Coverage Report - org.apache.turbine.services.BaseInitableBroker
 
Classes in this File Line Coverage Branch Coverage Complexity
BaseInitableBroker
0%
0/61
0%
0/22
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  
 }