Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
BaseInitableBroker |
|
| 5.6;5,6 |
1 | package org.apache.turbine.services; | |
2 | ||
3 | ||
4 | /* | |
5 | * Licensed to the Apache Software Foundation (ASF) under one | |
6 | * or more contributor license agreements. See the NOTICE file | |
7 | * distributed with this work for additional information | |
8 | * regarding copyright ownership. The ASF licenses this file | |
9 | * to you under the Apache License, Version 2.0 (the | |
10 | * "License"); you may not use this file except in compliance | |
11 | * with the License. You may obtain a copy of the License at | |
12 | * | |
13 | * http://www.apache.org/licenses/LICENSE-2.0 | |
14 | * | |
15 | * Unless required by applicable law or agreed to in writing, | |
16 | * software distributed under the License is distributed on an | |
17 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | |
18 | * KIND, either express or implied. See the License for the | |
19 | * specific language governing permissions and limitations | |
20 | * under the License. | |
21 | */ | |
22 | ||
23 | ||
24 | import java.util.Hashtable; | |
25 | import java.util.Stack; | |
26 | ||
27 | import org.apache.commons.logging.Log; | |
28 | import org.apache.commons.logging.LogFactory; | |
29 | ||
30 | /** | |
31 | * A generic implementation of <code>InitableBroker</code>. | |
32 | * Functionality provided by the broker includes: | |
33 | * | |
34 | * <ul> | |
35 | * | |
36 | * <li>Maintaining single instance of each <code>Initable</code> in | |
37 | * the system.</li> | |
38 | * | |
39 | * <li>Early initialization of <code>Initables</code> during system | |
40 | * startup.</li> | |
41 | * | |
42 | * <li>Late initialization of <code>Initables</code> before they are | |
43 | * used.</li> | |
44 | * | |
45 | * <li>Providing instances of <code>Initables</code> to requesting | |
46 | * parties.</li> | |
47 | * | |
48 | * <li>Maintaining dependencies between <code>Initables</code> during | |
49 | * early initalization phases, including circular dependencies | |
50 | * detection.</li> | |
51 | * | |
52 | * </ul> | |
53 | * | |
54 | * @author <a href="mailto:burton@apache.org">Kevin Burton</a> | |
55 | * @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a> | |
56 | * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> | |
57 | * @version $Id: BaseInitableBroker.java 1078552 2011-03-06 19:58:46Z tv $ | |
58 | */ | |
59 | public abstract class BaseInitableBroker | |
60 | implements InitableBroker | |
61 | { | |
62 | /** A repository of Initable instances. */ | |
63 | 0 | protected Hashtable<String, Initable> initables = new Hashtable<String, Initable>(); |
64 | ||
65 | /** | |
66 | * Names of classes being early-initialized are pushed onto this | |
67 | * stack. A name appearing twice indicates a circular dependency | |
68 | * chain. | |
69 | */ | |
70 | 0 | protected Stack<String> stack = new Stack<String>(); |
71 | ||
72 | /** Logging */ | |
73 | 0 | private final Log log = LogFactory.getLog(this.getClass()); |
74 | ||
75 | /** | |
76 | * Default constructor of InitableBroker. | |
77 | * | |
78 | * This constructor does nothing. Your brokers should be | |
79 | * singletons, therefore their constructors should be | |
80 | * private. They should also have public YourBroker getInstance() | |
81 | * methods. | |
82 | */ | |
83 | protected BaseInitableBroker() | |
84 | 0 | { |
85 | // empty | |
86 | 0 | } |
87 | ||
88 | /** | |
89 | * Performs early initialization of an Initable class. | |
90 | * | |
91 | * @param className The name of the class to be initialized. | |
92 | * @param data An Object to be used for initialization activities. | |
93 | * @exception InitializationException Initialization was not successful. | |
94 | */ | |
95 | public void initClass(String className, Object data) | |
96 | throws InitializationException | |
97 | { | |
98 | // make sure that only one thread calls this method recursively | |
99 | 0 | synchronized (stack) |
100 | { | |
101 | 0 | int pos = stack.search(className); |
102 | 0 | if (pos != -1) |
103 | { | |
104 | 0 | StringBuffer msg = new StringBuffer().append(className) |
105 | .append(" couldn't be initialized because of circular depency chain:\n"); | |
106 | 0 | for (int i = pos; i > 0; i--) |
107 | { | |
108 | 0 | msg.append(stack.elementAt(stack.size() - i - 1) + "->"); |
109 | } | |
110 | 0 | msg.append(className).append('\n'); |
111 | ||
112 | 0 | throw new InitializationException(msg.toString()); |
113 | } | |
114 | try | |
115 | { | |
116 | 0 | stack.push(className); |
117 | 0 | Initable instance = getInitableInstance(className); |
118 | 0 | if (!instance.getInit()) |
119 | { | |
120 | // this call might result in an indirect recursion | |
121 | 0 | instance.init(data); |
122 | } | |
123 | } | |
124 | finally | |
125 | { | |
126 | // Succeeded or not, make sure the name gets off the stack. | |
127 | 0 | stack.pop(); |
128 | 0 | } |
129 | 0 | } |
130 | 0 | } |
131 | ||
132 | /** | |
133 | * Shuts down an <code>Initable</code>. | |
134 | * | |
135 | * This method is used to release resources allocated by an | |
136 | * <code>Initable</code>, and return it to its initial (uninitailized) | |
137 | * state. | |
138 | * | |
139 | * @param className The name of the class to be uninitialized. | |
140 | */ | |
141 | public void shutdownClass(String className) | |
142 | { | |
143 | try | |
144 | { | |
145 | 0 | Initable initable = getInitableInstance(className); |
146 | 0 | if (initable.getInit()) |
147 | { | |
148 | 0 | initable.shutdown(); |
149 | 0 | ((BaseInitable) initable).setInit(false); |
150 | } | |
151 | } | |
152 | 0 | catch (InstantiationException e) |
153 | { | |
154 | // Shutdown of a nonexistent class was requested. | |
155 | // This does not hurt anything, so we log the error and continue. | |
156 | 0 | log.error("Shutdown of a nonexistent class " + |
157 | className + " was requested", e); | |
158 | 0 | } |
159 | 0 | } |
160 | ||
161 | /** | |
162 | * Provides an instance of Initable class ready to work. | |
163 | * | |
164 | * If the requested class couldn't be instatiated or initialized, | |
165 | * an InstantiationException will be thrown. You needn't handle | |
166 | * this exception in your code, since it indicates fatal | |
167 | * misconfigurtion of the system. | |
168 | * | |
169 | * @param className The name of the Initable requested. | |
170 | * @return An instance of the requested Initable. | |
171 | * @exception InstantiationException if there was a problem | |
172 | * during instantiation or initialization of the Initable. | |
173 | */ | |
174 | public Initable getInitable(String className) | |
175 | throws InstantiationException | |
176 | { | |
177 | Initable initable; | |
178 | try | |
179 | { | |
180 | 0 | initable = getInitableInstance(className); |
181 | 0 | if (!initable.getInit()) |
182 | { | |
183 | 0 | synchronized (initable.getClass()) |
184 | { | |
185 | 0 | if (!initable.getInit()) |
186 | { | |
187 | 0 | initable.init(); |
188 | } | |
189 | 0 | if (!initable.getInit()) |
190 | { | |
191 | // this exception will be caught & rethrown by this | |
192 | // very method. getInit() returning false indicates | |
193 | // some initialization issue, which in turn prevents | |
194 | // the InitableBroker from passing a working | |
195 | // instance of the initable to the client. | |
196 | 0 | throw new InitializationException( |
197 | "init() failed to initialize class " | |
198 | + className); | |
199 | } | |
200 | 0 | } |
201 | } | |
202 | 0 | return initable; |
203 | } | |
204 | 0 | catch (InitializationException e) |
205 | { | |
206 | 0 | throw new InstantiationException("Class " + className + |
207 | " failed to initialize", e); | |
208 | } | |
209 | } | |
210 | ||
211 | /** | |
212 | * Retrieves an instance of an Initable from the repository. | |
213 | * | |
214 | * If the requested class is not present in the repository, it is | |
215 | * instantiated and passed a reference to the broker, saved and | |
216 | * then returned. | |
217 | * | |
218 | * @param className The name of the class to be instantiated. | |
219 | * @exception InstantiationException if the requested class can't | |
220 | * be instantiated. | |
221 | */ | |
222 | protected Initable getInitableInstance(String className) | |
223 | throws InstantiationException | |
224 | { | |
225 | 0 | Initable initable = initables.get(className); |
226 | ||
227 | 0 | if (initable == null) |
228 | { | |
229 | try | |
230 | { | |
231 | 0 | initable = (Initable) Class.forName(className).newInstance(); |
232 | } | |
233 | ||
234 | // those two errors must be passed to the VM | |
235 | 0 | catch (ThreadDeath t) |
236 | { | |
237 | 0 | throw t; |
238 | } | |
239 | 0 | catch (OutOfMemoryError t) |
240 | { | |
241 | 0 | throw t; |
242 | } | |
243 | ||
244 | 0 | catch (Throwable t) |
245 | { | |
246 | // Used to indicate error condition. | |
247 | 0 | String msg = null; |
248 | ||
249 | 0 | if (t instanceof NoClassDefFoundError) |
250 | { | |
251 | 0 | msg = "A class referenced by " + className + |
252 | " is unavailable. Check your jars and classes."; | |
253 | } | |
254 | 0 | else if (t instanceof ClassNotFoundException) |
255 | { | |
256 | 0 | msg = "Class " + className + |
257 | " is unavailable. Check your jars and classes."; | |
258 | } | |
259 | 0 | else if (t instanceof ClassCastException) |
260 | { | |
261 | 0 | msg = "Class " + className + |
262 | " doesn't implement Initable."; | |
263 | } | |
264 | else | |
265 | { | |
266 | 0 | msg = "Failed to instantiate " + className; |
267 | } | |
268 | ||
269 | 0 | throw new InstantiationException(msg, t); |
270 | 0 | } |
271 | ||
272 | 0 | initable.setInitableBroker(this); |
273 | 0 | initables.put(className, initable); |
274 | } | |
275 | ||
276 | 0 | return initable; |
277 | } | |
278 | ||
279 | } |