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Java > Open Source Codes > org > apache > beehive > netui > pageflow > interceptor > InterceptorChain


1 /*
2  * Copyright 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  * $Header:$
17  */
18 package org.apache.beehive.netui.pageflow.interceptor;
19
20 import java.util.List JavaDoc;
21 import java.util.LinkedList JavaDoc;
22
23 /**
24  * Base class for all chains of {@link Interceptor}s.
25  */
26 public abstract class InterceptorChain
27 {
28     private LinkedList JavaDoc/*< Interceptor >*/ _chain = new LinkedList JavaDoc/*< Interceptor >*/();
29     private InterceptorContext _context;
30     
31     protected InterceptorChain( InterceptorContext context, List JavaDoc/*< Interceptor >*/ interceptors )
32     {
33         _context = context;
34         _chain.addAll( interceptors );
35     }
36     
37     public Object JavaDoc continueChain()
38         throws InterceptorException
39     {
40         if ( ! _chain.isEmpty() )
41         {
42             return invoke( ( Interceptor ) _chain.removeFirst() );
43         }
44         else
45         {
46             return null;
47         }
48     }
49     
50     protected abstract Object JavaDoc invoke( Interceptor interceptor ) throws InterceptorException;
51     
52     public InterceptorContext getContext()
53     {
54         return _context;
55     }
56     
57     public boolean isEmpty()
58     {
59         return _chain.isEmpty();
60     }
61     
62     protected Interceptor removeFirst()
63     {
64         return ( Interceptor ) _chain.removeFirst();
65     }
66 }
67
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