Main.java Source code

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Here is the source code for Main.java

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//package com.java2s;
/**
 * Copyright (C) 2010 http://flowas.net/
 *
 * 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.
 *
 * You can write to flowas@gmial.com for more customer requirement.
 */

import java.util.HashMap;

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.Node;

public class Main {
    private static final Map<String, XPathExpression> compiledExpressionCache = new HashMap<String, XPathExpression>();
    private static final XPath xpath = XPathFactory.newInstance().newXPath();

    /**
     * Checks in under a given root element whether it can find a child element
     * which matches the XPath expression supplied. The {@link Element} must
     * exist. Returns {@link Element} if exists.
     * 
     * 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 (required)
     * @param root the parent DOM element (required)
     * 
     * @return the Element if discovered (never null; an exception is thrown if
     *         cannot be found)
     */
    public static Element findRequiredElement(String xPathExpression, Element root) {
        //      Assert.hasText(xPathExpression, "XPath expression required");
        //      Assert.notNull(root, "Root element required");
        Element element = findFirstElement(xPathExpression, root);
        //      Assert.notNull(element, "Unable to obtain required element '" + xPathExpression + "' from element '" + root + "'");
        return element;
    }

    /**
     * Checks in under a given root element whether it can find a child element
     * which matches the XPath expression supplied. Returns {@link Element} if
     * exists.
     * 
     * 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 (required)
     * @param root the parent DOM element (required)
     * 
     * @return the Element if discovered (null if not found)
     */
    public static Element findFirstElement(String xPathExpression, Element root) {
        Node node = findNode(xPathExpression, root);
        if (node != null && node instanceof Element) {
            return (Element) node;
        }
        return null;
    }

    /**
     * Checks in under a given root element whether it can find a child node
     * which matches the XPath expression supplied. Returns {@link Node} if
     * exists.
     * 
     * 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 (required)
     * @param root the parent DOM element (required)
     * 
     * @return the Node if discovered (null if not found)
     */
    public static Node findNode(String xPathExpression, Element root) {
        if (xPathExpression == null || root == null || xPathExpression.length() == 0) {
            throw new IllegalArgumentException("Xpath expression and root element required");
        }
        Node node = null;
        try {
            XPathExpression expr = compiledExpressionCache.get(xPathExpression);
            if (expr == null) {
                expr = xpath.compile(xPathExpression);
                compiledExpressionCache.put(xPathExpression, expr);
            }
            node = (Node) expr.evaluate(root, XPathConstants.NODE);
        } catch (XPathExpressionException e) {
            throw new IllegalArgumentException("Unable evaluate xpath expression", e);
        }
        return node;
    }
}