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
019/**
020 * Extension function interface. Extension functions are grouped into
021 * {@link Functions Functions} objects, which are installed on
022 * JXPathContexts using the
023 * {@link JXPathContext#setFunctions JXPathContext.setFunctions()}
024 * call.
025 * <p>
026 * The Function interface can be implemented directly. However,
027 * most of the time JXPath's built-in implementations should suffice.
028 * See {@link ClassFunctions ClassFunctions} and
029 * {@link PackageFunctions PackageFunctions}.
030 *
031 * @author Dmitri Plotnikov
032 * @version $Revision: 652845 $ $Date: 2008-05-02 19:46:46 +0200 (Fr, 02 Mai 2008) $
033 */
034public interface Function {
035
036    /**
037     * Computes the value of the function. Each implementation of Function
038     * is responsible for conversion of supplied parameters to the required
039     * argument types.
040     *
041     * @param context can be used to acquire the context in which the
042     *    function is being evaluted.
043     * @param parameters function arguments
044     * @return Object result
045     */
046    Object invoke(ExpressionContext context, Object[] parameters);
047}