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1   package org.apache.turbine.services;
2   
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  
22  /***
23   * Classes that implement this interface can act as a broker for
24   * <code>Initable</code> classes.
25   *
26   * Functionality provided by the broker includes:
27   *
28   * <ul>
29   *
30   * <li>Maintaining a single instance of each <code>Initable</code> in
31   * the system.</li>
32   *
33   * <li>Early initialization of <code>Initables</code> during system
34   * startup.</li>
35   *
36   * <li>Late initialization of <code>Initables</code> before they are
37   * used.</li>
38   *
39   * <li>Providing instances of <code>Initables</code> to requesting
40   * parties.</li>
41   *
42   * <li>Maintainging dependencies between <code>Initables</code> during
43   * early initalization phases, including circular dependencies
44   * detection.</li>
45   *
46   * </ul>
47   *
48   * @author <a href="mailto:burton@apache.org">Kevin Burton</a>
49   * @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a>
50   * @version $Id: InitableBroker.java 534527 2007-05-02 16:10:59Z tv $
51   */
52  public interface InitableBroker
53  {
54      /***
55       * Performs early initialization of an Initable class.
56       *
57       * If your class depends on another Initable being initialized to
58       * perform early initialization, you should always ask your broker
59       * to initialize the other class with the objects that are passed
60       * to you, before you try to retrieve that Initable's instance with
61       * getInitable().
62       *
63       * @param className The name of the class to be initailized.
64       * @param data An object to be used for initialization activities.
65       * @exception InitializationException if initialization of this
66       * class was not successful.
67       */
68      void initClass(String className, Object data)
69              throws InitializationException;
70  
71      /***
72       * Shutdowns an Initable class.
73       *
74       * This method is used to release resources allocated by an
75       * Initable class, and return it to initial (uninitailized)
76       * state.
77       *
78       * @param className The name of the class to be uninitialized.
79       */
80      void shutdownClass(String className);
81  
82      /***
83       * Provides an instance of Initable class ready to work.
84       *
85       * If the requested class couldn't be instatiated or initialized,
86       * InstantiationException will be thrown.  You needn't handle this
87       * exception in your code, since it indicates fatal
88       * misconfigurtion of the system.
89       *
90       * @param className The name of the Initable requested.
91       * @return An instance of requested Initable.
92       * @exception InstantiationException if there was a problem
93       * during instantiation or initialization of the Initable.
94       */
95      Initable getInitable(String className) throws InstantiationException;
96  }