Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
PoolableObjectFactory |
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| 1.0;1 |
1 | /* | |
2 | * Licensed to the Apache Software Foundation (ASF) under one or more | |
3 | * contributor license agreements. See the NOTICE file distributed with | |
4 | * this work for additional information regarding copyright ownership. | |
5 | * The ASF licenses this file to You under the Apache License, Version 2.0 | |
6 | * (the "License"); you may not use this file except in compliance with | |
7 | * the License. You may obtain a copy of the License at | |
8 | * | |
9 | * http://www.apache.org/licenses/LICENSE-2.0 | |
10 | * | |
11 | * Unless required by applicable law or agreed to in writing, software | |
12 | * distributed under the License is distributed on an "AS IS" BASIS, | |
13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
14 | * See the License for the specific language governing permissions and | |
15 | * limitations under the License. | |
16 | */ | |
17 | ||
18 | package org.apache.commons.pool; | |
19 | ||
20 | /** | |
21 | * An interface defining life-cycle methods for | |
22 | * instances to be served by an {@link ObjectPool}. | |
23 | * <p> | |
24 | * By contract, when an {@link ObjectPool} | |
25 | * delegates to a {@link PoolableObjectFactory}, | |
26 | * <ol> | |
27 | * <li> | |
28 | * {@link #makeObject makeObject} | |
29 | * is called whenever a new instance is needed. | |
30 | * </li> | |
31 | * <li> | |
32 | * {@link #activateObject activateObject} | |
33 | * is invoked on every instance that has been | |
34 | * {@link #passivateObject passivated} before it is | |
35 | * {@link ObjectPool#borrowObject borrowed} from the pool. | |
36 | * </li> | |
37 | * <li> | |
38 | * {@link #validateObject validateObject} | |
39 | * is invoked on {@link #activateObject activated} instances to make sure | |
40 | * they can be {@link ObjectPool#borrowObject borrowed} from the pool. | |
41 | * <code>validateObject</code> <strong>may</strong> also be used to test an | |
42 | * instance being {@link ObjectPool#returnObject returned} to the pool | |
43 | * before it is {@link #passivateObject passivated}. It will only be invoked | |
44 | * on an activated instance. | |
45 | * </li> | |
46 | * <li> | |
47 | * {@link #passivateObject passivateObject} | |
48 | * is invoked on every instance when it is returned to the pool. | |
49 | * </li> | |
50 | * <li> | |
51 | * {@link #destroyObject destroyObject} | |
52 | * is invoked on every instance when it is being "dropped" from the | |
53 | * pool (whether due to the response from <code>validateObject</code>, | |
54 | * or for reasons specific to the pool implementation.) There is no | |
55 | * guarantee that the instance being destroyed will | |
56 | * be considered active, passive or in a generally consistent state. | |
57 | * </li> | |
58 | * </ol> | |
59 | * </p> | |
60 | * <p> | |
61 | * {@link PoolableObjectFactory} must be thread-safe. The only promise | |
62 | * an {@link ObjectPool} makes is that the same instance of an object will not | |
63 | * be passed to more than one method of a <code>PoolableObjectFactory</code> | |
64 | * at a time. | |
65 | * </p> | |
66 | * | |
67 | * @see ObjectPool | |
68 | * | |
69 | * @author Rodney Waldhoff | |
70 | * @author Sandy McArthur | |
71 | * @version $Revision: 777748 $ $Date: 2009-05-22 20:00:44 -0400 (Fri, 22 May 2009) $ | |
72 | * @since Pool 1.0 | |
73 | */ | |
74 | public interface PoolableObjectFactory { | |
75 | /** | |
76 | * Creates an instance that can be served by the pool. | |
77 | * Instances returned from this method should be in the | |
78 | * same state as if they had been | |
79 | * {@link #activateObject activated}. They will not be | |
80 | * activated before being served by the pool. | |
81 | * | |
82 | * @return an instance that can be served by the pool. | |
83 | * @throws Exception if there is a problem creating a new instance, | |
84 | * this will be propagated to the code requesting an object. | |
85 | */ | |
86 | Object makeObject() throws Exception; | |
87 | ||
88 | /** | |
89 | * Destroys an instance no longer needed by the pool. | |
90 | * <p> | |
91 | * It is important for implementations of this method to be aware | |
92 | * that there is no guarantee about what state <code>obj</code> | |
93 | * will be in and the implementation should be prepared to handle | |
94 | * unexpected errors. | |
95 | * </p> | |
96 | * <p> | |
97 | * Also, an implementation must take in to consideration that | |
98 | * instances lost to the garbage collector may never be destroyed. | |
99 | * </p> | |
100 | * | |
101 | * @param obj the instance to be destroyed | |
102 | * @throws Exception should be avoided as it may be swallowed by | |
103 | * the pool implementation. | |
104 | * @see #validateObject | |
105 | * @see ObjectPool#invalidateObject | |
106 | */ | |
107 | void destroyObject(Object obj) throws Exception; | |
108 | ||
109 | /** | |
110 | * Ensures that the instance is safe to be returned by the pool. | |
111 | * Returns <code>false</code> if <code>obj</code> should be destroyed. | |
112 | * | |
113 | * @param obj the instance to be validated | |
114 | * @return <code>false</code> if <code>obj</code> is not valid and should | |
115 | * be dropped from the pool, <code>true</code> otherwise. | |
116 | */ | |
117 | boolean validateObject(Object obj); | |
118 | ||
119 | /** | |
120 | * Reinitialize an instance to be returned by the pool. | |
121 | * | |
122 | * @param obj the instance to be activated | |
123 | * @throws Exception if there is a problem activating <code>obj</code>, | |
124 | * this exception may be swallowed by the pool. | |
125 | * @see #destroyObject | |
126 | */ | |
127 | void activateObject(Object obj) throws Exception; | |
128 | ||
129 | /** | |
130 | * Uninitialize an instance to be returned to the idle object pool. | |
131 | * | |
132 | * @param obj the instance to be passivated | |
133 | * @throws Exception if there is a problem passivating <code>obj</code>, | |
134 | * this exception may be swallowed by the pool. | |
135 | * @see #destroyObject | |
136 | */ | |
137 | void passivateObject(Object obj) throws Exception; | |
138 | } |