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 package org.apache.commons.pool2;
18
19 /**
20 * An interface defining life-cycle methods for
21 * instances to be served by a {@link KeyedObjectPool}.
22 * <p>
23 * By contract, when an {@link KeyedObjectPool}
24 * delegates to a {@link KeyedPooledObjectFactory},
25 * </p>
26 * <ol>
27 * <li>
28 * {@link #makeObject} is called whenever a new instance is needed.
29 * </li>
30 * <li>
31 * {@link #activateObject} is invoked on every instance that has been
32 * {@link #passivateObject passivated} before it is
33 * {@link KeyedObjectPool#borrowObject borrowed} from the pool.
34 * </li>
35 * <li>
36 * {@link #validateObject} may be invoked on {@link #activateObject activated}
37 * instances to make sure they can be
38 * {@link KeyedObjectPool#borrowObject borrowed} from the pool.
39 * {@code validateObject} may also be used to test an
40 * instance being {@link KeyedObjectPool#returnObject returned} to the pool
41 * before it is {@link #passivateObject passivated}. It will only be invoked
42 * on an activated instance.
43 * </li>
44 * <li>
45 * {@link #passivateObject passivateObject}
46 * is invoked on every instance when it is returned to the pool.
47 * </li>
48 * <li>
49 * {@link #destroyObject destroyObject}
50 * is invoked on every instance when it is being "dropped" from the
51 * pool (whether due to the response from {@code validateObject},
52 * or for reasons specific to the pool implementation.) There is no
53 * guarantee that the instance being destroyed will
54 * be considered active, passive or in a generally consistent state.
55 * </li>
56 * </ol>
57 * {@link KeyedPooledObjectFactory} must be thread-safe. The only promise
58 * an {@link KeyedObjectPool} makes is that the same instance of an object will
59 * not be passed to more than one method of a
60 * {@code KeyedPooledObjectFactory} at a time.
61 * <p>
62 * While clients of a {@link KeyedObjectPool} borrow and return instances of
63 * the underlying value type V, the factory methods act on instances of
64 * {@link PooledObject PooledObject<V>}. These are the object wrappers that
65 * pools use to track and maintain state informations about the objects that
66 * they manage.
67 * </p>
68 *
69 * @see KeyedObjectPool
70 * @see BaseKeyedPooledObjectFactory
71 *
72 * @param <K> The type of keys managed by this factory.
73 * @param <V> Type of element managed by this factory.
74 *
75 * @since 2.0
76 */
77 public interface KeyedPooledObjectFactory<K, V> {
78
79 /**
80 * Reinitializes an instance to be returned by the pool.
81 *
82 * @param key the key used when selecting the object
83 * @param p a {@code PooledObject} wrapping the instance to be activated
84 *
85 * @throws Exception if there is a problem activating {@code obj},
86 * this exception may be swallowed by the pool.
87 *
88 * @see #destroyObject
89 */
90 void activateObject(K key, PooledObject<V> p) throws Exception;
91
92 /**
93 * Destroys an instance no longer needed by the pool.
94 * <p>
95 * It is important for implementations of this method to be aware that there
96 * is no guarantee about what state {@code obj} will be in and the
97 * implementation should be prepared to handle unexpected errors.
98 * </p>
99 * <p>
100 * Also, an implementation must take in to consideration that instances lost
101 * to the garbage collector may never be destroyed.
102 * </p>
103 *
104 * @param key the key used when selecting the instance
105 * @param p a {@code PooledObject} wrapping the instance to be destroyed
106 *
107 * @throws Exception should be avoided as it may be swallowed by
108 * the pool implementation.
109 *
110 * @see #validateObject
111 * @see KeyedObjectPool#invalidateObject
112 */
113 void destroyObject(K key, PooledObject<V> p) throws Exception;
114
115 /**
116 * Destroys an instance no longer needed by the pool, using the provided {@link DestroyMode}.
117 *
118 * @param key the key used when selecting the instance
119 * @param p a {@code PooledObject} wrapping the instance to be destroyed
120 * @param destroyMode DestroyMode providing context to the factory
121 *
122 * @throws Exception should be avoided as it may be swallowed by
123 * the pool implementation.
124 *
125 * @see #validateObject
126 * @see KeyedObjectPool#invalidateObject
127 * @see #destroyObject(Object, PooledObject)
128 * @see DestroyMode
129 * @since 2.9.0
130 */
131 default void destroyObject(final K key, final PooledObject<V> p, final DestroyMode destroyMode) throws Exception {
132 destroyObject(key, p);
133 }
134
135 /**
136 * Creates an instance that can be served by the pool and
137 * wrap it in a {@link PooledObject} to be managed by the pool.
138 *
139 * @param key the key used when constructing the object
140 *
141 * @return a {@code PooledObject} wrapping an instance that can
142 * be served by the pool.
143 *
144 * @throws Exception if there is a problem creating a new instance,
145 * this will be propagated to the code requesting an object.
146 */
147 PooledObject<V> makeObject(K key) throws Exception;
148
149 /**
150 * Uninitializes an instance to be returned to the idle object pool.
151 *
152 * @param key the key used when selecting the object
153 * @param p a {@code PooledObject} wrapping the instance to be passivated
154 *
155 * @throws Exception if there is a problem passivating {@code obj},
156 * this exception may be swallowed by the pool.
157 *
158 * @see #destroyObject
159 */
160 void passivateObject(K key, PooledObject<V> p) throws Exception;
161
162 /**
163 * Ensures that the instance is safe to be returned by the pool.
164 *
165 * @param key the key used when selecting the object
166 * @param p a {@code PooledObject} wrapping the instance to be validated
167 *
168 * @return {@code false} if {@code obj} is not valid and should
169 * be dropped from the pool, {@code true} otherwise.
170 */
171 boolean validateObject(K key, PooledObject<V> p);
172 }
173