Re: How should I provide access to my logger?

"Mike Schilling" <>
Mon, 30 Mar 2009 01:55:10 -0700
Fencer wrote:

Hello, I've been tasked with implementing a logging feature to a
program consisting of maybe 100 classes. I've implemented the GUI
side of this feature (a window where this information will be
displayed, it can go to a file as well).
Now I'm wondering what the best way is to make my logger available
the classes that needs to use it. I could add a parameter to the
constructors, I suppose, but that doesn't feel right to me. The
idea is to replace many System.out/err.println() calls that are
scattered throughout the code with this logging class.
The users of the logging class don't know or care if the logger just
writes to a file, and/or displays it in a special window or if it's
even turned of.
Maybe I could use a singleton as my logger? So when a class A wants
log something it obtains a logger object and uses it. I want the
to be able to change the behavior of the logging during runtime, and
think I can do that with this approach. But since I'm not a seasoned
Java programmer I ask here for advice.
Also, this program is single-threaded, at least, I'm not creating
new threads myself explicitly. I'm using Java 1.6.0_13.

Look into java.util.logging. You can use its Loggers to divide the
logged messages in two dimensions:

1. Type of message, which you accomplish by logging messages to
different instances of Logger.
2. Priority of message, which you accomplish by logging them at
different Levels.

The GUI you've written will be part of a Handler, that is, a class
that accepts a logged message and processes it in some fashion. As
you say, the client code just logs messages, and has no idea how (or
whether) they're displayed, saved to disk, etc. And that can be
changed that by editing a configuration file that determines which
Handlers are created.

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