CODEWITHSUNDEEP
scalaloggingplayframeworkplayframework-2.0
Kieran Benton
Kieran Benton

Reputation: 8900

Logging syntax for Play Framework 2 in Scala

This is a really silly question, but how can you do convenient formatting of log strings in Play Framework 2 (and in Scala?).

I've googled but its very difficult to find an example, essentially most links are talking about configuring Logback in the first place which I've done fine.

I'm basically trying to find the best stylistic way to do something like:

if(Logger.isDebugEnabled)
    Logger.debug("Modified: Id = '" + real_session_id + "', Modified = " + modified.toString)

Coming from a C# background (and log4net) I'd assume you could do something like:

if(Logger.isDebugEnabled)
    Logger.debug("Modified: Id = '{0}', Modified = {1}", real_session_id, modified.toString)

But I can't see how this would work with the trait the way it is defined. I've also seen vague references to how you might be able to avoid checking Logger.isDebugEnabled by using a lazy evaluative syntax like:

Logger.debug("Modified: Id = ${real_session_id}, Modified = ${modified.toString}")

That uses Scala macros - but again, that doesn't work and I can find very little information about it.

Am I missing something really blatant here?

Upvotes: 7

Views: 3898

Answers (2)

i.am.michiel
i.am.michiel

Reputation: 10404

  1. The framework used for logging is logback. When you type : Logger.debug, the isDebugEnabled is already implicitly checked.

  2. For the syntax of logging, use the Scala string interpolation. 

    Logger.debug(s"Modified: Id = '$real_session_id', Modified = $modified.toString")

Upvotes: 9

Erik Kaplun
Erik Kaplun

Reputation: 38247

Why not just use the standard String interpolation capabilities of the language/stdlib? http://docs.scala-lang.org/overviews/core/string-interpolation.html

I apologise if I've missed something crucial about your question.

As to avoiding the if (Logger.isDebugEnabled) check, if the logging framework is not providing some sort of lazy evaluation scheme for arguments passed into it, I would just first consider defining my own wrappers:

object MyLazyLogger {
  def debug(msg: => Any) =
    if (Logger.isDebugEnabled) Logger.debug(msg)
}

Also, I don't think the way in which you interpolate stuff into the string has anything to do with not evaluating the arguments to debug() if logging is disabled—if debug() declares that it eager-evaluates any arguments passed into it, there's no way that I can see you can change to lazy evaluation at the call site by just using a "special form" of string interpolation. (I'd be happy if anyone proved me wrong here and taught me something new :))

Disclosure: I'm not familiar with Play (yet), so I'm just taking a shot at a general approach here.

Upvotes: 1

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