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Java > Open Source Codes > org > apache > excalibur > event > EnqueuePredicate


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
12  * implied.
13  *
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 package org.apache.excalibur.event;
18
19
20 /**
21  * Enqueue predicates allow users to specify a method that
22  * will 'screen' elements being enqueued onto a sink, either
23  * accepting or rejecting them. This mechanism can be used
24  * to implement many interesting load-conditioning policies,
25  * for example, simple thresholding, rate control, credit-based
26  * flow control, and so forth. Note that the enqueue predicate
27  * runs in the context of the <b>caller of enqueue()</b>, which
28  * means it must be simple and fast.
29  *
30  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
31  * @version $Revision: 1.4 $
32  */
33 public interface EnqueuePredicate
34 {
35     /**
36      * Tests the given element for acceptance onto the m_sink.
37      * @since Feb 10, 2003
38      *
39      * @param element The element to enqueue
40      * @param modifyingSink The sink that is used for this predicate
41      * @return
42      * <code>true</code> if the sink accepts the element;
43      * <code>false</code> otherwise.
44      */
45     boolean accept(Object JavaDoc element, Sink modifyingSink);
46
47     /**
48      * Tests the given element for acceptance onto the m_sink.
49      * @since Feb 10, 2003
50      *
51      * @param elements The array of elements to enqueue
52      * @param modifyingSink The sink that is used for this predicate
53      * @return
54      * <code>true</code> if the sink accepts all the elements;
55      * <code>false</code> otherwise.
56      */
57     boolean accept(Object JavaDoc elements[], Sink modifyingSink);
58 }
59
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