XMLStreamReaderFilter.java

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package org.glassfish.config.support;

import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.XMLEvent;
import javax.xml.stream.util.StreamReaderDelegate;

/**
 * {@link XMLStreamReader} wrapper that cuts off sub-trees.
 * @author Kohsuke Kawaguchi
 */
abstract class XMLStreamReaderFilter extends StreamReaderDelegate {
    XMLStreamReaderFilter(XMLStreamReader reader) {
        super(reader);
    }

    XMLStreamReaderFilter() {
    }

    public int next() throws XMLStreamException {
        while(true) {
            int r = super.next();
            if(r != START_ELEMENT || !filterOut())
                return r;
            skipTree();
        }
    }

    public int nextTag() throws XMLStreamException {
        while(true) {
            // Fix for issue 9127
            // The following call to super.nextTag() is replaced with thisNextTag() 
            int r = thisNextTag();
            if(r != START_ELEMENT || !filterOut())
                return r;
            skipTree();
        }
    }

    // Fix for issue 9127
    // This method is a modified version of the super.nextTag()
    // In addition to all other event types skipped in super.nextTag() in search for 
    // START_ELEMENT this method also includes DTD eventType in the skip-list 
    private int thisNextTag() throws XMLStreamException {
        int eventType = super.next();
        while((eventType == XMLStreamConstants.CHARACTERS && isWhiteSpace()) // skip whitespace
                || (eventType == XMLStreamConstants.CDATA && isWhiteSpace())
                // skip whitespace
                || eventType == XMLStreamConstants.SPACE
                || eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
                || eventType == XMLStreamConstants.COMMENT
                || eventType == XMLStreamConstants.DTD) {
            eventType = super.next();
        }

        if(eventType != XMLStreamConstants.START_ELEMENT && eventType != XMLStreamConstants.END_ELEMENT) {
            throw new XMLStreamException(
                    "found: " + getEventTypeString(eventType)
                    + ", expected " + getEventTypeString(XMLStreamConstants.START_ELEMENT)
                    + " or " + getEventTypeString(XMLStreamConstants.END_ELEMENT));
        }

        return eventType;

    }

    final static String getEventTypeString(int eventType) {
        switch (eventType) {
            case XMLEvent.START_ELEMENT:
                return "START_ELEMENT";
            case XMLEvent.END_ELEMENT:
                return "END_ELEMENT";
            case XMLEvent.PROCESSING_INSTRUCTION:
                return "PROCESSING_INSTRUCTION";
            case XMLEvent.CHARACTERS:
                return "CHARACTERS";
            case XMLEvent.COMMENT:
                return "COMMENT";
            case XMLEvent.START_DOCUMENT:
                return "START_DOCUMENT";
            case XMLEvent.END_DOCUMENT:
                return "END_DOCUMENT";
            case XMLEvent.ENTITY_REFERENCE:
                return "ENTITY_REFERENCE";
            case XMLEvent.ATTRIBUTE:
                return "ATTRIBUTE";
            case XMLEvent.DTD:
                return "DTD";
            case XMLEvent.CDATA:
                return "CDATA";
            case XMLEvent.SPACE:
                return "SPACE";
        }
        return "UNKNOWN_EVENT_TYPE, " + String.valueOf(eventType);
    }

    /**
     * Skips a whole subtree, and return with the cursor pointing to the end element
     * of the skipped subtree.
     */
    private void skipTree() throws XMLStreamException {
        int depth = 1;

        while(depth > 0) {
            // nextTag may cause problems.  We are just throwing it all away so
            // next() is fine...
            int r = super.next();

            if(r == START_ELEMENT) {
                depth++;
            }
            else if(r == END_ELEMENT) {
                depth--;
            }
            // else ignore everything else...
        }
    }

    /**
     * Called when the parser is at the start element state, to decide if we are to skip the current element
     * or not.
     */
    abstract boolean filterOut() throws XMLStreamException;
}