaration(true);
            format.setIndenting(true);

            XMLSerializer serializer = new XMLSerializer(writer, format);
            serializer.asDOMSerializer();

            // write the DTD, it has the XML Declare line in it
            writer.write(getDTD(m_dtdPath + m_baseName + DTD_EXTENSION));
            writer.write("\n");

            // write the DOM tree
            serializer.serialize(m_document);

            writer.flush();
            writer.close();
        } catch (Exception e) {
            throw new XMLWriteException(e.getMessage());
        }
    }

    /**
     */
    public Element addEmptyElement(Element parent, String elementName) {
        Element newElement = m_document.createElement(elementName);
        parent.appendChild(newElement);

        return newElement;
    }

    /**
     */
    public Element addDataElement(Element parent, String elementName, String data) {
        Element newElement = addEmptyElement(parent, elementName);

        newElement.appendChild(m_document.createTextNode(data));

        return newElement;
    }

    /**
     */
    public Element addCDataElement(Element parent, String elementName, String data) throws XMLWriteException {
        Element newElement = addEmptyElement(parent, elementName);

        try {
            newElement.appendChild(m_document.createCDATASection(data));
        } catch (DOMException e) {
            throw new XMLWriteException(e.getMessage());
        }

        return newElement;
    }

    /**
     */
    public void save(Collection list) throws XMLWriteException {
        // the saveDocument method rebuilds the xml document node by node, so
        // we need an empty document
        m_document = m_docBuilder.newDocument();

        saveDocument(list);
    }

    /**
     */
    abstract protected void saveDocument(Collection list) throws XMLWriteException;
}