Java XPath Expression findElements(final String xPathExpression, final Element root)

Description

Checks in under a given root element whether it can find a child elements which match the XPath expression supplied.

License

Open Source License

Parameter

Parameter	Description
xPathExpression	the xPathExpression
root	the parent DOM element

Return

a of type if discovered, otherwise an empty list (never null)

Declaration

public static List<Element> findElements(final String xPathExpression,
        final Element root) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Element;

import org.w3c.dom.NodeList;

public class Main {
    private static final Map<String, XPathExpression> COMPILED_EXPRESSION_CACHE = new HashMap<String, XPathExpression>();
    private static final XPath XPATH = XPathFactory.newInstance()
            .newXPath();//  ww w.  j av a  2  s  .  c o m

    /**
     * Checks in under a given root element whether it can find a child elements
     * which match the XPath expression supplied. Returns a {@link List} of
     * {@link Element} if they exist. Please note that the XPath parser used is
     * NOT namespace aware. So if you want to find a element <beans><sec:http>
     * you need to use the following XPath expression '/beans/http'.
     * 
     * @param xPathExpression the xPathExpression
     * @param root the parent DOM element
     * @return a {@link List} of type {@link Element} if discovered, otherwise
     *         an empty list (never null)
     */
    public static List<Element> findElements(final String xPathExpression,
            final Element root) {
        final List<Element> elements = new ArrayList<Element>();
        NodeList nodes = null;

        try {
            XPathExpression expr = COMPILED_EXPRESSION_CACHE
                    .get(xPathExpression);
            if (expr == null) {
                expr = XPATH.compile(xPathExpression);
                COMPILED_EXPRESSION_CACHE.put(xPathExpression, expr);
            }
            nodes = (NodeList) expr.evaluate(root, XPathConstants.NODESET);
        } catch (final XPathExpressionException e) {
            throw new IllegalArgumentException(
                    "Unable evaluate xpath expression", e);
        }

        for (int i = 0, n = nodes.getLength(); i < n; i++) {
            elements.add((Element) nodes.item(i));
        }
        return elements;
    }
}

Related

1. expr(String xpathStr)
2. extractNode(XPath xpath, String nodePath, String xmlString)
3. extractNodeList(XPath xpath, String nodePath, String xmlString)
4. extractNodes(File xmlFile, String xpathLocator)
5. extractValue(String xml, String xpathExpression)
6. hasAnimatedPng(ImageReader reader)
7. isLegalXPath(final String xPath)
8. isValidFilter(String xPathString)
9. isXPathAbsolute(String path)