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From "Bender Heri" <HBen...@Ergonomics.ch>
Subject Enhanced FileAppender
Date Mon, 02 Oct 2006 18:12:26 GMT
Hello all

Since in user list nobody commented my suggestion for an enhancement of the FileAppender I
will repeat it here.

Problem:
A often asked issue in user list is the problem to separate log files dependent on different
criterias, like a client-ID in a server environment, a mandant- or task-ID in scheduler applications,
etc. Although it is possible to achieve this with the existing log4j framework all possible
solutions are quite complex  or have other drawbacks (own repository selector, working with
different classloaders, subclass concrete descendents of FileAppender).

Solution:
The FileAppender is supplied with a property of type FileNameBuilder (Design pattern: visitor).
The user-supplied implementation of this Interface can build a filename based on whatever
criterias (i.e. MDC, global Environment, etc.). The visitor is called each time a Fileappender
wants to append a log message. The FileAppender holds a collection of file writers for each
separate file name delivered by FileNameBuilder.
To avoid the excess of open file handles the FileAppender could watch the logging activity
to one particular file. If the file was not accessed after let's say one hour it could be
closed (this timeout could also be configurable). Special care must be done if the property
"append" of the FileAppender is false. If the file was closed because the above timeout had
elapsed and then reopened later again, the file shouldn't be overridden.
If the config file does not specify a FileNameBuilder a default implementation would be used
which returns always the configured filename. This wouldn't break existing code. The existing
property fileName would remain and hold always the configured filename.

The interface of the FileNameBuilder would be like this:

public String buildFilename( FileAppender aFileAppender );


Any comments on this?


Heri

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