PoolService


1   package org.apache.turbine.services.pool;
2   
3   /*
4    * Copyright 2001-2004 The Apache Software Foundation.
5    *
6    * Licensed under the Apache License, Version 2.0 (the "License")
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import org.apache.turbine.services.Service;
20  import org.apache.turbine.util.TurbineException;
21  
22  /**
23   * The Pool Service extends the Factory Service by adding support
24   * for pooling instantiated objects. When a new instance is
25   * requested, the service first checks its pool if one is available.
26   * If the the pool is empty, a new object will be instantiated
27   * from the specified class. If only class name is given, the request
28   * to create an intance will be forwarded to the Factory Service.
29   *
30   * <p>For objects implementing the Recyclable interface, a recycle
31   * method will be called, when they are taken from the pool, and
32   * a dispose method, when they are returned to the pool.
33   *
34   * @author <a HREF="mailto:ilkka.priha@simsoft.fi">Ilkka Priha</a>
35   * @version $Id: PoolService.java,v 1.7.2.2 2004/05/20 03:06:52 seade Exp $
36   */
37  public interface PoolService
38          extends Service
39  {
40      /** The key under which this service is stored in TurbineServices. */
41      String   SERVICE_NAME = "PoolService";
42      
43      /** The default pool capacity. */
44      int DEFAULT_POOL_CAPACITY = 128;
45      
46      /** The name of the pool capacity property */
47      String   POOL_CAPACITY_KEY = "pool.capacity";
48      
49      /** Are we running in debug mode? */
50      String   POOL_DEBUG_KEY = "pool.debug";
51  
52      /** Default Value for debug mode */
53      boolean POOL_DEBUG_DEFAULT = false;
54  
55      /**
56       * Gets an instance of a named class.
57       *
58       * @param className the name of the class.
59       * @return the instance.
60       * @throws TurbineException if instantiation fails.
61       */
62      Object   getInstance(String   className)
63              throws TurbineException;
64  
65      /**
66       * Gets an instance of a named class using a specified class loader.
67       *
68       * <p>Class loaders are supported only if the isLoaderSupported
69       * method returns true. Otherwise the loader parameter is ignored.
70       *
71       * @param className the name of the class.
72       * @param loader the class loader.
73       * @return the instance.
74       * @throws TurbineException if instantiation fails.
75       */
76      Object   getInstance(String   className,
77              ClassLoader   loader)
78              throws TurbineException;
79  
80      /**
81       * Gets an instance of a named class.
82       * Parameters for its constructor are given as an array of objects,
83       * primitive types must be wrapped with a corresponding class.
84       *
85       * @param className the name of the class.
86       * @param params an array containing the parameters of the constructor.
87       * @param signature an array containing the signature of the constructor.
88       * @return the instance.
89       * @throws TurbineException if instantiation fails.
90       */
91      Object   getInstance(String   className,
92              Object  [] params,
93              String  [] signature)
94              throws TurbineException;
95  
96      /**
97       * Gets an instance of a named class using a specified class loader.
98       * Parameters for its constructor are given as an array of objects,
99       * primitive types must be wrapped with a corresponding class.
100      *
101      * <p>Class loaders are supported only if the isLoaderSupported
102      * method returns true. Otherwise the loader parameter is ignored.
103      *
104      * @param className the name of the class.
105      * @param loader the class loader.
106      * @param params an array containing the parameters of the constructor.
107      * @param signature an array containing the signature of the constructor.
108      * @return the instance.
109      * @throws TurbineException if instantiation fails.
110      */
111     Object   getInstance(String   className,
112             ClassLoader   loader,
113             Object  [] params,
114             String  [] signature)
115             throws TurbineException;
116 
117     /**
118      * Tests if specified class loaders are supported for a named class.
119      *
120      * @param className the name of the class.
121      * @return true if class loaders are supported, false otherwise.
122      * @throws TurbineException if test fails.
123      * @deprecated Use TurbineFactory.isLoaderSupported(className)
124      */
125     boolean isLoaderSupported(String   className)
126             throws TurbineException;
127 
128     /**
129      * Gets an instance of a specified class either from the pool
130      * or by instatiating from the class if the pool is empty.
131      *
132      * @param clazz the class.
133      * @return the instance.
134      * @throws TurbineException if recycling fails.
135      */
136     Object   getInstance(Class   clazz)
137             throws TurbineException;
138 
139     /**
140      * Gets an instance of a specified class either from the pool
141      * or by instatiating from the class if the pool is empty.
142      *
143      * @param clazz the class.
144      * @param params an array containing the parameters of the constructor.
145      * @param signature an array containing the signature of the constructor.
146      * @return the instance.
147      * @throws TurbineException if recycling fails.
148      */
149     Object   getInstance(Class   clazz,
150             Object   params[],
151             String   signature[])
152             throws TurbineException;
153 
154     /**
155      * Puts a used object back to the pool. Objects implementing
156      * the Recyclable interface can provide a recycle method to
157      * be called when they are reused and a dispose method to be
158      * called when they are returned to the pool.
159      *
160      * @param instance the object instance to recycle.
161      * @return true if the instance was accepted.
162      */
163     boolean putInstance(Object   instance);
164 
165     /**
166      * Gets the capacity of the pool for a named class.
167      *
168      * @param className the name of the class.
169      */
170     int getCapacity(String   className);
171 
172     /**
173      * Sets the capacity of the pool for a named class.
174      * Note that the pool will be cleared after the change.
175      *
176      * @param className the name of the class.
177      * @param capacity the new capacity.
178      */
179     void setCapacity(String   className,
180                      int capacity);
181 
182     /**
183      * Gets the current size of the pool for a named class.
184      *
185      * @param className the name of the class.
186      */
187     int getSize(String   className);
188 
189     /**
190      * Clears instances of a named class from the pool.
191      *
192      * @param className the name of the class.
193      */
194     void clearPool(String   className);
195 
196     /**
197      * Clears all instances from the pool.
198      */
199     void clearPool();
200 
201 }
202
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