    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    }