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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;

Acts as a holder for an XML Source in the form of a StAX reader,i.e. XMLStreamReader or XMLEventReader. StAXSource can be used in all cases that accept
a Source, e.g. Transformer, Validator which accept Source as input.
StAXSources are consumed during processing
and are not reusable.
Author:
Neeraj Bajaj, Jeff Suttor
See Also:

 *  JSR 173: Streaming API for XML
XMLStreamReader
XMLEventReader
Since:
1.6/**
 * <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 Neeraj Bajaj
 * @author Jeff Suttor
 *
 * @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 TransformerFactory.getFeature(String name) returns true when passed this value as an argument, the Transformer supports Source input of this type. /** 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";

    
XMLEventReader to be used for source input.
 /** <p><code>XMLEventReader</code> to be used for source input.</p> */
    private XMLEventReader xmlEventReader = null;

    
XMLStreamReader to be used for source input.
 /** <p><code>XMLStreamReader</code> to be used for source input.</p> */
    private XMLStreamReader xmlStreamReader = null;

    
System identifier of source input.
 /** <p>System identifier of source input.</p> */
    private String systemId = null;

    
Creates a new instance of a StAXSource by supplying an XMLEventReader.
XMLEventReader must be a
non-null reference.
XMLEventReader must be in XMLStreamConstants.START_DOCUMENT or XMLStreamConstants.START_ELEMENT state.
Params:
xmlEventReader – XMLEventReader used to create
  this StAXSource.
Throws:
XMLStreamException – If xmlEventReader access
  throws an Exception.
IllegalArgumentException – If xmlEventReader ==
  null.
IllegalStateException – If xmlEventReader
  is not in XMLStreamConstants.START_DOCUMENT or
  XMLStreamConstants.START_ELEMENT state./**
     * <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();
    }

    
Creates a new instance of a StAXSource by supplying an XMLStreamReader.
XMLStreamReader must be a
non-null reference.
XMLStreamReader must be in XMLStreamConstants.START_DOCUMENT or XMLStreamConstants.START_ELEMENT state.
Params:
xmlStreamReader – XMLStreamReader used to create
  this StAXSource.
Throws:
IllegalArgumentException – If xmlStreamReader ==
  null.
IllegalStateException – If xmlStreamReader
  is not in XMLStreamConstants.START_DOCUMENT or
  XMLStreamConstants.START_ELEMENT state./**
     * <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();
    }

    
Get the XMLEventReader used by this
StAXSource.
XMLEventReader will be null.
if this StAXSource was created with a
XMLStreamReader.
Returns:
XMLEventReader used by this
  StAXSource./**
     * <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;
    }

    
Get the XMLStreamReader used by this
StAXSource.
XMLStreamReader will be null
if this StAXSource was created with a
XMLEventReader.
Returns:
XMLStreamReader used by this
  StAXSource./**
     * <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;
    }

    
In the context of a StAXSource, it is not appropriate
to explicitly set the system identifier.
The XMLStreamReader or XMLEventReader
used to construct this StAXSource determines the
system identifier of the XML source.
An UnsupportedOperationException is always
thrown by this method.
Params:
systemId – Ignored.
Throws:
UnsupportedOperationException – Is always
  thrown by this method./**
     * <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.
     */
    @Override
    public void setSystemId(final String systemId) {

        throw new UnsupportedOperationException(
                "StAXSource#setSystemId(systemId) cannot set the "
                + "system identifier for a StAXSource");
    }

    
Get the system identifier used by this
StAXSource.
The XMLStreamReader or XMLEventReader
used to construct this StAXSource is queried to determine
the system identifier of the XML source.
The system identifier may be null or
an empty "" String.
Returns:
System identifier used by this 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>.
     */
    @Override
    public String getSystemId() {

        return systemId;
    }

    
Indicates whether the StAXSource object is empty. Since a StAXSource object can never be empty, this method always returns false. 
Returns:
unconditionally false/**
     * Indicates whether the {@code StAXSource} object is empty. Since a
     * {@code StAXSource} object can never be empty, this method always returns
     * false.
     *
     * @return unconditionally false
     */
    @Override
    public boolean isEmpty() {
        return false;
    }
}