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Easy Batch xml module
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/*
 * The MIT License
 *
 *  Copyright (c) 2015, Mahmoud Ben Hassine ([email protected])
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */

package org.easybatch.xml;

import org.easybatch.core.reader.RecordReader;
import org.easybatch.core.reader.RecordReaderClosingException;
import org.easybatch.core.reader.RecordReaderOpeningException;
import org.easybatch.core.reader.RecordReadingException;
import org.easybatch.core.record.Header;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.*;
import java.io.InputStream;
import java.util.Date;
import java.util.Iterator;

/**
 * A record reader that reads xml records from an xml stream.
 * 
 * This reader produces {@link XmlRecord} instances.
 *
 * @author Mahmoud Ben Hassine ([email protected])
 */
public class XmlRecordReader implements RecordReader {

    /**
     * The root element name.
     */
    private String rootElementName;

    /**
     * The xml input stream.
     */
    private InputStream xmlInputStream;

    /**
     * The xml reader.
     */
    private XMLEventReader xmlEventReader;

    /**
     * The current record number.
     */
    private long currentRecordNumber;

    public XmlRecordReader(final String rootElementName, final InputStream xmlInputStream) {
        this.rootElementName = rootElementName;
        this.xmlInputStream = xmlInputStream;
    }

    @Override
    public void open() throws RecordReaderOpeningException {
        currentRecordNumber = 0;
        try {
            xmlEventReader = XMLInputFactory.newInstance().createXMLEventReader(xmlInputStream);
        } catch (XMLStreamException e) {
            throw new RecordReaderOpeningException("Unable to open record reader", e);
        }
    }

    @Override
    public boolean hasNextRecord() {
        try {
            while (!nextTagIsRootElementStart()) {
                XMLEvent xmlEvent = xmlEventReader.nextEvent();
                if (xmlEvent instanceof EndDocument) {
                    return false;
                }
            }
            return true;
        } catch (Exception e) {
            return false;
        }
    }

    @Override
    public XmlRecord readNextRecord() throws RecordReadingException {
        StringBuilder stringBuilder = new StringBuilder("");
        try {
            while (!nextTagIsRootElementEnd()) {
                XMLEvent xmlEvent = xmlEventReader.nextEvent();
                if (xmlEvent.isStartElement()) {
                    escapeStartElementAttributes(stringBuilder, xmlEvent);
                } else if (xmlEvent.isEndElement()) {
                    writeEndElement(stringBuilder, xmlEvent);
                } else {
                    stringBuilder.append(xmlEvent.toString());
                }
            }
            writeEndElement(stringBuilder, xmlEventReader.nextEvent());
            Header header = new Header(++currentRecordNumber, getDataSourceName(), new Date());
            return new XmlRecord(header, stringBuilder.toString());
        } catch (XMLStreamException e) {
            throw new RecordReadingException("Unable to read next record", e);
        }
    }

    @Override
    public Long getTotalRecords() {
        return null;
    }

    @Override
    public String getDataSourceName() {
        return "XML stream";
    }

    @Override
    public void close() throws RecordReaderClosingException {
        try {
            if (xmlEventReader != null) {
                xmlEventReader.close();
            }
        } catch (XMLStreamException e) {
            throw new RecordReaderClosingException("Unable to close record reader", e);
        }
    }

    /**
     * Utility method to check if the next tag matches a start tag of the root element.
     *
     * @return true if the next tag matches a start element of the root element, false else
     * @throws XMLStreamException thrown if no able to peek the next xml element
     */
    private boolean nextTagIsRootElementStart() throws XMLStreamException {
        return xmlEventReader.peek().isStartElement() &&
                xmlEventReader.peek().asStartElement().getName().getLocalPart().equalsIgnoreCase(rootElementName);
    }

    /**
     * Utility method to check if the next tag matches an end tag of the root element.
     *
     * @return true if the next tag matches an end tag of the root element, false else
     * @throws XMLStreamException thrown if no able to peek the next xml element
     */
    private boolean nextTagIsRootElementEnd() throws XMLStreamException {
        return xmlEventReader.peek().isEndElement() &&
                xmlEventReader.peek().asEndElement().getName().getLocalPart().equalsIgnoreCase(rootElementName);
    }

    /**
     * Write end element.
     *
     * @param stringBuilder the string builder to write element into.
     * @throws XMLStreamException thrown when an exception occurs during xml streaming
     */
    private void writeEndElement(StringBuilder stringBuilder, XMLEvent xmlEvent) throws XMLStreamException {
        if (xmlEvent.isEndElement()) {
            EndElement endElement = xmlEvent.asEndElement();
            stringBuilder.append("");
        }
    }

    /**
     * Escape values of start element attributes.
     *
     * @param stringBuilder the builder in which writes escaped attributes.
     * @param xmlEvent      the start element to escape
     */
    private void escapeStartElementAttributes(StringBuilder stringBuilder, XMLEvent xmlEvent) {
        StartElement startElement = xmlEvent.asStartElement();
        stringBuilder.append("<").append(startElement.getName().getLocalPart());
        Iterator iterator = startElement.getAttributes();
        while (iterator.hasNext()) {
            Attribute attribute = iterator.next();
            stringBuilder.append(" ")
                    .append(attribute.getName())
                    .append("='")
                    .append(escape(attribute.getValue()))
                    .append("'");
        }
        stringBuilder.append(">");
    }

    /**
     * Escape the xml content. Only &, " and ' need to be escaped.
     *
     * @param xmlToEscape the xml content to escape
     * @return the escaped xml
     */
    private String escape(String xmlToEscape) {
        return xmlToEscape.replaceAll("&", "&")
                .replaceAll("'", "'")
                .replaceAll("\"", """);
    }

}