org.apache.tomcat.util.digester.NodeCreateRule Maven / Gradle / Ivy
/* $Id: NodeCreateRule.java 467222 2006-10-24 03:17:11Z markt $
*
* 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.
*/
package org.apache.tomcat.util.digester;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Attr;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
* A rule implementation that creates a DOM
* {@link org.w3c.dom.Node Node} containing the XML at the element that matched
* the rule. Two concrete types of nodes can be created by this rule:
*
* - the default is to create an {@link org.w3c.dom.Element Element} node.
* The created element will correspond to the element that matched the rule,
* containing all XML content underneath that element.
* - alternatively, this rule can create nodes of type
* {@link org.w3c.dom.DocumentFragment DocumentFragment}, which will contain
* only the XML content under the element the rule was trigged on.
*
* The created node will be normalized, meaning it will not contain text nodes
* that only contain white space characters.
*
*
* The created Node will be pushed on Digester's object stack
* when done. To use it in the context of another DOM
* {@link org.w3c.dom.Document Document}, it must be imported first, using the
* Document method
* {@link org.w3c.dom.Document#importNode(org.w3c.dom.Node, boolean) importNode()}.
*
*
* Important Note: This is implemented by replacing the SAX
* {@link org.xml.sax.ContentHandler ContentHandler} in the parser used by
* Digester, and resetting it when the matched element is closed. As a side
* effect, rules that would match XML nodes under the element that matches
* a NodeCreateRule will never be triggered by Digester, which
* usually is the behavior one would expect.
*
* Note that the current implementation does not set the namespace prefixes
* in the exported nodes. The (usually more important) namespace URIs are set,
* of course.
*
* @since Digester 1.4
*/
public class NodeCreateRule extends Rule {
// ---------------------------------------------------------- Inner Classes
/**
* The SAX content handler that does all the actual work of assembling the
* DOM node tree from the SAX events.
*/
private class NodeBuilder
extends DefaultHandler {
// ------------------------------------------------------- Constructors
/**
* Constructor.
*
* Stores the content handler currently used by Digester so it can
* be reset when done, and initializes the DOM objects needed to
* build the node.
*
* @param doc the document to use to create nodes
* @param root the root node
* @throws ParserConfigurationException if the DocumentBuilderFactory
* could not be instantiated
* @throws SAXException if the XMLReader could not be instantiated by
* Digester (should not happen)
*/
public NodeBuilder(Document doc, Node root)
throws ParserConfigurationException, SAXException {
this.doc = doc;
this.root = root;
this.top = root;
oldContentHandler = digester.getXMLReader().getContentHandler();
}
// ------------------------------------------------- Instance Variables
/**
* The content handler used by Digester before it was set to this
* content handler.
*/
protected ContentHandler oldContentHandler = null;
/**
* Depth of the current node, relative to the element where the content
* handler was put into action.
*/
protected int depth = 0;
/**
* A DOM Document used to create the various Node instances.
*/
protected Document doc = null;
/**
* The DOM node that will be pushed on Digester's stack.
*/
protected Node root = null;
/**
* The current top DOM mode.
*/
protected Node top = null;
// --------------------------------------------- ContentHandler Methods
/**
* Appends a {@link org.w3c.dom.Text Text} node to the current node.
*
* @param ch the characters from the XML document
* @param start the start position in the array
* @param length the number of characters to read from the array
* @throws SAXException if the DOM implementation throws an exception
*/
public void characters(char[] ch, int start, int length)
throws SAXException {
try {
String str = new String(ch, start, length);
if (str.trim().length() > 0) {
top.appendChild(doc.createTextNode(str));
}
} catch (DOMException e) {
throw new SAXException(e.getMessage());
}
}
/**
* Checks whether control needs to be returned to Digester.
*
* @param namespaceURI the namespace URI
* @param localName the local name
* @param qName the qualified (prefixed) name
* @throws SAXException if the DOM implementation throws an exception
*/
public void endElement(String namespaceURI, String localName,
String qName)
throws SAXException {
try {
if (depth == 0) {
getDigester().getXMLReader().setContentHandler(
oldContentHandler);
getDigester().push(root);
getDigester().endElement(namespaceURI, localName, qName);
}
top = top.getParentNode();
depth--;
} catch (DOMException e) {
throw new SAXException(e.getMessage());
}
}
/**
* Adds a new
* {@link org.w3c.dom.ProcessingInstruction ProcessingInstruction} to
* the current node.
*
* @param target the processing instruction target
* @param data the processing instruction data, or null if none was
* supplied
* @throws SAXException if the DOM implementation throws an exception
*/
public void processingInstruction(String target, String data)
throws SAXException {
try {
top.appendChild(doc.createProcessingInstruction(target, data));
} catch (DOMException e) {
throw new SAXException(e.getMessage());
}
}
/**
* Adds a new child {@link org.w3c.dom.Element Element} to the current
* node.
*
* @param namespaceURI the namespace URI
* @param localName the local name
* @param qName the qualified (prefixed) name
* @param atts the list of attributes
* @throws SAXException if the DOM implementation throws an exception
*/
public void startElement(String namespaceURI, String localName,
String qName, Attributes atts)
throws SAXException {
try {
Node previousTop = top;
if ((localName == null) || (localName.length() == 0)) {
top = doc.createElement(qName);
} else {
top = doc.createElementNS(namespaceURI, localName);
}
for (int i = 0; i < atts.getLength(); i++) {
Attr attr = null;
if ((atts.getLocalName(i) == null) ||
(atts.getLocalName(i).length() == 0)) {
attr = doc.createAttribute(atts.getQName(i));
attr.setNodeValue(atts.getValue(i));
((Element)top).setAttributeNode(attr);
} else {
attr = doc.createAttributeNS(atts.getURI(i),
atts.getLocalName(i));
attr.setNodeValue(atts.getValue(i));
((Element)top).setAttributeNodeNS(attr);
}
}
previousTop.appendChild(top);
depth++;
} catch (DOMException e) {
throw new SAXException(e.getMessage());
}
}
}
// ----------------------------------------------------------- Constructors
/**
* Default constructor. Creates an instance of this rule that will create a
* DOM {@link org.w3c.dom.Element Element}.
*/
public NodeCreateRule() throws ParserConfigurationException {
this(Node.ELEMENT_NODE);
}
/**
* Constructor. Creates an instance of this rule that will create a DOM
* {@link org.w3c.dom.Element Element}, but lets you specify the JAXP
* DocumentBuilder that should be used when constructing the
* node tree.
*
* @param documentBuilder the JAXP DocumentBuilder to use
*/
public NodeCreateRule(DocumentBuilder documentBuilder) {
this(Node.ELEMENT_NODE, documentBuilder);
}
/**
* Constructor. Creates an instance of this rule that will create either a
* DOM {@link org.w3c.dom.Element Element} or a DOM
* {@link org.w3c.dom.DocumentFragment DocumentFragment}, depending on the
* value of the nodeType parameter.
*
* @param nodeType the type of node to create, which can be either
* {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} or
* {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE}
* @throws IllegalArgumentException if the node type is not supported
*/
public NodeCreateRule(int nodeType) throws ParserConfigurationException {
this(nodeType,
DocumentBuilderFactory.newInstance().newDocumentBuilder());
}
/**
* Constructor. Creates an instance of this rule that will create either a
* DOM {@link org.w3c.dom.Element Element} or a DOM
* {@link org.w3c.dom.DocumentFragment DocumentFragment}, depending on the
* value of the nodeType parameter. This constructor lets you
* specify the JAXP DocumentBuilder that should be used when
* constructing the node tree.
*
* @param nodeType the type of node to create, which can be either
* {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} or
* {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE}
* @param documentBuilder the JAXP DocumentBuilder to use
* @throws IllegalArgumentException if the node type is not supported
*/
public NodeCreateRule(int nodeType, DocumentBuilder documentBuilder) {
if (!((nodeType == Node.DOCUMENT_FRAGMENT_NODE) ||
(nodeType == Node.ELEMENT_NODE))) {
throw new IllegalArgumentException(
"Can only create nodes of type DocumentFragment and Element");
}
this.nodeType = nodeType;
this.documentBuilder = documentBuilder;
}
// ----------------------------------------------------- Instance Variables
/**
* The JAXP DocumentBuilder to use.
*/
private DocumentBuilder documentBuilder = null;
/**
* The type of the node that should be created. Must be one of the
* constants defined in {@link org.w3c.dom.Node Node}, but currently only
* {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} and
* {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE}
* are allowed values.
*/
private int nodeType = Node.ELEMENT_NODE;
// ----------------------------------------------------------- Rule Methods
/**
* Implemented to replace the content handler currently in use by a
* NodeBuilder.
*
* @param namespaceURI the namespace URI of the matching element, or an
* empty string if the parser is not namespace aware or the element has
* no namespace
* @param name the local name if the parser is namespace aware, or just
* the element name otherwise
* @param attributes The attribute list of this element
* @throws Exception indicates a JAXP configuration problem
*/
public void begin(String namespaceURI, String name, Attributes attributes)
throws Exception {
XMLReader xmlReader = getDigester().getXMLReader();
Document doc = documentBuilder.newDocument();
NodeBuilder builder = null;
if (nodeType == Node.ELEMENT_NODE) {
Element element = null;
if (getDigester().getNamespaceAware()) {
element =
doc.createElementNS(namespaceURI, name);
for (int i = 0; i < attributes.getLength(); i++) {
element.setAttributeNS(attributes.getURI(i),
attributes.getLocalName(i),
attributes.getValue(i));
}
} else {
element = doc.createElement(name);
for (int i = 0; i < attributes.getLength(); i++) {
element.setAttribute(attributes.getQName(i),
attributes.getValue(i));
}
}
builder = new NodeBuilder(doc, element);
} else {
builder = new NodeBuilder(doc, doc.createDocumentFragment());
}
xmlReader.setContentHandler(builder);
}
/**
* Pop the Node off the top of the stack.
*/
public void end() throws Exception {
Object top = digester.pop();
}
}