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Java > Open Source Codes > org > apache > commons > pool > KeyedObjectPool


1 /*
2  * Copyright 1999-2004 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
17 package org.apache.commons.pool;
18
19 /**
20  * A "keyed" pooling interface.
21  * <p>
22  * A keyed pool pools instances of multiple types. Each
23  * type may be accessed using an arbitrary key.
24  * <p>
25  * Example of use:
26  * <table border="1" cellspacing="0" cellpadding="3" align="center" bgcolor="#FFFFFF"><tr><td><pre>
27  * Object obj = <font color="#0000CC">null</font>;
28  * Object key = <font color="#CC0000">"Key"</font>;
29  *
30  * <font color="#0000CC">try</font> {
31  * obj = pool.borrowObject(key);
32  * <font color="#00CC00">//...use the object...</font>
33  * } <font color="#0000CC">catch</font>(Exception e) {
34  * <font color="#00CC00">//...handle any exceptions...</font>
35  * } <font color="#0000CC">finally</font> {
36  * <font color="#00CC00">// make sure the object is returned to the pool</font>
37  * <font color="#0000CC">if</font>(<font color="#0000CC">null</font> != obj) {
38  * pool.returnObject(key,obj);
39  * }
40  * }</pre></td></tr></table>
41  *
42  * <p>
43  * {@link KeyedObjectPool} implementations <i>may</i> choose to store at most
44  * one instance per key value, or may choose to maintain a pool of instances
45  * for each key (essentially creating a {@link java.util.Map Map} of
46  * {@link ObjectPool pools}).
47  * </p>
48  *
49  * @see KeyedPoolableObjectFactory
50  * @see KeyedObjectPoolFactory
51  * @see ObjectPool
52  *
53  * @author Rodney Waldhoff
54  * @version $Revision$ $Date: 2005-02-26 05:13:28 -0800 (Sat, 26 Feb 2005) $
55  */
56 public interface KeyedObjectPool {
57     /**
58      * Obtain an instance from my pool
59      * for the specified <i>key</i>.
60      * By contract, clients MUST return
61      * the borrowed object using
62      * {@link #returnObject(java.lang.Object,java.lang.Object) <tt>returnObject</tt>},
63      * or a related method as defined in an implementation
64      * or sub-interface,
65      * using a <i>key</i> that is equivalent to the one used to
66      * borrow the instance in the first place.
67      *
68      * @param key the key used to obtain the object
69      * @return an instance from my pool.
70      */
71     Object JavaDoc borrowObject(Object JavaDoc key) throws Exception JavaDoc;
72
73     /**
74      * Return an instance to my pool.
75      * By contract, <i>obj</i> MUST have been obtained
76      * using {@link #borrowObject(java.lang.Object) <tt>borrowObject</tt>}
77      * or a related method as defined in an implementation
78      * or sub-interface
79      * using a <i>key</i> that is equivalent to the one used to
80      * borrow the <tt>Object</tt> in the first place.
81      *
82      * @param key the key used to obtain the object
83      * @param obj a {@link #borrowObject(java.lang.Object) borrowed} instance to be returned.
84      */
85     void returnObject(Object JavaDoc key, Object JavaDoc obj) throws Exception JavaDoc;
86
87     /**
88      * Invalidates an object from the pool
89      * By contract, <i>obj</i> MUST have been obtained
90      * using {@link #borrowObject borrowObject}
91      * or a related method as defined in an implementation
92      * or sub-interface
93      * using a <i>key</i> that is equivalent to the one used to
94      * borrow the <tt>Object</tt> in the first place.
95      * <p>
96      * This method should be used when an object that has been borrowed
97      * is determined (due to an exception or other problem) to be invalid.
98      * If the connection should be validated before or after borrowing,
99      * then the {@link PoolableObjectFactory#validateObject} method should be
100      * used instead.
101      *
102      * @param obj a {@link #borrowObject borrowed} instance to be returned.
103      */
104     void invalidateObject(Object JavaDoc key, Object JavaDoc obj) throws Exception JavaDoc;
105
106     /**
107      * Create an object using my {@link #setFactory factory} or other
108      * implementation dependent mechanism, and place it into the pool.
109      * addObject() is useful for "pre-loading" a pool with idle objects.
110      * (Optional operation).
111      */
112     void addObject(Object JavaDoc key) throws Exception JavaDoc;
113
114     /**
115      * Returns the number of instances
116      * corresponding to the given <i>key</i>
117      * currently idle in my pool (optional operation).
118      * Throws {@link UnsupportedOperationException}
119      * if this information is not available.
120      *
121      * @param key the key
122      * @return the number of instances corresponding to the given <i>key</i> currently idle in my pool
123      * @throws UnsupportedOperationException when this implementation doesn't support the operation
124      */
125     int getNumIdle(Object JavaDoc key) throws UnsupportedOperationException JavaDoc;
126
127     /**
128      * Returns the number of instances
129      * currently borrowed from but not yet returned
130      * to my pool corresponding to the
131      * given <i>key</i> (optional operation).
132      * Throws {@link UnsupportedOperationException}
133      * if this information is not available.
134      *
135      * @param key the key
136      * @return the number of instances corresponding to the given <i>key</i> currently borrowed in my pool
137      * @throws UnsupportedOperationException when this implementation doesn't support the operation
138      */
139     int getNumActive(Object JavaDoc key) throws UnsupportedOperationException JavaDoc;
140
141     /**
142      * Returns the total number of instances
143      * currently idle in my pool (optional operation).
144      * Throws {@link UnsupportedOperationException}
145      * if this information is not available.
146      *
147      * @return the total number of instances currently idle in my pool
148      * @throws UnsupportedOperationException when this implementation doesn't support the operation
149      */
150     int getNumIdle() throws UnsupportedOperationException JavaDoc;
151
152     /**
153      * Returns the total number of instances
154      * current borrowed from my pool but not
155      * yet returned (optional operation).
156      * Throws {@link UnsupportedOperationException}
157      * if this information is not available.
158      *
159      * @return the total number of instances currently borrowed from my pool
160      * @throws UnsupportedOperationException when this implementation doesn't support the operation
161      */
162     int getNumActive() throws UnsupportedOperationException JavaDoc;
163
164     /**
165      * Clears my pool, removing all pooled instances
166      * (optional operation).
167      * Throws {@link UnsupportedOperationException}
168      * if the pool cannot be cleared.
169      * @throws UnsupportedOperationException when this implementation doesn't support the operation
170      */
171     void clear() throws Exception JavaDoc, UnsupportedOperationException JavaDoc;
172
173     /**
174      * Clears the specified pool, removing all
175      * pooled instances corresponding to
176      * the given <i>key</i> (optional operation).
177      * Throws {@link UnsupportedOperationException}
178      * if the pool cannot be cleared.
179      * @param key the key to clear
180      * @throws UnsupportedOperationException when this implementation doesn't support the operation
181      */
182     void clear(Object JavaDoc key) throws Exception JavaDoc, UnsupportedOperationException JavaDoc;
183
184     /**
185      * Close this pool, and free any resources associated with it.
186      */
187     void close() throws Exception JavaDoc;
188
189     /**
190      * Sets the {@link KeyedPoolableObjectFactory factory} I use
191      * to create new instances (optional operation).
192      * @param factory the {@link KeyedPoolableObjectFactory} I use to create new instances.
193      * @throws IllegalStateException when the factory cannot be set at this time
194      * @throws UnsupportedOperationException when this implementation doesn't support the operation
195      */
196     void setFactory(KeyedPoolableObjectFactory factory) throws IllegalStateException JavaDoc, UnsupportedOperationException JavaDoc;
197 }
198
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