Commons JXPath example source code file (FunctionLibrary.java)

This example Commons JXPath source code file (FunctionLibrary.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons JXPath tags/keywords

arraylist, function, functionlibrary, functions, functions, hashmap, iterator, list, list, object, object, set, string, string, util

The Commons JXPath FunctionLibrary.java source code

/*
 * 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.commons.jxpath;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

/**
 * An object that aggregates {@link Functions} objects into a group Functions
 * object. Since {@link JXPathContext} can only register a single Functions
 * object, FunctionLibrary should always be used to group all Functions objects
 * that need to be registered.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
 */
public class FunctionLibrary implements Functions {
    private List allFunctions = new ArrayList();
    private HashMap byNamespace = null;

    /**
     * Add functions to the library
     * @param functions to add
     */
    public void addFunctions(Functions functions) {
        allFunctions.add(functions);
        byNamespace = null;
    }

    /**
     * Remove functions from the library.
     * @param functions to remove
     */
    public void removeFunctions(Functions functions) {
        allFunctions.remove(functions);
        byNamespace = null;
    }

    /**
     * Returns a set containing all namespaces used by the aggregated
     * Functions.
     * @return Set<String>
     */
    public Set getUsedNamespaces() {
        if (byNamespace == null) {
            prepareCache();
        }
        return byNamespace.keySet();
    }

    /**
     * Returns a Function, if any, for the specified namespace,
     * name and parameter types.
     * @param namespace function namespace
     * @param name function name
     * @param parameters parameters
     * @return Function found
     */
    public Function getFunction(String namespace, String name,
            Object[] parameters) {
        if (byNamespace == null) {
            prepareCache();
        }
        Object candidates = byNamespace.get(namespace);
        if (candidates instanceof Functions) {
            return ((Functions) candidates).getFunction(
                namespace,
                name,
                parameters);
        }
        if (candidates instanceof List) {
            List list = (List) candidates;
            int count = list.size();
            for (int i = 0; i < count; i++) {
                Function function =
                    ((Functions) list.get(i)).getFunction(
                        namespace,
                        name,
                        parameters);
                if (function != null) {
                    return function;
                }
            }
        }
        return null;
    }

    /**
     * Prepare the cache.
     */
    private void prepareCache() {
        byNamespace = new HashMap();
        int count = allFunctions.size();
        for (int i = 0; i < count; i++) {
            Functions funcs = (Functions) allFunctions.get(i);
            Set namespaces = funcs.getUsedNamespaces();
            for (Iterator it = namespaces.iterator(); it.hasNext();) {
                String ns = (String) it.next();
                Object candidates = byNamespace.get(ns);
                if (candidates == null) {
                    byNamespace.put(ns, funcs);
                }
                else if (candidates instanceof Functions) {
                    List lst = new ArrayList();
                    lst.add(candidates);
                    lst.add(funcs);
                    byNamespace.put(ns, lst);
                }
                else {
                    ((List) candidates).add(funcs);
                }
            }
        }
    }
}