JAL-3026 srcjar files for VARNA and log4j

[jalview.git] / srcjar / org / apache / log4j / helpers / FileWatchdog.java

diff --git a/srcjar/org/apache/log4j/helpers/FileWatchdog.java b/srcjar/org/apache/log4j/helpers/FileWatchdog.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Contributors:  Mathias Bogaert
+
+package org.apache.log4j.helpers;
+
+import java.io.File;
+
+/**
+   Check every now and then that a certain file has not changed. If it
+   has, then call the {@link #doOnChange} method.
+
+
+   @author Ceki Gülcü
+   @since version 0.9.1 */
+public abstract class FileWatchdog extends Thread {
+
+  /**
+     The default delay between every file modification check, set to 60
+     seconds.  */
+  static final public long DEFAULT_DELAY = 60000; 
+  /**
+     The name of the file to observe  for changes.
+   */
+  protected String filename;
+  
+  /**
+     The delay to observe between every check. By default set {@link
+     #DEFAULT_DELAY}. */
+  protected long delay = DEFAULT_DELAY; 
+  
+  File file;
+  long lastModif = 0; 
+  boolean warnedAlready = false;
+  boolean interrupted = false;
+
+  protected
+  FileWatchdog(String filename) {
+    super("FileWatchdog");
+    this.filename = filename;
+    file = new File(filename);
+    setDaemon(true);
+    checkAndConfigure();
+  }
+
+  /**
+     Set the delay to observe between each check of the file changes.
+   */
+  public
+  void setDelay(long delay) {
+    this.delay = delay;
+  }
+
+  abstract 
+  protected 
+  void doOnChange();
+
+  protected
+  void checkAndConfigure() {
+    boolean fileExists;
+    try {
+      fileExists = file.exists();
+    } catch(SecurityException  e) {
+      LogLog.warn("Was not allowed to read check file existance, file:["+
+                 filename+"].");
+      interrupted = true; // there is no point in continuing
+      return;
+    }
+
+    if(fileExists) {
+      long l = file.lastModified(); // this can also throw a SecurityException
+      if(l > lastModif) {           // however, if we reached this point this
+       lastModif = l;              // is very unlikely.
+       doOnChange();
+       warnedAlready = false;
+      }
+    } else {
+      if(!warnedAlready) {
+       LogLog.debug("["+filename+"] does not exist.");
+       warnedAlready = true;
+      }
+    }
+  }
+
+  public
+  void run() {    
+    while(!interrupted) {
+      try {
+           Thread.sleep(delay);
+      } catch(InterruptedException e) {
+       // no interruption expected
+      }
+      checkAndConfigure();
+    }
+  }
+}