| 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 | } |