Avoid printStackTrace(); use a logger call instead

Question

In my application, I am running my code through PMD.It shows me this message:

• Avoid printStackTrace(); use a logger call instead.

What does that mean?

Answer 1

It means you should use logging framework like logback or log4j and instead of printing exceptions directly:

e.printStackTrace(); 

you should log them using this frameworks' API:

log.error("Ops!", e); 

Logging frameworks give you a lot of flexibility, e.g. you can choose whether you want to log to console or file - or maybe skip some messages if you find them no longer relevant in some environment.

Answer 2

If you call printStackTrace() on an exception the trace is written to System.err and it's hard to route it elsewhere (or filter it). Instead of doing this you are advised using a logging framework (or a wrapper around multiple logging frameworks, like Apache Commons Logging) and log the exception using that framework (e.g. logger.error("some exception message", e)).

Doing that allows you to:

• write the log statement to different locations at once, e.g. the console and a file
• filter the log statements by severity (error, warning, info, debug etc.) and origin (normally package or class based)
• have some influence on the log format without having to change the code
• etc.