    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *     http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.jxpath;
    018
    019    import java.util.ArrayList;
    020    import java.util.HashMap;
    021    import java.util.Iterator;
    022    import java.util.List;
    023    import java.util.Set;
    024
    025    /**
    026     * An object that aggregates {@link Functions} objects into a group Functions
    027     * object. Since {@link JXPathContext} can only register a single Functions
    028     * object, FunctionLibrary should always be used to group all Functions objects
    029     * that need to be registered.
    030     *
    031     * @author Dmitri Plotnikov
    032     * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
    033     */
    034    public class FunctionLibrary implements Functions {
    035        private List allFunctions = new ArrayList();
    036        private HashMap byNamespace = null;
    037
    038        /**
    039         * Add functions to the library
    040         * @param functions to add
    041         */
    042        public void addFunctions(Functions functions) {
    043            allFunctions.add(functions);
    044            byNamespace = null;
    045        }
    046
    047        /**
    048         * Remove functions from the library.
    049         * @param functions to remove
    050         */
    051        public void removeFunctions(Functions functions) {
    052            allFunctions.remove(functions);
    053            byNamespace = null;
    054        }
    055
    056        /**
    057         * Returns a set containing all namespaces used by the aggregated
    058         * Functions.
    059         * @return Set<String>
    060         */
    061        public Set getUsedNamespaces() {
    062            if (byNamespace == null) {
    063                prepareCache();
    064            }
    065            return byNamespace.keySet();
    066        }
    067
    068        /**
    069         * Returns a Function, if any, for the specified namespace,
    070         * name and parameter types.
    071         * @param namespace function namespace
    072         * @param name function name
    073         * @param parameters parameters
    074         * @return Function found
    075         */
    076        public Function getFunction(String namespace, String name,
    077                Object[] parameters) {
    078            if (byNamespace == null) {
    079                prepareCache();
    080            }
    081            Object candidates = byNamespace.get(namespace);
    082            if (candidates instanceof Functions) {
    083                return ((Functions) candidates).getFunction(
    084                    namespace,
    085                    name,
    086                    parameters);
    087            }
    088            if (candidates instanceof List) {
    089                List list = (List) candidates;
    090                int count = list.size();
    091                for (int i = 0; i < count; i++) {
    092                    Function function =
    093                        ((Functions) list.get(i)).getFunction(
    094                            namespace,
    095                            name,
    096                            parameters);
    097                    if (function != null) {
    098                        return function;
    099                    }
    100                }
    101            }
    102            return null;
    103        }
    104
    105        /**
    106         * Prepare the cache.
    107         */
    108        private void prepareCache() {
    109            byNamespace = new HashMap();
    110            int count = allFunctions.size();
    111            for (int i = 0; i < count; i++) {
    112                Functions funcs = (Functions) allFunctions.get(i);
    113                Set namespaces = funcs.getUsedNamespaces();
    114                for (Iterator it = namespaces.iterator(); it.hasNext();) {
    115                    String ns = (String) it.next();
    116                    Object candidates = byNamespace.get(ns);
    117                    if (candidates == null) {
    118                        byNamespace.put(ns, funcs);
    119                    }
    120                    else if (candidates instanceof Functions) {
    121                        List lst = new ArrayList();
    122                        lst.add(candidates);
    123                        lst.add(funcs);
    124                        byNamespace.put(ns, lst);
    125                    }
    126                    else {
    127                        ((List) candidates).add(funcs);
    128                    }
    129                }
    130            }
    131        }
    132    }