Package org.apache.commons.io.input
Class Tailer
java.lang.Object
org.apache.commons.io.input.Tailer
- All Implemented Interfaces:
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:
-
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 long
The amount of time to wait for the file to be updated.private final boolean
Whether to tail from the end or start of fileprivate final File
The file which will be tailed.private final byte[]
Buffer on top of RandomAccessFile.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. -
Constructor Summary
ConstructorsConstructorDescriptionTailer
(File file, 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
(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 delayMillis) Creates a Tailer for the given file, starting from the beginning.Tailer
(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
(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
(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
(File file, TailerListener listener, long delayMillis, boolean end, int bufSize) Creates a Tailer for the given file, with a specified buffer size. -
Method Summary
Modifier and TypeMethodDescriptionstatic Tailer
create
(File file, Charset charset, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize) Creates and starts a Tailer for the given file.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 1.0sstatic Tailer
create
(File file, TailerListener listener, long delayMillis) Creates and starts a Tailer for the given file, starting at the beginning of the filestatic Tailer
create
(File file, TailerListener listener, long delayMillis, boolean end) Creates and starts a Tailer for the given file with default buffer size.static Tailer
create
(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
(File file, TailerListener listener, long delayMillis, boolean end, boolean reOpen, int bufSize) Creates and starts a Tailer for the given file.static Tailer
create
(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.getFile()
Return the file.protected boolean
getRun()
Gets whether to keep on running.private long
readLines
(RandomAccessFile reader) Read new lines.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.
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Field Details
-
DEFAULT_DELAY_MILLIS
private static final int DEFAULT_DELAY_MILLIS- See Also:
-
RAF_MODE
- See Also:
-
DEFAULT_CHARSET
-
inbuf
private final byte[] inbufBuffer on top of RandomAccessFile. -
file
The file which will be tailed. -
charset
The character set that will be used to read the file. -
delayMillis
private final long delayMillisThe amount of time to wait for the file to be updated. -
end
private final boolean endWhether 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.
-
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Constructor Details
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Tailer
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
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
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
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
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(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 chunksbufSize
- Buffer size
-
Tailer
public Tailer(File file, 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 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
-
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Method Details
-
create
public static Tailer create(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(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 chunksbufSize
- buffer size.- Returns:
- The new tailer
-
create
public static Tailer create(File file, 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 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
- whether to close/reopen the file between chunksbufSize
- buffer size.- Returns:
- The new tailer
-
create
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(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
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
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
Return the file.- Returns:
- the file
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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.
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run
public void run()Follows changes in the file, calling the TailerListener's handle method for each new line. -
stop
public void stop()Allows the tailer to complete its current loop and return. -
readLines
Read 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.
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