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
018package org.apache.commons.jxpath;
019
020/**
021 * Extension function interface. Extension functions are grouped into {@link Functions Functions} objects, which are installed on JXPathContexts using the
022 * {@link JXPathContext#setFunctions JXPathContext.setFunctions()} call.
023 * <p>
024 * The Function interface can be implemented directly. However, most of the time JXPath's built-in implementations should suffice. See {@link ClassFunctions
025 * ClassFunctions} and {@link PackageFunctions PackageFunctions}.
026 */
027public interface Function {
028
029    /**
030     * Computes the value of the function. Each implementation of Function is responsible for conversion of supplied parameters to the required argument types.
031     *
032     * @param context    can be used to acquire the context in which the function is being evaluted.
033     * @param parameters function arguments
034     * @return Object result
035     */
036    Object invoke(ExpressionContext context, Object[] parameters);
037}