to.networld.semantic.contexthandler.common.RDFEntity.java Source code

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Here is the source code for to.networld.semantic.contexthandler.common.RDFEntity.java

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/**
 * context-handler - to.networld.semantic.contexthandler.common
 *
 * Copyright (C) 2011 by Networld Project
 * Written by Alex Oberhauser <oberhauseralex@networld.to>
 * 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, version 3 of the License.
 *
 * 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 software.  If not, see <http://www.gnu.org/licenses/>
 */

package to.networld.semantic.contexthandler.common;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentFactory;
import org.dom4j.Element;
import org.dom4j.QName;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

/**
 * Super class for all RDF/XML entities. Encapsulates the most
 * fundamental functionality for serialization.
 * 
 * @author Alex Oberhauser
 */
public class RDFEntity {
    private Config config;
    private final SAXReader reader;
    protected final Document document;
    protected final DocumentFactory documentFactory;

    protected RDFEntity() throws DocumentException {
        try {
            this.config = Config.getInstance();
        } catch (IOException e) {
            e.printStackTrace();
            this.config = null;
        }
        this.reader = new SAXReader();
        this.documentFactory = this.reader.getDocumentFactory();
        this.document = this.documentFactory.createDocument();
    }

    public Element createElement(QName _qname) {
        return this.documentFactory.createElement(_qname);
    }

    @Override
    public String toString() {
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        try {
            OutputFormat format = OutputFormat.createPrettyPrint();
            if (this.config != null) {
                format.setIndentSize(this.config.getRDFIndentSize());
                format.setExpandEmptyElements(this.config.getRDFExpandEmptyElements());
            }
            XMLWriter writer = new XMLWriter(os, format);
            writer.write(this.document);
            return os.toString();
        } catch (IOException e) {
            return null;
        }
    }

    /**
     * RDF/XML compact serialization. Hard to read for humans, but lower message size.
     * 
     * @return The representation of the context tag entry as RDF/XML.
     */
    public String toCompactRDF() {
        return this.document.asXML();
    }

}