Package org.apache.commons.io.input

Class Tailer

  • All Implemented Interfaces:
    java.lang.AutoCloseable, java.lang.Runnable
    public class Tailer
extends java.lang.Object
implements java.lang.Runnable, java.lang.AutoCloseable
    Simple implementation of the UNIX "tail -f" functionality.

    To build an instance, see Tailer.Builder.

    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 is shown below.

    2.1 Using a Builder

     TailerListener listener = new MyTailerListener();
 Tailer tailer = Tailer.builder()
   .setFile(file)
   .setTailerListener(listener)
   .setDelayDuration(delay)
   .get();

    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()., 2.12.0 Add Tailer.Tailable and Tailer.RandomAccessResourceBridge interfaces to tail of files accessed using alternative libraries such as jCIFS or Apache Commons VFS.
    See Also:
    TailerListener, TailerListenerAdapter

    • Constructor Detail

      • Tailer

        @Deprecated
public Tailer​(java.io.File file,
              java.nio.charset.Charset charset,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen,
              int bufSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

      • Tailer

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              boolean reOpen,
              int bufferSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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
        bufferSize - Buffer size

      • Tailer

        @Deprecated
public Tailer​(java.io.File file,
              TailerListener listener,
              long delayMillis,
              boolean end,
              int bufferSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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.
        bufferSize - Buffer size

    • Method Detail

      • create

        @Deprecated
public static Tailer create​(java.io.File file,
                            java.nio.charset.Charset charset,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen,
                            int bufferSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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.
        bufferSize - buffer size.
        Returns:
        The new tailer.

      • create

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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.

      • create

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            boolean reOpen,
                            int bufferSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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.
        bufferSize - buffer size.
        Returns:
        The new tailer.

      • create

        @Deprecated
public static Tailer create​(java.io.File file,
                            TailerListener listener,
                            long delayMillis,
                            boolean end,
                            int bufferSize)
        Deprecated.
        Use builder(), Tailer.Builder, and Tailer.Builder.get().
        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.
        bufferSize - buffer size.
        Returns:
        The new tailer.

      • close

        public void close()
        Requests the tailer to complete its current loop and return.
        Specified by:
        close in interface java.lang.AutoCloseable

      • getDelay

        @Deprecated
public long getDelay()
        Deprecated.
        Use getDelayDuration().
        Gets the delay in milliseconds.
        Returns:
        the delay in milliseconds.

      • getDelayDuration

        public java.time.Duration getDelayDuration()
        Gets the delay Duration.
        Returns:
        the delay Duration.
        Since:
        2.12.0

      • getFile

        public java.io.File getFile()
        Gets the file.
        Returns:
        the file
        Throws:
        java.lang.IllegalStateException - if constructed using a user provided Tailer.Tailable implementation

      • getTailable

        public Tailer.Tailable getTailable()
        Gets the Tailable.
        Returns:
        the Tailable
        Since:
        2.12.0

      • run

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

      • stop

        @Deprecated
public void stop()
        Deprecated.
        Use close().
        Requests the tailer to complete its current loop and return.