se.kb.xml.XPathWrapper.java Source code

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Here is the source code for se.kb.xml.XPathWrapper.java

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/*
 * Copyright 2008 National Library of Sweden 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 se.kb.xml;

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

import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.XPath;

import de.fhg.iais.commons.Cast;

/**
 * Helper class that eases the job of handling XPath queries and getting the different results. It wraps a {@link org.dom4j.Node} and then performs the XPath
 * queries on that.
 * 
 * @author Oskar Grenholm, National Library of Sweden
 */
public class XPathWrapper {

    private final Node node;
    private final Map<String, String> namespaces;

    /**
     * Wraps a <code>Node</code> for easier XPath handling.
     * 
     * @param node the <code>Node</code> to wrap
     */
    public XPathWrapper(Node node) {
        this(node, new HashMap<String, String>());
    }

    /**
     * Creates a <code>XPathWrapper</code> that should be aware of all the namespaces in the Map when handling
     * XPath queries.
     * 
     * @param node the <code>Node</code> to wrap
     * @param namespaces the namespaces
     */
    public XPathWrapper(Node node, Map<String, String> namespaces) {
        this.node = node;
        this.namespaces = namespaces;
    }

    /**
     * Adds a namespace that the wrapper should be aware of when performing XPath queries.
     * 
     * @param prefix the prefix of the namespace
     * @param uri the uri of the namespace
     */
    public void addNamespace(String prefix, String uri) {
        this.namespaces.put(prefix, uri);
    }

    /**
     * Selects a single node that matches the given XPath.
     * 
     * @param xpathExpression the xpath
     * @return a single <code>Node</code> or <code>null</code> if no match
     */
    public Node selectSingleNode(String xpathExpression) {
        XPath xpath = createXPath(xpathExpression);
        return xpath.selectSingleNode(this.node);
    }

    /**
     * Selects all <code>Nodes</code> that matches the given XPath.
     * 
     * @param xpathExpression the xpath
     * @return a list of nodes (can be empty if no matches)
     */
    public List<Node> selectNodes(final String xpathExpression) {
        final XPath xpath = createXPath(xpathExpression);

        final List<Node> result = Cast.nodeList(xpath.selectNodes(this.node));

        return result;
    }

    /**
     * Selects a single result that matches the given XPath and then casts it into a <code>Element</code>.
     * 
     * @param xpathExpression the xpath
     * @return a single <code>Element</code> or <code>null</code> if no match
     */
    public Element selectSingleElement(String xpathExpression) {
        return (Element) selectSingleNode(xpathExpression);
    }

    /**
     * Selects the value of the given XPath.
     * 
     * @param xpathExpression the xpath
     * @return the value or <code>null</code> if no match
     */
    public String valueOf(String xpathExpression) {
        XPath xpath = createXPath(xpathExpression);
        return xpath.valueOf(this.node);
    }

    private XPath createXPath(String xpathExpression) {
        XPath xpath = DocumentHelper.createXPath(xpathExpression);
        xpath.setNamespaceURIs(this.namespaces);
        return xpath;
    }
}