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 */
017package org.apache.commons.jxpath;
018
019import java.util.ArrayList;
020import java.util.HashMap;
021import java.util.Iterator;
022import java.util.List;
023import 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 */
034public 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}