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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

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package javax.xml.transform.stax;

import javax.xml.stream.XMLEventReader;

import javax.xml.stream.XMLStreamConstants;

import javax.xml.stream.XMLStreamException;

import javax.xml.stream.XMLStreamReader;

import javax.xml.stream.events.XMLEvent;

import javax.xml.transform.Source;

/**

 * <p>Acts as a holder for an XML {@link Source} in the

 * form of a StAX reader,i.e.

 * {@link XMLStreamReader} or {@link XMLEventReader}.

 * <code>StAXSource</code> can be used in all cases that accept

 * a <code>Source</code>, e.g. {@link javax.xml.transform.Transformer},

 * {@link javax.xml.validation.Validator} which accept

 * <code>Source</code> as input.

 *

 * <p><code>StAXSource</code>s are consumed during processing

 * and are not reusable.</p>

 *

 * @author <a href="mailto:Neeraj.Bajaj@Sun.com">Neeraj Bajaj</a>

 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>

 *

 * @see <a href="http://jcp.org/en/jsr/detail?id=173">

 *  JSR 173: Streaming API for XML</a>

 * @see XMLStreamReader

 * @see XMLEventReader

 *

 * @since 1.6

 */

public class StAXSource implements Source {

    /** If {@link javax.xml.transform.TransformerFactory#getFeature(String name)}

     * returns true when passed this value as an argument,

     * the Transformer supports Source input of this type.

     */

    public static final String FEATURE =

        "http://javax.xml.transform.stax.StAXSource/feature";

    /** <p><code>XMLEventReader</code> to be used for source input.</p> */

    private XMLEventReader xmlEventReader = null;

    /** <p><code>XMLStreamReader</code> to be used for source input.</p> */

    private XMLStreamReader xmlStreamReader = null;

    /** <p>System identifier of source input.</p> */

    private String systemId = null;

    /**

     * <p>Creates a new instance of a <code>StAXSource</code>

     * by supplying an {@link XMLEventReader}.</p>

     *

     * <p><code>XMLEventReader</code> must be a

     * non-<code>null</code> reference.</p>

     *

     * <p><code>XMLEventReader</code> must be in

     * {@link XMLStreamConstants#START_DOCUMENT} or

     * {@link XMLStreamConstants#START_ELEMENT} state.</p>

     *

     * @param xmlEventReader <code>XMLEventReader</code> used to create

     *   this <code>StAXSource</code>.

     *

     * @throws XMLStreamException If <code>xmlEventReader</code> access

     *   throws an <code>Exception</code>.

     * @throws IllegalArgumentException If <code>xmlEventReader</code> ==

     *   <code>null</code>.

     * @throws IllegalStateException If <code>xmlEventReader</code>

     *   is not in <code>XMLStreamConstants.START_DOCUMENT</code> or

     *   <code>XMLStreamConstants.START_ELEMENT</code> state.

     */

    public StAXSource(final XMLEventReader xmlEventReader)

        throws XMLStreamException {

        if (xmlEventReader == null) {

            throw new IllegalArgumentException(

                    "StAXSource(XMLEventReader) with XMLEventReader == null");

        }

        // TODO: This is ugly ...

        // there is no way to know the current position(event) of

        // XMLEventReader.  peek() is the only way to know the next event.

        // The next event on the input stream should be

        // XMLStreamConstants.START_DOCUMENT or

        // XMLStreamConstants.START_ELEMENT.

        XMLEvent event = xmlEventReader.peek();

        int eventType = event.getEventType();

        if (eventType != XMLStreamConstants.START_DOCUMENT

                && eventType != XMLStreamConstants.START_ELEMENT) {

            throw new IllegalStateException(

                "StAXSource(XMLEventReader) with XMLEventReader "

                + "not in XMLStreamConstants.START_DOCUMENT or "

                + "XMLStreamConstants.START_ELEMENT state");

        }

        this.xmlEventReader = xmlEventReader;

        systemId = event.getLocation().getSystemId();

    }

    /**

     * <p>Creates a new instance of a <code>StAXSource</code>

     * by supplying an {@link XMLStreamReader}.</p>

     *

     * <p><code>XMLStreamReader</code> must be a

     * non-<code>null</code> reference.</p>

     *

     * <p><code>XMLStreamReader</code> must be in

     * {@link XMLStreamConstants#START_DOCUMENT} or

     * {@link XMLStreamConstants#START_ELEMENT} state.</p>

     *

     * @param xmlStreamReader <code>XMLStreamReader</code> used to create

     *   this <code>StAXSource</code>.

     *

     * @throws IllegalArgumentException If <code>xmlStreamReader</code> ==

     *   <code>null</code>.

     * @throws IllegalStateException If <code>xmlStreamReader</code>

     *   is not in <code>XMLStreamConstants.START_DOCUMENT</code> or

     *   <code>XMLStreamConstants.START_ELEMENT</code> state.

     */

    public StAXSource(final XMLStreamReader xmlStreamReader) {

        if (xmlStreamReader == null) {

            throw new IllegalArgumentException(

                    "StAXSource(XMLStreamReader) with XMLStreamReader == null");

        }

        int eventType = xmlStreamReader.getEventType();

        if (eventType != XMLStreamConstants.START_DOCUMENT

                && eventType != XMLStreamConstants.START_ELEMENT) {

            throw new IllegalStateException(

                    "StAXSource(XMLStreamReader) with XMLStreamReader"

                    + "not in XMLStreamConstants.START_DOCUMENT or "

                    + "XMLStreamConstants.START_ELEMENT state");

        }

        this.xmlStreamReader = xmlStreamReader;

        systemId = xmlStreamReader.getLocation().getSystemId();

    }

    /**

     * <p>Get the <code>XMLEventReader</code> used by this

     * <code>StAXSource</code>.</p>

     *

     * <p><code>XMLEventReader</code> will be <code>null</code>.

     * if this <code>StAXSource</code> was created with a

     * <code>XMLStreamReader</code>.</p>

     *

     * @return <code>XMLEventReader</code> used by this

     *   <code>StAXSource</code>.

     */

    public XMLEventReader getXMLEventReader() {

        return xmlEventReader;

    }

    /**

     * <p>Get the <code>XMLStreamReader</code> used by this

     * <code>StAXSource</code>.</p>

     *

     * <p><code>XMLStreamReader</code> will be <code>null</code>

     * if this <code>StAXSource</code> was created with a

     * <code>XMLEventReader</code>.</p>

     *

     * @return <code>XMLStreamReader</code> used by this

     *   <code>StAXSource</code>.

     */

    public XMLStreamReader getXMLStreamReader() {

        return xmlStreamReader;

    }

    /**

     * <p>In the context of a <code>StAXSource</code>, it is not appropriate

     * to explicitly set the system identifier.

     * The <code>XMLStreamReader</code> or <code>XMLEventReader</code>

     * used to construct this <code>StAXSource</code> determines the

     * system identifier of the XML source.</p>

     *

     * <p>An {@link UnsupportedOperationException} is <strong>always</strong>

     * thrown by this method.</p>

     *

     * @param systemId Ignored.

     *

     * @throws UnsupportedOperationException Is <strong>always</strong>

     *   thrown by this method.

     */

    public void setSystemId(final String systemId) {

        throw new UnsupportedOperationException(

                "StAXSource#setSystemId(systemId) cannot set the "

                + "system identifier for a StAXSource");

    }

    /**

     * <p>Get the system identifier used by this

     * <code>StAXSource</code>.</p>

     *

     * <p>The <code>XMLStreamReader</code> or <code>XMLEventReader</code>

     * used to construct this <code>StAXSource</code> is queried to determine

     * the system identifier of the XML source.</p>

     *

     * <p>The system identifier may be <code>null</code> or

     * an empty <code>""</code> <code>String</code>.</p>

     *

     * @return System identifier used by this <code>StAXSource</code>.

     */

    public String getSystemId() {

        return systemId;

    }

}