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Log handlers


Log handlers write log record objects to output devices like log files, sockets, and notification mechanisms.

Loggers can have zero or more attached handlers. All objects that are logged to the logger are passed to the attached handlers, if handlers are supplied.

Configure handlers with a level. The handler compares the level specified in the logged object to the level specified for the handler. If the level of the logged object is less severe than the level set in the handler, the object is ignored by the handler. The default level for handlers is ALL.

Handlers can have a filter. If a filter is supplied, the filter is invoked for each incoming object to tell the handler whether or not to ignore it.

Handlers can have a formatter. If a formatter is supplied, the formatter controls how the logged objects are formatted. For example, the formatter can decide to first include the time stamp, followed by a string representation of the level, followed by the message that is included in the logged object. The handler writes this formatted representation to the output device. Read Example: Creating custom formatters with java.util.logging for information on using a custom formatter in the applications.

Both loggers and handlers can have levels and filters, and a logged object must pass all of these elements to be output. For example, we can set the logger level to FINE, but if the handler level is set at WARNING, only WARNING level messages are displayed in the output for that handler. Conversely, if wer log handler is set to output all messages (level=All), but the logger level is set to WARNING, the logger never sends messages lower than WARNING to the log handler.

WAS uses the following set of log handlers that are available to all loggers:

For instructions on how to configure these log handlers, see Set Java logging .



Related concepts


Loggers
Log filters
Log formatters

 

Related tasks


Set Java logging

 

Related


Log levels