sdnr/wireless-transport/code-Carbon-SR1/apps/devicemanager/impl/src/main/java/org/opendaylight/mwtn/base/internalTypes/FileWatchdog.java

   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
  18 package org.opendaylight.mwtn.base.internalTypes;
  19
  20 import java.io.File;
  21
  22 import org.slf4j.Logger;
  23 import org.slf4j.LoggerFactory;
  24
  25 /**
  26  * Check every now and then that a certain file has not changed. If it has, then
  27  * call the {@link #doOnChange} method.
  28  *
  29  * @author JunHo Yoon
  30  * @since 3.1.1
  31  */
  32 public abstract class FileWatchdog extends Thread {
  33         private static final Logger LOGGER = LoggerFactory.getLogger(FileWatchdog.class);
  34         /**
  35          * The default delay between every file modification check, set to 60
  36          * seconds.
  37          */
  38         public static final long DEFAULT_DELAY = 60000;
  39         /**
  40          * The name of the file to observe for changes.
  41          */
  42         private String filename;
  43
  44         /**
  45          * The delay to observe between every check. By default set
  46          * {@link #DEFAULT_DELAY}.
  47          */
  48         private long delay = DEFAULT_DELAY;
  49
  50         private File file;
  51         private long lastModified = 0;
  52         private boolean warnedAlready = false;
  53         private boolean interrupted = false;
  54
  55         protected  FileWatchdog(String filename) {
  56                 this.filename = filename;
  57                 file = new File(filename);
  58                 setDaemon(true);
  59                 checkAndConfigure();
  60         }
  61
  62         /**
  63          * Set the delay to observe between each check of the file changes.
  64          *
  65          * @param delay
  66          *            the frequency of file watch.
  67          */
  68         public  void setDelay(long delay) {
  69                 this.delay = delay;
  70         }
  71
  72         /**
  73          * abstract method to be run when the file is changed.
  74          */
  75         protected abstract void doOnChange();
  76
  77         protected  void checkAndConfigure() {
  78                 boolean fileExists;
  79                 try {
  80                         fileExists = file.exists();
  81                 } catch (SecurityException e) {
  82                         LOGGER.warn("Was not allowed to read check file existence, file:[" + filename + "].");
  83                         interrupted = true; // there is no point in continuing
  84                         return;
  85                 }
  86
  87                 if (fileExists) {
  88                         long l = file.lastModified(); // this can also throw a
  89                         if (lastModified ==0) {
  90                                 lastModified = l; // is very unlikely.
  91                         }
  92                         if (l > lastModified) { // however, if we reached this point this
  93                                 lastModified = l; // is very unlikely.
  94                                 doOnChange();
  95                                 warnedAlready = false;
  96                         }
  97                 } else {
  98                         if (!warnedAlready) {
  99                                 LOGGER.debug("[" + filename + "] does not exist.");
 100                                 warnedAlready = true;
 101                         }
 102                 }
 103         }
 104
 105         /*
 106          * (non-Javadoc)
 107          *
 108          * @see java.lang.Thread#run()
 109          */
 110         @Override
 111         public  void run() {
 112                 while (!interrupted && !isInterrupted()) {
 113                         try {
 114                                 Thread.sleep(delay);
 115                         } catch (InterruptedException e) {
 116
 117                         }
 118                         checkAndConfigure();
 119                 }
 120         }
 121 }