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1   /*
2    * $Id: PlugIn.java 471754 2006-11-06 14:55:09Z husted $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  package org.apache.struts.action;
22  
23  import org.apache.struts.config.ModuleConfig;
24  
25  import javax.servlet.ServletException;
26  
27  /**
28   * <p>A <strong>PlugIn</strong> is a configuration wrapper for a
29   * module-specific resource or service that needs to be notified about
30   * application startup and application shutdown events (corresponding to when
31   * the container calls <code>init</code> and <code>destroy</code> on the
32   * corresponding {@link ActionServlet} instance). <code>PlugIn</code> objects
33   * can be configured in the <code>struts-config.xml</code> file, without the
34   * need to subclass {@link ActionServlet} simply to perform application
35   * lifecycle activities.</p>
36   *
37   * <p>Implementations of this interface must supply a zero-argument
38   * constructor for use by {@link ActionServlet}. Configuration can be
39   * accomplished by providing standard JavaBeans property setter methods, which
40   * will all have been called before the <code>init()</code> method is
41   * invoked.</p>
42   *
43   * <p>This interface can be applied to any class, including an Action
44   * subclass. </p>
45   *
46   * @version $Rev: 471754 $ $Date: 2005-05-14 01:09:32 -0400 (Sat, 14 May 2005)
47   *          $
48   * @since Struts 1.1
49   */
50  public interface PlugIn {
51      /**
52       * <p>Receive notification that our owning module is being shut down.</p>
53       */
54      void destroy();
55  
56      /**
57       * <p>Receive notification that the specified module is being started
58       * up.</p>
59       *
60       * @param servlet ActionServlet that is managing all the modules in this
61       *                web application
62       * @param config  ModuleConfig for the module with which this plug-in is
63       *                associated
64       * @throws ServletException if this <code>PlugIn</code> cannot be
65       *                          successfully initialized
66       */
67      void init(ActionServlet servlet, ModuleConfig config)
68          throws ServletException;
69  }