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Java > Open Source Codes > org > apache > excalibur > instrument > InstrumentProxy


1 /*
2
3  ============================================================================
4                    The Apache Software License, Version 1.1
5  ============================================================================
6  
7  Copyright (C) 1999-2003 The Apache Software Foundation. All rights reserved.
8  
9  Redistribution and use in source and binary forms, with or without modifica-
10  tion, are permitted provided that the following conditions are met:
11  
12  1. Redistributions of source code must retain the above copyright notice,
13     this list of conditions and the following disclaimer.
14  
15  2. Redistributions in binary form must reproduce the above copyright notice,
16     this list of conditions and the following disclaimer in the documentation
17     and/or other materials provided with the distribution.
18  
19  3. The end-user documentation included with the redistribution, if any, must
20     include the following acknowledgment: "This product includes software
21     developed by the Apache Software Foundation (http://www.apache.org/)."
22     Alternately, this acknowledgment may appear in the software itself, if
23     and wherever such third-party acknowledgments normally appear.
24  
25  4. The names "Jakarta", "Avalon", "Excalibur" and "Apache Software Foundation"
26     must not be used to endorse or promote products derived from this software
27     without prior written permission. For written permission, please contact
28     apache@apache.org.
29  
30  5. Products derived from this software may not be called "Apache", nor may
31     "Apache" appear in their name, without prior written permission of the
32     Apache Software Foundation.
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34  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
35  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
36  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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39  DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
40  OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
41  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
42  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
43  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44  
45  This software consists of voluntary contributions made by many individuals
46  on behalf of the Apache Software Foundation. For more information on the
47  Apache Software Foundation, please see <http://www.apache.org/>.
48  
49 */
50 package org.apache.excalibur.instrument;
51
52 /**
53  * Because some components using Instruments will be created in large numbers
54  * a way is needed to collect data from the instances of all instances of a
55  * component class without maintaining references to Instruments of each
56  * instance. An Instrument Manager can do this by making use of Instrument
57  * Proxies. Each Instrument is assigned a proxy when it is registered with
58  * the manager, then all communication is made through the proxy
59  * The Instrument interface must by implemented by any object wishing to act
60  * as an instrument used by the instrument manager.
61  *
62  * @author <a HREF="mailto:leif@tanukisoftware.com">Leif Mortenson</a>
63  * @version CVS $Revision: 1.2 $ $Date: 2003/02/20 17:07:55 $
64  * @since 4.1
65  */
66 public interface InstrumentProxy
67 {
68     /**
69      * Used by classes being profiles so that they can avoid unnecessary
70      * code when the data from a Instrument is not being used.
71      *
72      * @return True if listeners are registered with the Instrument.
73      */
74     boolean isActive();
75
76     /**
77      * Increments the Instrument by a specified count. This method should be
78      * optimized to be extremely light weight when there are no registered
79      * CounterInstrumentListeners.
80      * <p>
81      * This method may throw an IllegalStateException if the proxy is not meant
82      * to handle calls to increment.
83      *
84      * @param count A positive integer to increment the counter by.
85      */
86     void increment( int count );
87
88     /**
89      * Sets the current value of the Instrument. This method is optimized
90      * to be extremely light weight when there are no registered
91      * ValueInstrumentListeners.
92      * <p>
93      * This method may throw an IllegalStateException if the proxy is not meant
94      * to handle calls to setValue.
95      *
96      * @param value The new value for the Instrument.
97      */
98     void setValue( int value );
99 }
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