org.apache.commons.io.input
Class Tailer

java.lang.Object
  org.apache.commons.io.input.Tailer

All Implemented Interfaces:

Runnable

public class Tailer
extends Object
implements Runnable

Simple implementation of the unix "tail -f" functionality.

1. Create a TailerListener implementation

First you need to create a TailerListener implementation (TailerListenerAdapter is provided for convenience so that you don't have to implement every method).

For example:

  public class MyTailerListener extends TailerListenerAdapter {
      public void handle(String line) {
          System.out.println(line);
      }
  }
 

2. Using a Tailer

You can create and use a Tailer in one of three ways:

• Using one of the static helper methods:
  • create(File, TailerListener)
  • create(File, TailerListener, long)
  • create(File, TailerListener, long, boolean)
• Using an Executor
• Using an Thread

An example of each of these is shown below.

2.1 Using the static helper method

      TailerListener listener = new MyTailerListener();
      Tailer tailer = Tailer.create(file, listener, delay);
 

2.2 Use an Executor

      TailerListener listener = new MyTailerListener();
      Tailer tailer = new Tailer(file, listener, delay);

      // stupid executor impl. for demo purposes
      Executor executor = new Executor() {
          public void execute(Runnable command) {
              command.run();
           }
      };

      executor.execute(tailer);
 

2.3 Use a Thread

      TailerListener listener = new MyTailerListener();
      Tailer tailer = new Tailer(file, listener, delay);
      Thread thread = new Thread(tailer);
      thread.setDaemon(true); // optional
      thread.start();
 

3. Stop Tailing

Remember to stop the tailer when you have done with it:

      tailer.stop();
 

Since:

2.0

Version:

$Id: Tailer.java 1304052 2012-03-22 20:55:29Z ggregory $

See Also:

TailerListener, TailerListenerAdapter

Constructor Summary

Tailer(File file, TailerListener listener)
Creates a Tailer for the given file, starting from the beginning, with the default delay of 1.0s.

Tailer(File file, TailerListener listener, long delay)
Creates a Tailer for the given file, starting from the beginning.

Tailer(File file, TailerListener listener, long delay, boolean end)
Creates a Tailer for the given file, with a delay other than the default 1.0s.

Method Summary

static Tailer	create(File file, TailerListener listener) Creates and starts a Tailer for the given file, starting at the beginning of the file with the default delay of 1.0s
static Tailer	create(File file, TailerListener listener, long delay) Creates and starts a Tailer for the given file, starting at the beginning of the file
static Tailer	create(File file, TailerListener listener, long delay, boolean end) Creates and starts a Tailer for the given file.
long	getDelay() Return the delay.
File	getFile() Return the file.
void	run() Follows changes in the file, calling the TailerListener's handle method for each new line.
void	stop() Allows the tailer to complete its current loop and return.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Tailer

public Tailer(File file,
              TailerListener listener)

Creates a Tailer for the given file, starting from the beginning, with the default delay of 1.0s.

Parameters:

file - The file to follow.

listener - the TailerListener to use.

Tailer

public Tailer(File file,
              TailerListener listener,
              long delay)

Creates a Tailer for the given file, starting from the beginning.

Parameters:

file - the file to follow.

listener - the TailerListener to use.

delay - the delay between checks of the file for new content in milliseconds.

Tailer

public Tailer(File file,
              TailerListener listener,
              long delay,
              boolean end)

Creates a Tailer for the given file, with a delay other than the default 1.0s.

Parameters:

file - the file to follow.

listener - the TailerListener to use.

delay - the delay between checks of the file for new content in milliseconds.

end - Set to true to tail from the end of the file, false to tail from the beginning of the file.

Method Detail

create

public static Tailer create(File file,
                            TailerListener listener,
                            long delay,
                            boolean end)

Creates and starts a Tailer for the given file.

Parameters:

file - the file to follow.

listener - the TailerListener to use.

delay - the delay between checks of the file for new content in milliseconds.

end - Set to true to tail from the end of the file, false to tail from the beginning of the file.

Returns:

The new tailer

create

public static Tailer create(File file,
                            TailerListener listener,
                            long delay)

Creates and starts a Tailer for the given file, starting at the beginning of the file

Parameters:

file - the file to follow.

listener - the TailerListener to use.

delay - the delay between checks of the file for new content in milliseconds.

Returns:

The new tailer

create

public static Tailer create(File file,
                            TailerListener listener)

Creates and starts a Tailer for the given file, starting at the beginning of the file with the default delay of 1.0s

Parameters:

file - the file to follow.

listener - the TailerListener to use.

Returns:

The new tailer

getFile

public File getFile()

Return the file.

Returns:

the file

getDelay

public long getDelay()

Return the delay.

Returns:

the delay

run

public void run()

Follows changes in the file, calling the TailerListener's handle method for each new line.

Specified by:

run in interface Runnable

stop

public void stop()

Allows the tailer to complete its current loop and return.