ApplyXPathDOM.java Source code

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Here is the source code for ApplyXPathDOM.java

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/*
 * 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.
 */
/*
 * $Id$
 */
// This file uses 4 space indents, no tabs.

import java.io.FileInputStream;
import java.io.OutputStreamWriter;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.apache.xpath.domapi.XPathEvaluatorImpl;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.xpath.XPathEvaluator;
import org.w3c.dom.xpath.XPathNSResolver;
import org.w3c.dom.xpath.XPathResult;
import org.xml.sax.InputSource;

/**
 *  Very basic utility for applying the DOM L3 XPath API (currently in Last Call)
 *  to an xml file and printing information about the execution of the XPath object 
 *  and the nodes it finds.
 *  Takes 2 arguments:
 *     (1) an xml filename
 *     (2) an XPath expression to apply to the file
 *  Examples:
 *     java ApplyXPathDOM foo.xml /
 *     java ApplyXPathDOM foo.xml /doc/name[1]/@last
 *
 *<p>See also the <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document Object Model (DOM) Level 3 XPath Specification</a>.</p>
 * @see XPathEvaluator
 * 
 */
public class ApplyXPathDOM {
    protected String filename = null;
    protected String xpath = null;

    /** Process input args and execute the XPath.  */
    public void doMain(String[] args) throws Exception {
        filename = args[0];
        xpath = args[1];

        if ((filename != null) && (filename.length() > 0) && (xpath != null) && (xpath.length() > 0)) {
            // Tell that we're loading classes and parsing, so the time it 
            // takes to do this doesn't get confused with the time to do 
            // the actual query and serialization.
            System.out.println("Loading classes, parsing " + filename + ", and setting up serializer");

            // Set up a DOM tree to query.
            InputSource in = new InputSource(new FileInputStream(filename));
            DocumentBuilderFactory dfactory = DocumentBuilderFactory.newInstance();
            dfactory.setNamespaceAware(true);
            Document doc = dfactory.newDocumentBuilder().parse(in);

            // Set up an identity transformer to use as serializer.
            Transformer serializer = TransformerFactory.newInstance().newTransformer();
            serializer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

            // Use the DOM L3 XPath API to apply the xpath expression to the doc.
            System.out.println("Querying DOM using " + xpath);

            // Create an XPath evaluator and pass in the document.
            XPathEvaluator evaluator = new XPathEvaluatorImpl(doc);
            XPathNSResolver resolver = evaluator.createNSResolver(doc);

            // Evaluate the xpath expression
            XPathResult result = (XPathResult) evaluator.evaluate(xpath, doc, resolver,
                    XPathResult.UNORDERED_NODE_ITERATOR_TYPE, null);

            // Serialize the found nodes to System.out.
            System.out.println("<output>");

            Node n;
            while ((n = result.iterateNext()) != null) {
                if (isTextNode(n)) {
                    // DOM may have more than one node corresponding to a 
                    // single XPath text node.  Coalesce all contiguous text nodes
                    // at this level
                    StringBuffer sb = new StringBuffer(n.getNodeValue());
                    for (Node nn = n.getNextSibling(); isTextNode(nn); nn = nn.getNextSibling()) {
                        sb.append(nn.getNodeValue());
                    }
                    System.out.print(sb);
                } else {
                    serializer.transform(new DOMSource(n), new StreamResult(new OutputStreamWriter(System.out)));
                }
                System.out.println();
            }
            System.out.println("</output>");
        } else {
            System.out.println("Bad input args: " + filename + ", " + xpath);
        }
    }

    /** Decide if the node is text, and so must be handled specially */
    static boolean isTextNode(Node n) {
        if (n == null)
            return false;
        short nodeType = n.getNodeType();
        return nodeType == Node.CDATA_SECTION_NODE || nodeType == Node.TEXT_NODE;
    }

    /** Main method to run from the command line.    */
    public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            System.out.println("java ApplyXPathDOM filename.xml xpath\n"
                    + "Reads filename.xml and applies the xpath; prints the nodelist found.");
            return;
        }

        ApplyXPathDOM app = new ApplyXPathDOM();
        app.doMain(args);
    }

} // end of class ApplyXPathDOM