XPathFinder.java

/*
 *    Copyright (c) 2013, University of Toronto.
 * 
 *    Licensed 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 edu.toronto.cs.xcurator.common;

import java.util.HashSet;
import java.util.Set;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

public class XPathFinder {

    private XPathFactory factory = XPathFactory.newInstance();

    /**
     * Get XML nodes by the XPath from the given element node
     *
     * @param path
     * @param element
     * @param nsContext
     * @return
     * @throws XPathExpressionException
     */
    public NodeList getNodesByPath(String path, Element element, NsContext nsContext)
            throws XPathExpressionException {
        XPath xpath = factory.newXPath();
        xpath.setNamespaceContext(nsContext);
        NodeList nodeList = (NodeList) xpath.evaluate(path, element, XPathConstants.NODESET);
        return nodeList;
    }

    /**
     * Get XML nodes by the XPath from the document
     *
     * @param path
     * @param document
     * @param nsContext
     * @return
     * @throws XPathExpressionException
     */
    public NodeList getNodesByPath(String path, Document document, NsContext nsContext)
            throws XPathExpressionException {
        XPath xpath = factory.newXPath();
        xpath.setNamespaceContext(nsContext);
        NodeList nodeList = (NodeList) xpath.evaluate(path, document, XPathConstants.NODESET);
        return nodeList;
    }

    public String getStringByPath(String path, Element element, NsContext nsContext)
            throws XPathExpressionException {
        XPath xpath = factory.newXPath();
        return ((String) xpath.evaluate(path, element, XPathConstants.STRING));
    }

    public NodeList getNodesByPath(String path, Element localElement, Document doc,
            NsContext nsContext) throws XPathExpressionException {
        // Note: if using absolute path, then the root element must also be specified,
        // that is, it should be like "/clinical_studies/clinical_study/..."
        XPath xpath = factory.newXPath();
        xpath.setNamespaceContext(nsContext);
        Object element = getElementToBeSearched(path, localElement, doc);
        NodeList nodeList = (NodeList) xpath.evaluate(path, element, XPathConstants.NODESET);
        return nodeList;
    }

    public boolean getBooleanPath(String path, Element localElement, Document doc,
            NsContext nsContext) throws XPathExpressionException {
        // Note: if using absolute path, then the root element must also be specified,
        // that is, it should be like "/clinical_studies/clinical_study/..."
        XPath xpath = factory.newXPath();
        Object element = getElementToBeSearched(path, localElement, doc);
        boolean res = (Boolean) xpath.evaluate(path, element, XPathConstants.BOOLEAN);
        return res;
    }

    public String getStringByPath(String path, Element localElement, Document doc,
            NsContext nsContext) throws XPathExpressionException {
        // Note the difference between this function and function "getStringsByPath"
        // The path for this function should be like "/clinical_studies/clinical_study/brief_title",
        // which returns ONLY ONE string of the first matched element "brief_title"
        XPath xpath = factory.newXPath();
        Object element = getElementToBeSearched(path, localElement, doc);
        return (String) xpath.evaluate(path, element, XPathConstants.STRING);
    }

    public Set<String> getStringsByPath(String path, Element localElement, Document doc,
            NsContext nsContext) throws XPathExpressionException {
        // Note the difference between this function and function "getStringByPath"
        // The path for this function should be like "/clinical_studies/clinical_study/brief_title/text()",
        // with the extra "/text()" at the end, and it returns ALL strings of ALL matching element "brief_title"
        Set<String> ret = new HashSet<String>();

        NodeList nl = getNodesByPath(path, localElement, doc, nsContext);
        for (int i = 0; i < nl.getLength(); i++) {
            if (nl.item(i) instanceof Text) {
                ret.add(((Text) nl.item(i)).getTextContent().trim());
            }
        }

        return ret;
    }

    private Object getElementToBeSearched(String path, Element localElement, Document doc) {
        return path.startsWith("/") || localElement == null ? doc : localElement;
    }
}