FileHandler

public class FileHandler extends StreamHandler

Simple file logging Handler.

The FileHandler can either write to a specified file, or it can write to a rotating set of files.

For a rotating set of files, as each file reaches a given size limit, it is closed, rotated out, and a new file opened. Successively older files are named by adding "0", "1", "2", etc. into the base filename.

By default buffering is enabled in the IO libraries but each log record is flushed out when it is complete.

By default the XMLFormatter class is used for formatting.

Configuration: By default each FileHandler is initialized using the following LogManager configuration properties. If properties are not defined (or have invalid values) then the specified default values are used.

java.util.logging.FileHandler.level specifies the default level for the Handler (defaults to Level.ALL).
java.util.logging.FileHandler.filter specifies the name of a Filter class to use (defaults to no Filter).
java.util.logging.FileHandler.formatter specifies the name of a Formatter class to use (defaults to java.util.logging.XMLFormatter)
java.util.logging.FileHandler.encoding the name of the character set encoding to use (defaults to the default platform encoding).
java.util.logging.FileHandler.limit specifies an approximate maximum amount to write (in bytes) to any one file. If this is zero, then there is no limit. (Defaults to no limit).
java.util.logging.FileHandler.count specifies how many output files to cycle through (defaults to 1).
java.util.logging.FileHandler.pattern specifies a pattern for generating the output file name. See below for details. (Defaults to "%h/java%u.log").
java.util.logging.FileHandler.append specifies whether the FileHandler should append onto any existing files (defaults to false).

A pattern consists of a string that includes the following special components that will be replaced at runtime:

"/" the local pathname separator
"%t" the system temporary directory
"%h" the value of the "user.home" system property
"%g" the generation number to distinguish rotated logs
"%u" a unique number to resolve conflicts
"%%" translates to a single percent sign "%"

If no "%g" field has been specified and the file count is greater than one, then the generation number will be added to the end of the generated filename, after a dot.

Thus for example a pattern of "%t/java%g.log" with a count of 2 would typically cause log files to be written on Solaris to /var/tmp/java0.log and /var/tmp/java1.log whereas on Windows 95 they would be typically written to C:\TEMP\java0.log and C:\TEMP\java1.log

Generation numbers follow the sequence 0, 1, 2, etc.

Normally the "%u" unique field is set to 0. However, if the FileHandler tries to open the filename and finds the file is currently in use by another process it will increment the unique number field and try again. This will be repeated until FileHandler finds a file name that is not currently in use. If there is a conflict and no "%u" field has been specified, it will be added at the end of the filename after a dot. (This will be after any automatically added generation number.)

Thus if three processes were all trying to log to fred%u.%g.txt then they might end up using fred0.0.txt, fred1.0.txt, fred2.0.txt as the first file in their rotating sequences.

Note that the use of unique ids to avoid conflicts is only guaranteed to work reliably when using a local disk file system.

Public Constructor Summary

	FileHandler() Construct a default `FileHandler`.
	FileHandler(String pattern) Initialize a `FileHandler` to write to the given filename.
	FileHandler(String pattern, boolean append) Initialize a `FileHandler` to write to the given filename, with optional append.
	FileHandler(String pattern, int limit, int count) Initialize a `FileHandler` to write to a set of files.
	FileHandler(String pattern, int limit, int count, boolean append) Initialize a `FileHandler` to write to a set of files with optional append.

Public Method Summary

synchronized void	close() Close all the files.
synchronized void	publish(LogRecord record) Format and publish a `LogRecord`.

Inherited Method Summary

From class java.util.logging.StreamHandler

synchronized void	close() Close the current output stream.
synchronized void	flush() Flush any buffered messages.
boolean	isLoggable(LogRecord record) Check if this `Handler` would actually log a given `LogRecord`.
synchronized void	publish(LogRecord record) Format and publish a `LogRecord`.
synchronized void	setEncoding(String encoding) Set (or change) the character encoding used by this `Handler`.
synchronized void	setOutputStream(OutputStream out) Change the output stream.

From class java.util.logging.Handler

abstract void	close() Close the `Handler` and free all associated resources.
abstract void	flush() Flush any buffered output.
String	getEncoding() Return the character encoding for this `Handler`.
ErrorManager	getErrorManager() Retrieves the ErrorManager for this Handler.
Filter	getFilter() Get the current `Filter` for this `Handler`.
Formatter	getFormatter() Return the `Formatter` for this `Handler`.
Level	getLevel() Get the log level specifying which messages will be logged by this `Handler`.
boolean	isLoggable(LogRecord record) Check if this `Handler` would actually log a given `LogRecord`.
abstract void	publish(LogRecord record) Publish a `LogRecord`.
void	reportError(String msg, Exception ex, int code) Protected convenience method to report an error to this Handler's ErrorManager.
synchronized void	setEncoding(String encoding) Set the character encoding used by this `Handler`.
synchronized void	setErrorManager(ErrorManager em) Define an ErrorManager for this Handler.
synchronized void	setFilter(Filter newFilter) Set a `Filter` to control output on this `Handler`.
synchronized void	setFormatter(Formatter newFormatter) Set a `Formatter`.
synchronized void	setLevel(Level newLevel) Set the log level specifying which message levels will be logged by this `Handler`.

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.

Public Constructors

public FileHandler ()

Construct a default FileHandler. This will be configured entirely from LogManager properties (or their default values).

Throws

IOException	if there are IO problems opening the files.
SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control"))`.
NullPointerException	if pattern property is an empty String.

public FileHandler (String pattern)

Initialize a FileHandler to write to the given filename.

The FileHandler is configured based on LogManager properties (or their default values) except that the given pattern argument is used as the filename pattern, the file limit is set to no limit, and the file count is set to one.

There is no limit on the amount of data that may be written, so use this with care.

Parameters

pattern	the name of the output file

Throws

IOException	if there are IO problems opening the files.
SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control")`.
IllegalArgumentException	if pattern is an empty string

public FileHandler (String pattern, boolean append)

Initialize a FileHandler to write to the given filename, with optional append.

There is no limit on the amount of data that may be written, so use this with care.

Parameters

pattern	the name of the output file
append	specifies append mode

Throws

IOException	if there are IO problems opening the files.
SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control")`.
IllegalArgumentException	if pattern is an empty string

public FileHandler (String pattern, int limit, int count)

Initialize a FileHandler to write to a set of files. When (approximately) the given limit has been written to one file, another file will be opened. The output will cycle through a set of count files.

The count must be at least 1.

Parameters

pattern	the pattern for naming the output file
limit	the maximum number of bytes to write to any one file
count	the number of files to use

Throws

IOException	if there are IO problems opening the files.
SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control")`.
IllegalArgumentException	if limit < 0, or count < 1.
IllegalArgumentException	if pattern is an empty string

public FileHandler (String pattern, int limit, int count, boolean append)

Initialize a FileHandler to write to a set of files with optional append. When (approximately) the given limit has been written to one file, another file will be opened. The output will cycle through a set of count files.

The count must be at least 1.

Parameters

pattern	the pattern for naming the output file
limit	the maximum number of bytes to write to any one file
count	the number of files to use
append	specifies append mode

Throws

IOException	if there are IO problems opening the files.
SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control")`.
IllegalArgumentException	if limit < 0, or count < 1.
IllegalArgumentException	if pattern is an empty string

Public Methods

public synchronized void close ()

Close all the files.

Throws

SecurityException	if a security manager exists and if the caller does not have `LoggingPermission("control")`.

public synchronized void publish (LogRecord record)

Format and publish a LogRecord.

Parameters

record	description of the log event. A null record is silently ignored and is not published