Package org.apache.commons.io.input
Class Tailer
java.lang.Object
org.apache.commons.io.input.Tailer
- All Implemented Interfaces:
AutoCloseable
,Runnable
Simple implementation of the UNIX "tail -f" functionality.
To build an instance, use 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 AddTailer.Tailable
andTailer.RandomAccessResourceBridge
interfaces to tail of files accessed using alternative libraries such as jCIFS or Apache Commons VFS. - See Also:
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
Builds a newTailer
.private static final class
Bridges random access to aRandomAccessFile
.static interface
Bridges access to a resource for random access, normally a file.static interface
A tailable resource like a file.private static final class
A tailable for a filePath
. -
Field Summary
FieldsModifier and TypeFieldDescriptionprivate final Charset
The character set that will be used to read the file.private static final Charset
private static final int
private final Duration
The amount of time to wait for the file to be updated.private final byte[]
Buffer on top of RandomAccessResourceBridge.private final TailerListener
The listener to notify of events when tailing.private static final String
private final boolean
Whether to close and reopen the file whilst waiting for more input.private boolean
The tailer will run as long as this value is true.private final Tailer.Tailable
The file which will be tailed.private final boolean
Whether to tail from the end or start of file -
Constructor Summary
ConstructorsModifierConstructorDescriptionTailer
(File file, Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize) Deprecated.Tailer
(File file, TailerListener listener) Deprecated.Tailer
(File file, TailerListener listener, long delayMillis) Deprecated.Tailer
(File file, TailerListener listener, long delayMillis, boolean end) Deprecated.Tailer
(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated.Tailer
(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.Tailer
(File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated.private
Tailer
(Tailer.Tailable tailable, Charset charset, TailerListener listener, Duration delayDuration, boolean end, boolean reOpen, int bufferSize) Creates a Tailer for the given file, with a specified buffer size. -
Method Summary
Modifier and TypeMethodDescriptionstatic Tailer.Builder
builder()
Constructs a newTailer.Builder
.void
close()
Requests the tailer to complete its current loop and return.static Tailer
create
(File file, Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.static Tailer
create
(File file, TailerListener listener) Deprecated.static Tailer
create
(File file, TailerListener listener, long delayMillis) Deprecated.static Tailer
create
(File file, TailerListener listener, long delayMillis, boolean end) Deprecated.static Tailer
create
(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated.static Tailer
create
(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.static Tailer
create
(File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated.long
getDelay()
Deprecated.UsegetDelayDuration()
.Gets the delay Duration.getFile()
Gets the file.protected boolean
getRun()
Gets whether to keep on running.Gets the Tailable.private long
Reads new lines.void
run()
Follows changes in the file, callingTailerListener.handle(String)
with each new line.void
stop()
Deprecated.Useclose()
.
-
Field Details
-
DEFAULT_DELAY_MILLIS
private static final int DEFAULT_DELAY_MILLIS- See Also:
-
RAF_READ_ONLY_MODE
- See Also:
-
DEFAULT_CHARSET
-
inbuf
private final byte[] inbufBuffer on top of RandomAccessResourceBridge. -
tailable
The file which will be tailed. -
charset
The character set that will be used to read the file. -
delayDuration
The amount of time to wait for the file to be updated. -
tailAtEnd
private final boolean tailAtEndWhether to tail from the end or start of file -
listener
The listener to notify of events when tailing. -
reOpen
private final boolean reOpenWhether to close and reopen the file whilst waiting for more input. -
run
private volatile boolean runThe tailer will run as long as this value is true.
-
-
Constructor Details
-
Tailer
@Deprecated public Tailer(File file, Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize) Deprecated.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 filelistener
- 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 chunksbufSize
- Buffer size
-
Tailer
Deprecated.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.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.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(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated.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(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.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 chunksbufferSize
- Buffer size
-
Tailer
@Deprecated public Tailer(File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated.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
-
Tailer
private Tailer(Tailer.Tailable tailable, Charset charset, TailerListener listener, Duration delayDuration, boolean end, boolean reOpen, int bufferSize) Creates a Tailer for the given file, with a specified buffer size.- Parameters:
tailable
- the file to follow.charset
- the Charset to be used for reading the filelistener
- the TailerListener to use.delayDuration
- 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 chunksbufferSize
- Buffer size
-
-
Method Details
-
builder
Constructs a newTailer.Builder
.- Returns:
- Creates a new
Tailer.Builder
. - Since:
- 2.12.0
-
create
@Deprecated public static Tailer create(File file, Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.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.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.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(File file, TailerListener listener, long delayMillis, boolean end) Deprecated.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(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen) Deprecated.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(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufferSize) Deprecated.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(File file, TailerListener listener, long delayMillis, boolean end, int bufferSize) Deprecated.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 interfaceAutoCloseable
-
getDelay
Deprecated.UsegetDelayDuration()
.Gets the delay in milliseconds.- Returns:
- the delay in milliseconds.
-
getDelayDuration
Gets the delay Duration.- Returns:
- the delay Duration.
- Since:
- 2.12.0
-
getFile
Gets the file.- Returns:
- the file
- Throws:
IllegalStateException
- if constructed using a user providedTailer.Tailable
implementation
-
getRun
protected boolean getRun()Gets whether to keep on running.- Returns:
- whether to keep on running.
- Since:
- 2.5
-
getTailable
Gets the Tailable.- Returns:
- the Tailable
- Since:
- 2.12.0
-
readLines
Reads new lines.- Parameters:
reader
- The file to read- Returns:
- The new position after the lines have been read
- Throws:
IOException
- if an I/O error occurs.
-
run
public void run()Follows changes in the file, callingTailerListener.handle(String)
with each new line. -
stop
Deprecated.Useclose()
.Requests the tailer to complete its current loop and return.
-
builder()
,Tailer.Builder
, andTailer.Builder.get()
.