FileHandler

Class Overview

A FileHandler writes logging records into a specified file or a rotating set of files.

When a set of files is used and a given amount of data has been written to one file, then this file is closed and another file is opened. The name of these files are generated by given name pattern, see below for details. When the files have all been filled the Handler returns to the first and goes through the set again.

By default, the I/O buffering mechanism is enabled, but when each log record is complete, it is flushed out.

XMLFormatter is the default formatter for FileHandler.

FileHandler reads the following LogManager properties for initialization; if a property is not defined or has an invalid value, a default value is used.

• java.util.logging.FileHandler.append specifies whether this FileHandler should append onto existing files, defaults to false.
• java.util.logging.FileHandler.count specifies how many output files to rotate, defaults to 1.
• java.util.logging.FileHandler.filter specifies the Filter class name, defaults to no Filter.
• java.util.logging.FileHandler.formatter specifies the Formatter class, defaults to java.util.logging.XMLFormatter.
• java.util.logging.FileHandler.encoding specifies the character set encoding name, defaults to the default platform encoding.
• java.util.logging.FileHandler.level specifies the level for this Handler, defaults to Level.ALL.
• java.util.logging.FileHandler.limit specifies the maximum number of bytes to write to any one file, defaults to zero, which means no limit.
• java.util.logging.FileHandler.pattern specifies name pattern for the output files. See below for details. Defaults to "%h/java%u.log".

Name pattern is a string that may include some special substrings, which will be replaced to generate output files:

• "/" represents the local pathname separator
• "%g" represents the generation number to distinguish rotated logs
• "%h" represents the home directory of the current user, which is specified by "user.home" system property
• "%t" represents the system's temporary directory
• "%u" represents a unique number to resolve conflicts
• "%%" represents the percent sign character '%'

Normally, the generation numbers are not larger than the given file count and follow the sequence 0, 1, 2.... If the file count is larger than one, but the generation field("%g") has not been specified in the pattern, then the generation number after a dot will be added to the end of the file name.

The "%u" unique field is used to avoid conflicts and is set to 0 at first. If one FileHandler tries to open the filename which is currently in use by another process, it will repeatedly increment the unique number field and try again. If the "%u" component has not been included in the file name pattern and some contention on a file does occur, then a unique numerical value will be added to the end of the filename in question immediately to the right of a dot. The generation of unique IDs for avoiding conflicts is only guaranteed to work reliably when using a local disk file system.

Summary

[Expand] Inherited Methods
From class java.util.logging.StreamHandler void close() Closes this handler. void flush() Flushes any buffered output. boolean isLoggable(LogRecord record) Determines whether the supplied log record needs to be logged. synchronized void publish(LogRecord record) Accepts a logging request. void setEncoding(String encoding) Sets the character encoding used by this handler. void setOutputStream(OutputStream os) Sets the output stream this handler writes to.
From class java.util.logging.Handler abstract void close() Closes this handler. abstract void flush() Flushes any buffered output. String getEncoding() Gets the character encoding used by this handler, null for default encoding. ErrorManager getErrorManager() Gets the error manager used by this handler to report errors during logging. Filter getFilter() Gets the filter used by this handler. Formatter getFormatter() Gets the formatter used by this handler to format the logging messages. Level getLevel() Gets the logging level of this handler, records with levels lower than this value will be dropped. boolean isLoggable(LogRecord record) Determines whether the supplied log record needs to be logged. abstract void publish(LogRecord record) Accepts a logging request and sends it to the the target. void reportError(String msg, Exception ex, int code) Reports an error to the error manager associated with this handler, ErrorManager is used for that purpose. void setEncoding(String encoding) Sets the character encoding used by this handler, null indicates a default encoding. void setErrorManager(ErrorManager em) Sets the error manager for this handler. void setFilter(Filter newFilter) Sets the filter to be used by this handler. void setFormatter(Formatter newFormatter) Sets the formatter to be used by this handler. void setLevel(Level newLevel) Sets the logging level of the messages logged by this handler, levels lower than this value will be dropped.
From class java.lang.Object Object clone() Creates and returns a copy of this Object. boolean equals(Object o) 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() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object. final void wait(long millis, 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 millis) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.