StAXSource.java 文件源码

/**
 * <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();
}