Any ideas creating app to read log file when updated?

Question

Afternoon all,
I have been asked to write a java app which will read the contents of the server log file every time the log file is updated by the server. The app will be deployed onto WebSphere Application Server.
Can anyone point me in the right direction as I have never written anything like this before and I don't know where to start. Any help will be much appreciated.
Thanks in advance,
A.

Answer 1

alex@work wrote:
I agree with most of what you've said but unfortunately I don't have a say in what the company wants. However, I am interested in the appender idea, perhaps they may go for that if I suggest it.I'd say it'll take you a day to read up about Log4J and how to write basic appenders, and another day to write your own appender for this problem. Compare that to the effort of writing something to poll a log file, re-read it constantly and update another file, operations which will get slower and slower as they go along. That's a fair amount more code than a single appender would be. There's how to sell it to your company.
Can you give me a brief overview in how it works?Log4J uses objects called appenders, which take logging info - generated by your container - and do something with it. It ships with some appenders already in it, for writing to stdout, files, sockets and databases. You can also write your own appenders that do something more than these standard ones do. You write logging code in your application - in this case, your container already does this so you don't have to - and the configuration of Log4J decides what happens to these logging messages. That's what you're interested in. You could write an appender - a simple class - that takes raw logging messages in, and writes them out to file in whatever format you want
Come to think of it, depending on how complex the required XML is, you may even be able to do this without writing any code at all. You can write formatting patterns in the Log4J config that existing file appenders will use to write your XML files
A bit of an abstract explanation, I guess. Your best bet is to first ascertain that Log4J is indeed in use, and then read the documentation, which is surprisingly good for an Apache project :-)
[http://logging.apache.org/log4j/1.2/index.html]