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    /**
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 12:46:46 -0500 (Fri, 02 May 2008) $
033     */
034    public 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    }