xmlcontainerhelperimpl.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Library License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: XMLContainerHelperImpl.java,v 1.7 2000/11/09 14:56:53 daniela Exp $

package org.ozoneDB.xml.util;

import java.io.IOException;

import org.w3c.dom.Document;
import org.w3c.dom.Node;

import org.xml.sax.SAXException;

import org.ozoneDB.OzoneObject;
import org.ozoneDB.xml.dom.DocumentProxy;
import org.ozoneDB.xml.xpath.XtXPathProcessor;
import org.ozoneDB.xml.xpath.XPathProcessor;
import org.ozoneDB.xml.xpath.XPathQuery;
import org.ozoneDB.xml.xpath.XObject;


/**
 * This class provides server side part of the XMLContainer. It mainly handles
 * storing and retrieving of parts of the underlying XML document.
 * {@link SAXEventChunk} is used to exchange XML data between server and client.
 * 
 * 
 * @version $Revision: 1.7 $ $Date: 2000/11/09 14:56:53 $
 * @author <a href="http://www.smb-tec.com">SMB</a>
 */
public final class XMLContainerHelperImpl extends OzoneObject implements XMLContainerHelper {
    
    private final static long serialVersionUID = 4L;
    
    private final static boolean debug = XMLContainer.debug;
    
    /**
     */
    private static String xpathProcessorName;
    
    /**
     * The underlying XML document.
     */
    private Document document;
    
    static {
        xpathProcessorName = XtXPathProcessor.class.getName();
    } 
    
    
    public XMLContainerHelperImpl() {
        if (debug) {
            System.out.println( "helper: ctor..." );
        } 
    }
    
    
    public final void onCreate() throws Exception {
        if (debug) {
            System.out.println( "helper: onCreate()..." );
        } 
        document = (Document)database().createObject( org.ozoneDB.xml.dom.DocumentImpl.class.getName() );
        ((DocumentProxy)document).setContainer( this );
    } 
    
    
    public final void setDocument( Document _pdoc ) {
        if (debug) {
            System.out.println( "helper: setDocument..." );
        } 
        
        if (document != null) {
            throw new IllegalStateException( "Container helper is already assigned to a document." );
        } 
        
        document = _pdoc;
        ((DocumentProxy)document).setContainer( this );
    } 
    
    
    public final Document getDocument() {
        if (debug) {
            System.out.println( "helper: getDocument..." );
        } 
        
        return document;
    } 
    
    
    public final SAXChunkConsumer beginInputSequence( Node _pNode ) throws Exception {
        if (debug) {
            System.out.println("helper: beginInputSequence...");
        } 
        
        if (_pNode == null) {
            _pNode = getDocument();
        } 
        
        SAXChunkConsumer consumer = new SAXChunkConsumer( getDocument(), _pNode );
        return consumer;
    } 
    
    
    public final SAXChunkConsumer putChunk( byte[] _chunkData, SAXChunkConsumer _consumer ) 
            throws SAXException, IOException {
        _consumer.processChunk( _chunkData );
        return _consumer;
    } 
    
    
    public final void endInputSequence() throws Exception {
        if (debug) {
            System.out.println( "helper: endInputSequence..." );
        } 
    } 
    
    
    public final SAXChunkProducer beginOutputSequence( Node _pnode, int _depth ) throws Exception {
        if (_pnode == null) {
            _pnode = getDocument();
        } 
        return new SAXChunkProducer( _pnode, _depth );
    } 
    
    
    public final SAXChunkProducer createNextChunk( SAXChunkProducer producer ) throws SAXException {
        producer.createNextChunk();
        return producer;
    } 
    
    
    public final void endOutputSequence() throws Exception {
        if (debug) {
            System.out.println( "helper: endOutputSequence..." );
        } 
    } 
    
    
    // methods for XPath support
    
    
    public final static void setXPathProcessorName( String _classname ) throws ClassNotFoundException {
        if (_classname == null) {
            throw new IllegalArgumentException( "_name == null." );
        } 
        
        // just check if this class is available
        Class cl = Thread.currentThread().getContextClassLoader().loadClass( _classname );
        
        xpathProcessorName = _classname;
    } 
    
    
    public final XObject executeQuery( XPathQuery _query, Node _pNode ) 
            throws SAXException, ClassNotFoundException, InstantiationException, IllegalAccessException {
        if (_pNode == null) {
            _pNode = getDocument();
        } 

        // build a new processor in order to be able to handle several
        // requests in parallel
        Class cl = Thread.currentThread().getContextClassLoader().loadClass( xpathProcessorName );
        XPathProcessor processor = (XPathProcessor)cl.newInstance();
        return processor.execute( _query, _pNode );
    } 
    
    
    /**
     * Determines the absolute XPath for the given node.
     * @param node The W3C DOM node whose XPath is to determine.
     * @return The string representing the absolute XPath for this node.
     */
    public final String xpathForNode( Node _pnode ) {
        if (_pnode == null) {
            throw new IllegalArgumentException( "_pnode == null." );
        } 
        
        StringBuffer xpath = new StringBuffer();
        xpath = iterateBack( _pnode, xpath );
        return xpath.toString();
    } 
    
    
    // internal stuff
    
    
    private final StringBuffer iterateBack( Node node, StringBuffer buffer ) {
        int nthChild = 1;
        String nodeName = node.getNodeName();
        Node prevNode = node;
        while ((prevNode = prevNode.getPreviousSibling()) != null) {
            if (prevNode.getNodeName().equals( nodeName ) && prevNode.getNodeType() == node.getNodeType()) {
                nthChild++;
            } 
        } 
        if (node.getNodeType() == Node.TEXT_NODE) {
            nodeName = "text()";
        } else if (node.getNodeType() == Node.COMMENT_NODE) {
            nodeName = "comment()";
        } else {
            if (node.getNodeType() == Node.DOCUMENT_NODE) {
                nodeName = "";
            } 
        } 
        buffer.insert( 0, "/" + nodeName + (nodeName.length() > 0 ? "[" + nthChild + "]" : "") );
        node = node.getParentNode();
        if (node != null && node.getNodeType() != Node.DOCUMENT_NODE) {
            buffer = iterateBack( node, buffer );
        } 
        return buffer;
    } 
    
}