Mega Code Archive
Produce a SAX stream from a DOM Document
<![CDATA[
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: DOM2SAX.java 627367 2008-02-13 12:03:30Z maxberger $ */
import java.util.List;
import java.util.Map;
import java.util.Stack;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
import org.xml.sax.ext.LexicalHandler;
import org.xml.sax.helpers.AttributesImpl;
/**
* Helper class that produces a SAX stream from a DOM Document.
* <p>
* Part of the code here copied and adapted from Apache Xalan-J,
* src/org/apache/xalan/xsltc/trax/DOM2SAX.java
*/
public class DOM2SAX {
private static final String EMPTYSTRING = "";
private static final String XMLNS_PREFIX = "xmlns";
private ContentHandler contentHandler;
private LexicalHandler lexicalHandler;
private Map prefixes = new java.util.HashMap();
/**
* Main constructor
* @param handler the ContentHandler to send SAX events to
*/
public DOM2SAX(ContentHandler handler) {
this.contentHandler = handler;
if (handler instanceof LexicalHandler) {
this.lexicalHandler = (LexicalHandler)handler;
}
}
/**
* Writes the given document using the given ContentHandler.
* @param doc DOM document
* @param fragment if false no startDocument() and endDocument() calls are issued.
* @throws SAXException In case of a problem while writing XML
*/
public void writeDocument(Document doc, boolean fragment) throws SAXException {
if (!fragment) {
contentHandler.startDocument();
}
for (Node n = doc.getFirstChild(); n != null;
n = n.getNextSibling()) {
writeNode(n);
}
if (!fragment) {
contentHandler.endDocument();
}
}
/**
* Begin the scope of namespace prefix. Forward the event to the SAX handler
* only if the prefix is unknown or it is mapped to a different URI.
*/
private boolean startPrefixMapping(String prefix, String uri)
throws SAXException {
boolean pushed = true;
Stack uriStack = (Stack)prefixes.get(prefix);
if (uriStack != null) {
if (uriStack.isEmpty()) {
contentHandler.startPrefixMapping(prefix, uri);
uriStack.push(uri);
} else {
final String lastUri = (String) uriStack.peek();
if (!lastUri.equals(uri)) {
contentHandler.startPrefixMapping(prefix, uri);
uriStack.push(uri);
} else {
pushed = false;
}
}
} else {
contentHandler.startPrefixMapping(prefix, uri);
uriStack = new Stack();
prefixes.put(prefix, uriStack);
uriStack.push(uri);
}
return pushed;
}
/*
* End the scope of a name prefix by popping it from the stack and passing
* the event to the SAX Handler.
*/
private void endPrefixMapping(String prefix) throws SAXException {
final Stack uriStack = (Stack)prefixes.get(prefix);
if (uriStack != null) {
contentHandler.endPrefixMapping(prefix);
uriStack.pop();
}
}
/**
* If the DOM was created using a DOM 1.0 API, the local name may be null.
* If so, get the local name from the qualified name before generating the
* SAX event.
*/
private static String getLocalName(Node node) {
final String localName = node.getLocalName();
if (localName == null) {
final String qname = node.getNodeName();
final int col = qname.lastIndexOf(':');
return (col > 0) ? qname.substring(col + 1) : qname;
}
return localName;
}
/**
* Writes a node using the given writer.
* @param node node to serialize
* @throws SAXException In case of a problem while writing XML
*/
private void writeNode(Node node)
throws SAXException {
if (node == null) {
return;
}
switch (node.getNodeType()) {
case Node.ATTRIBUTE_NODE: // handled by ELEMENT_NODE
case Node.DOCUMENT_FRAGMENT_NODE:
case Node.DOCUMENT_TYPE_NODE:
case Node.ENTITY_NODE:
case Node.ENTITY_REFERENCE_NODE:
case Node.NOTATION_NODE:
// These node types are ignored!!!
break;
case Node.CDATA_SECTION_NODE:
final String cdata = node.getNodeValue();
if (lexicalHandler != null) {
lexicalHandler.startCDATA();
contentHandler.characters(cdata.toCharArray(), 0, cdata.length());
lexicalHandler.endCDATA();
} else {
// in the case where there is no lex handler, we still
// want the text of the cdate to make its way through.
contentHandler.characters(cdata.toCharArray(), 0, cdata.length());
}
break;
case Node.COMMENT_NODE: // should be handled!!!
if (lexicalHandler != null) {
final String value = node.getNodeValue();
lexicalHandler.comment(value.toCharArray(), 0, value.length());
}
break;
case Node.DOCUMENT_NODE:
contentHandler.startDocument();
Node next = node.getFirstChild();
while (next != null) {
writeNode(next);
next = next.getNextSibling();
}
contentHandler.endDocument();
break;
case Node.ELEMENT_NODE:
String prefix;
List pushedPrefixes = new java.util.ArrayList();
final AttributesImpl attrs = new AttributesImpl();
final NamedNodeMap map = node.getAttributes();
final int length = map.getLength();
// Process all namespace declarations
for (int i = 0; i < length; i++) {
final Node attr = map.item(i);
final String qnameAttr = attr.getNodeName();
// Ignore everything but NS declarations here
if (qnameAttr.startsWith(XMLNS_PREFIX)) {
final String uriAttr = attr.getNodeValue();
final int colon = qnameAttr.lastIndexOf(':');
prefix = (colon > 0) ? qnameAttr.substring(colon + 1)
: EMPTYSTRING;
if (startPrefixMapping(prefix, uriAttr)) {
pushedPrefixes.add(prefix);
}
}
}
// Process all other attributes
for (int i = 0; i < length; i++) {
final Node attr = map.item(i);
final String qnameAttr = attr.getNodeName();
// Ignore NS declarations here
if (!qnameAttr.startsWith(XMLNS_PREFIX)) {
final String uriAttr = attr.getNamespaceURI();
// Uri may be implicitly declared
if (uriAttr != null) {
final int colon = qnameAttr.lastIndexOf(':');
prefix = (colon > 0) ? qnameAttr.substring(0, colon)
: EMPTYSTRING;
if (startPrefixMapping(prefix, uriAttr)) {
pushedPrefixes.add(prefix);
}
}
// Add attribute to list
attrs.addAttribute(attr.getNamespaceURI(),
getLocalName(attr), qnameAttr, "CDATA", attr
.getNodeValue());
}
}
// Now process the element itself
final String qname = node.getNodeName();
final String uri = node.getNamespaceURI();
final String localName = getLocalName(node);
// Uri may be implicitly declared
if (uri != null) {
final int colon = qname.lastIndexOf(':');
prefix = (colon > 0) ? qname.substring(0, colon) : EMPTYSTRING;
if (startPrefixMapping(prefix, uri)) {
pushedPrefixes.add(prefix);
}
}
// Generate SAX event to start element
contentHandler.startElement(uri, localName, qname, attrs);
// Traverse all child nodes of the element (if any)
next = node.getFirstChild();
while (next != null) {
writeNode(next);
next = next.getNextSibling();
}
// Generate SAX event to close element
contentHandler.endElement(uri, localName, qname);
// Generate endPrefixMapping() for all pushed prefixes
final int nPushedPrefixes = pushedPrefixes.size();
for (int i = 0; i < nPushedPrefixes; i++) {
endPrefixMapping((String)pushedPrefixes.get(i));
}
break;
case Node.PROCESSING_INSTRUCTION_NODE:
contentHandler.processingInstruction(node.getNodeName(), node.getNodeValue());
break;
case Node.TEXT_NODE:
final String data = node.getNodeValue();
contentHandler.characters(data.toCharArray(), 0, data.length());
break;
default:
//nop
}
}
}
]]>