org.apache.commons.io.input

Class Tailer

java.lang.Object

org.apache.commons.io.input.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:

• Using a Tailer.Builder
• Using an Executor
• Using a Thread

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Tailer.Builder Builds a Tailer with default values.
static interface	Tailer.RandomAccessResourceBridge Bridges access to a resource for random access, normally a file.
static interface	Tailer.Tailable A tailable resource like a file.

Constructor Summary

Constructors

Constructor and Description
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().
Tailer(java.io.File file, TailerListener listener) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
Tailer(java.io.File file, TailerListener listener, long delayMillis) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
Tailer(java.io.File file, TailerListener listener, long delayMillis, boolean end) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
Tailer(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
Tailer(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
Tailer(java.io.File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().

Method Summary

Modifier and Type	Method and Description
static Tailer.Builder	builder() Constructs a new Tailer.Builder.
void	close() Requests the tailer to complete its current loop and return.
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().
static Tailer	create(java.io.File file, TailerListener listener) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
static Tailer	create(java.io.File file, TailerListener listener, long delayMillis) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
static Tailer	create(java.io.File file, TailerListener listener, long delayMillis, boolean end) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
static Tailer	create(java.io.File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
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().
static Tailer	create(java.io.File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated. Use builder(), Tailer.Builder, and Tailer.Builder.get().
long	getDelay() Deprecated. Use getDelayDuration().
java.time.Duration	getDelayDuration() Gets the delay Duration.
java.io.File	getFile() Gets the file.
Tailer.Tailable	getTailable() Gets the Tailable.
void	run() Follows changes in the file, calling TailerListener.handle(String) with each new line.
void	stop() Deprecated. Use close().

Methods inherited from class java.lang.Object

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

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

builder

public static Tailer.Builder builder()

Constructs a new Tailer.Builder.

Returns:

Creates a new Tailer.Builder.

Since:

2.12.0

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.