# FDFAnnotationLink.java

    /*
     * 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.
     */
    package org.apache.pdfbox.pdmodel.fdf;

    import java.io.IOException;

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

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;

    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSName;
    import org.apache.pdfbox.pdmodel.interactive.action.PDActionURI;

    import org.w3c.dom.Element;
    import org.w3c.dom.Node;
    import org.w3c.dom.NodeList;

    /**
     * This represents a Polygon FDF annotation.
     */
    public class FDFAnnotationLink extends FDFAnnotation
    {
        private static final Log LOG = LogFactory.getLog(FDFAnnotationLink.class);

        /**
         * COS Model value for SubType entry.
         */
        public static final String SUBTYPE = "Link";

        /**
         * Default constructor.
         */
        public FDFAnnotationLink()
        {
            annot.setName(COSName.SUBTYPE, SUBTYPE);
        }

        /**
         * Constructor.
         *
         * @param a An existing FDF Annotation.
         */
        public FDFAnnotationLink(COSDictionary a)
        {
            super(a);
        }

        /**
         * Constructor.
         *
         * @param element An XFDF element.
         *
         * @throws IOException If there is an error extracting information from the element.
         */
        public FDFAnnotationLink(Element element) throws IOException
        {
            super(element);
            annot.setName(COSName.SUBTYPE, SUBTYPE);
            XPath xpath = XPathFactory.newInstance().newXPath();

            try
            {
                NodeList uri = (NodeList) xpath.evaluate("OnActivation/Action/URI", element,
                        XPathConstants.NODESET);
                if (uri.getLength() > 0)
                {
                    Node namedItem = uri.item(0).getAttributes().getNamedItem("Name");
                    if (namedItem != null && namedItem.getNodeValue() != null)
                    {
                        PDActionURI actionURI = new PDActionURI();
                        actionURI.setURI(namedItem.getNodeValue());
                        annot.setItem(COSName.A, actionURI);
                    }
                }
                // GoTo is more tricky, because because page destination needs page tree
                // to convert number into PDPage object
            }
            catch (XPathExpressionException e)
            {
                LOG.debug("Error while evaluating XPath expression", e);
            }
        }
    }