Package org.apache.commons.io.input

Class Tailer

  • All Implemented Interfaces:
    java.lang.Runnable
    public class Tailer
extends java.lang.Object
implements java.lang.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:

    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 Using 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 Using 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. Stopping a Tailer

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

          tailer.stop();

    4. Interrupting a Tailer

    You can interrupt the thread a tailer is running on by calling Thread.interrupt(). 

          thread.interrupt();

    If you interrupt a tailer, the tailer listener is called with the InterruptedException.

    The file is read using the default charset; this can be overridden if necessary.

    Since:
    2.0, 2.5 Updated behavior and documentation for Thread.interrupt()
    See Also:
    TailerListener, TailerListenerAdapter

    • Constructor Summary

      Constructors 
      Constructor Description
      Tailer​(java.io.File file, java.nio.charset.Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize)
      Creates a Tailer for the given file, with a specified buffer size.
      Tailer​(java.io.File file, TailerListener listener)
      Creates a Tailer for the given file, starting from the beginning, with the default delay of 1.0s.
      Tailer​(java.io.File file, TailerListener listener, long delayMillis)
      Creates a Tailer for the given file, starting from the beginning.
      Tailer​(java.io.File file, TailerListener listener, long delayMillis, boolean end)
      Creates a Tailer for the given file, with a delay other than the default 1.0s.
      Tailer​(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen)
      Creates a Tailer for the given file, with a delay other than the default 1.0s.
      Tailer​(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize)
      Creates a Tailer for the given file, with a specified buffer size.
      Tailer​(java.io.File file, TailerListener listener, long delayMillis, boolean end, int bufSize)
      Creates a Tailer for the given file, with a specified buffer size.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static Tailer create​(java.io.File file, java.nio.charset.Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize)
      Creates and starts a Tailer for the given file.
      static Tailer create​(java.io.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​(java.io.File file, TailerListener listener, long delayMillis)
      Creates and starts a Tailer for the given file, starting at the beginning of the file
      static Tailer create​(java.io.File file, TailerListener listener, long delayMillis, boolean end)
      Creates and starts a Tailer for the given file with default buffer size.
      static Tailer create​(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen)
      Creates and starts a Tailer for the given file with default buffer size.
      static Tailer create​(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize)
      Creates and starts a Tailer for the given file.
      static Tailer create​(java.io.File file, TailerListener listener, long delayMillis, boolean end, int bufSize)
      Creates and starts a Tailer for the given file.
      long getDelay()
      Return the delay in milliseconds.
      java.io.File getFile()
      Return the file.
      protected boolean getRun()
      Gets whether to keep on running.
      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​(java.io.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​(java.io.File file,
              TailerListener listener,
              long delayMillis)
        Creates a Tailer for the given file, starting from the beginning.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - the delay between checks of the file for new content in milliseconds.

      • Tailer

        public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              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.
        delayMillis - 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.

      • Tailer

        public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen)
        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.
        delayMillis - 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.
        reOpen - if true, close and reopen the file between reading chunks

      • Tailer

        public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              int bufSize)
        Creates a Tailer for the given file, with a specified buffer size.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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.
        bufSize - Buffer size

      • Tailer

        public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen,
              int bufSize)
        Creates a Tailer for the given file, with a specified buffer size.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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.
        reOpen - if true, close and reopen the file between reading chunks
        bufSize - Buffer size

      • Tailer

        public Tailer​(java.io.File file,
              java.nio.charset.Charset charset,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen,
              int bufSize)
        Creates a Tailer for the given file, with a specified buffer size.
        Parameters:
        file - the file to follow.
        charset - the Charset to be used for reading the file
        listener - the TailerListener to use.
        delayMillis - 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.
        reOpen - if true, close and reopen the file between reading chunks
        bufSize - Buffer size

    • Method Detail

      • create

        public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            int bufSize)
        Creates and starts a Tailer for the given file.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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.
        bufSize - buffer size.
        Returns:
        The new tailer

      • create

        public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen,
                            int bufSize)
        Creates and starts a Tailer for the given file.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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.
        reOpen - whether to close/reopen the file between chunks
        bufSize - buffer size.
        Returns:
        The new tailer

      • create

        public static Tailer create​(java.io.File file,
                            java.nio.charset.Charset charset,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen,
                            int bufSize)
        Creates and starts a Tailer for the given file.
        Parameters:
        file - the file to follow.
        charset - the character set to use for reading the file
        listener - the TailerListener to use.
        delayMillis - 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.
        reOpen - whether to close/reopen the file between chunks
        bufSize - buffer size.
        Returns:
        The new tailer

      • create

        public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end)
        Creates and starts a Tailer for the given file with default buffer size.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen)
        Creates and starts a Tailer for the given file with default buffer size.
        Parameters:
        file - the file to follow.
        listener - the TailerListener to use.
        delayMillis - 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.
        reOpen - whether to close/reopen the file between chunks
        Returns:
        The new tailer

      • create

        public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis)
        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.
        delayMillis - the delay between checks of the file for new content in milliseconds.
        Returns:
        The new tailer

      • create

        public static Tailer create​(java.io.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 java.io.File getFile()
        Return the file.
        Returns:
        the file

      • getRun

        protected boolean getRun()
        Gets whether to keep on running.
        Returns:
        whether to keep on running.
        Since:
        2.5

      • getDelay

        public long getDelay()
        Return the delay in milliseconds.
        Returns:
        the delay in milliseconds.

      • run

        public void run()
        Follows changes in the file, calling the TailerListener's handle method for each new line.
        Specified by:
        run in interface java.lang.Runnable

      • stop

        public void stop()
        Allows the tailer to complete its current loop and return.