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Java > Open Source Codes > com > db4o > tools > QueryStats


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.tools;
22
23 import com.db4o.ObjectContainer;
24 import com.db4o.events.Event4;
25 import com.db4o.events.EventArgs;
26 import com.db4o.events.EventListener4;
27 import com.db4o.events.EventRegistry;
28 import com.db4o.events.EventRegistryFactory;
29 import com.db4o.foundation.StopWatch;
30
31 /**
32  * Keeps track of query statistics.
33  */
34 public class QueryStats {
35     
36     private EventRegistry _registry = null;
37     
38     private int _activationCount;
39     
40     private final StopWatch _watch = new StopWatch();
41     
42     private final EventListener4 _queryStarted = new EventListener4() {
43         public void onEvent(Event4 e, EventArgs args) {
44             _activationCount = 0;
45             _watch.start();
46         }
47     };
48     
49     private final EventListener4 _queryFinished = new EventListener4() {
50         public void onEvent(Event4 e, EventArgs args) {
51             _watch.stop();
52         }
53     };
54     
55     private final EventListener4 _activated = new EventListener4() {
56         public void onEvent(Event4 e, EventArgs args) {
57             ++_activationCount;
58         };
59     };
60     
61     /**
62      * How long the last query took to execute.
63      *
64      * @return time in miliseconds
65      */
66     public long executionTime() {
67         return _watch.elapsed();
68     }
69     
70     /**
71      * How many objects were activated so far.
72      */
73     public int activationCount() {
74         return _activationCount;
75     }
76
77     /**
78      * Starts gathering query statistics for the specified container.
79      */
80     public void connect(ObjectContainer container) {
81         if (_registry != null) {
82             throw new IllegalArgumentException JavaDoc("Already connected to an ObjectContainer");
83         }
84         _registry = EventRegistryFactory.forObjectContainer(container);
85         _registry.queryStarted().addListener(_queryStarted);
86         _registry.queryFinished().addListener(_queryFinished);
87         _registry.activated().addListener(_activated);
88     }
89     
90     /**
91      * Disconnects from the current container.
92      */
93     public void disconnect() {
94         if (null != _registry) {
95             _registry.queryStarted().removeListener(_queryStarted);
96             _registry.queryFinished().removeListener(_queryFinished);
97             _registry.activated().removeListener(_activated);
98             _registry = null;
99         }
100     }
101 }
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