Function


1   /*
2    * Copyright 1999-2004 The Apache Software Foundation
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.jxpath;
17  
18  /**
19   * Extension function interface. Extension functions are grouped into
20   * {@link Functions Functions} objects, which are installed on
21   * JXPathContexts using the 
22   * {@link JXPathContext#setFunctions JXPathContext.setFunctions()}
23   * call.
24   * <p>
25   * The Function interface can be implemented directly. However,
26   * most of the time JXPath's built-in implementations should suffice.
27   * See {@link ClassFunctions ClassFunctions} and 
28   * {@link PackageFunctions PackageFunctions}.
29   *
30   * @author Dmitri Plotnikov
31   * @version $Revision: 1.7 $ $Date: 2004/02/29 14:17:42 $
32   */
33  public interface Function {
34  
35      /**
36       * Computes the value of the function. Each implementation of Function
37       * is responsible for conversion of supplied parameters to the required
38       * argument types.
39       *
40       * @param context can be used to acquire the context in which the
41       *    function is being evaluted.
42       */
43      Object   invoke(ExpressionContext context, Object  [] parameters);
44  }
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