impl/src/main/java/org/apache/taglibs/standard/tag/common/xml/JSTLPrefixResolver.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.taglibs.standard.tag.common.xml;

import java.util.HashMap;

import org.apache.xml.utils.PrefixResolver;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;

/**
 * <meta name="usage" content="general"/>
 * This class implements a JSTL PrefixResolver that
 * can be used to perform prefix-to-namespace lookup
 * for the XPath object.
 */
public class JSTLPrefixResolver implements PrefixResolver {

    /**
     * The context to resolve the prefix from, if the context
     * is not given.
     */

    HashMap namespaces;

    /**
     * The URI for the XML namespace.
     * (Duplicate of that found in org.apache.xpath.XPathContext).
     */

    public static final String S_XMLNAMESPACEURI =
            "http://www.w3.org/XML/1998/namespace";

    /**
     * No-arg constructor which would create empty HashMap of namespaces
     */
    public JSTLPrefixResolver() {
        namespaces = new HashMap();
    }

    public JSTLPrefixResolver(HashMap nses) {
        namespaces = nses;
    }

    /**
     * Given a namespace, get the corresponding prefix.  This assumes that
     * the PrevixResolver hold's it's own namespace context, or is a namespace
     * context itself.
     *
     * @param prefix Prefix to resolve.
     * @return Namespace that prefix resolves to, or null if prefix
     *         is not bound.
     */
    public String getNamespaceForPrefix(String prefix) {
        return (String) namespaces.get(prefix);
    }

    /**
     * Given a prefix and a Context Node, get the corresponding namespace.
     * Warning: This will not work correctly if namespaceContext
     * is an attribute node.
     *
     * @param prefix           Prefix to resolve.
     * @param namespaceContext Node from which to start searching for a
     *                         xmlns attribute that binds a prefix to a namespace.
     * @return Namespace that prefix resolves to, or null if prefix
     *         is not bound.
     */
    public String getNamespaceForPrefix(String prefix,
                                        org.w3c.dom.Node namespaceContext) {

        Node parent = namespaceContext;
        String namespace = null;

        if (prefix.equals("xml")) {
            namespace = S_XMLNAMESPACEURI;
        } else {
            int type;

            while ((null != parent) && (null == namespace)
                    && (((type = parent.getNodeType()) == Node.ELEMENT_NODE)
                    || (type == Node.ENTITY_REFERENCE_NODE))) {
                if (type == Node.ELEMENT_NODE) {
                    NamedNodeMap nnm = parent.getAttributes();

                    for (int i = 0; i < nnm.getLength(); i++) {
                        Node attr = nnm.item(i);
                        String aname = attr.getNodeName();
                        boolean isPrefix = aname.startsWith("xmlns:");

                        if (isPrefix || aname.equals("xmlns")) {
                            int index = aname.indexOf(':');
                            String p = isPrefix ? aname.substring(index + 1) : "";

                            if (p.equals(prefix)) {
                                namespace = attr.getNodeValue();

                                break;
                            }
                        }
                    }
                }

                parent = parent.getParentNode();
            }
        }

        return namespace;
    }

    /**
     * Return the base identifier.
     *
     * @return null
     */
    public String getBaseIdentifier() {
        return null;
    }

    /**
     * @see PrefixResolver#handlesNullPrefixes()
     */
    public boolean handlesNullPrefixes() {
        return false;
    }

    public void addNamespace(String prefix, String uri) {
        namespaces.put(prefix, uri);
    }

}