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    }