Friday, January 21, 2011

Clickable logging messages

Probably everyone is using logging. The dirty way is to use System.out/err, a better solution is to use the JDK logging or some logging library, such as log4j (or a facade, e.g., slf4j) -- and of course Log4E to generate the logger declaration and other logging code . For rich clients and small tools, I usually use the JDK logging, as I do not have to add another library and the logging is only used for development purposes. For web (or other server) applications, in which logging is an important monitoring tool, other log libraries may be a better choice. Anyway, when using the JDK logging facilities, the log message is written to the Eclipse console view by default. A simple log message usually looks like that:
Jan 14, 2011 4:36:54 PM my.project.MyClass bar
INFO: Demo
This is ok, however I usually do not need the date and time. Also, IMHO two lines for a single message waste too much of my console view space. I have written a small formatter, which produces the following output (scroll to the right to see the whole ouput):
I Demo                     at
That is, the date and time is omitted (as this usually is not needed for development purposes), and instead of printing the full logging level, abbreviations are used (I - info,W - Warning, S - Severe and so on). In case of shorter messages, the location information is printed on the same line with some tabs between message and location for better readability. The best thing about that format is, that the Eclipse console recognizes the location and makes it available as a link, which directly opens the location in the source code where the log message was produced. If you configure the console preferences to use gray for standard error text (as which the log message is interpreted due to the location format), you will something like that:
W Test Warning             at my.project.LoggingTest.main(
I Test Info                at my.project.LoggingTest.main(
Actually, I'm using this formatter for quite some years now. Today I have created an project called delofo (short for Developer Logging Formatter) with this formatter. I've chosen because the formatter is optimized for the Eclipse console view, although the project does not provide a plugin and can be used w/o Eclipse. In the project wiki, you will find an installation guide, explaining how to globally install the formatter. By installing the formatter globally, you do not have to modify your projects in anyway.