LittleLogger - A very simple Java/Scala logging utility

A lot of times when I’m writing small test applications I want/need a logger, but I don’t want to deal with the complexities of traditional Java/Scala logging utilities. This morning I finally took a little time to write a very simple logger that I can use in these small applications and test projects. I call it LittleLogger, and I’ll share the Scala source code here today.

LittleLogger.scala

There is only one class in my logger, and it’s named LittleLogger.scala. Without the comments, the source code looks like this:

package com.valleyprogramming.littlelogger

import java.io._
import java.util.Calendar
import java.text.SimpleDateFormat

class LittleLogger(identifier: String) {

    val timeFormatter = new SimpleDateFormat("hh:mm:ss:SSS")

    def init(filename: String) { 
        LittleLogger.filename = filename
        val file = new File(filename)
        file.createNewFile
    }

    def log(msg: String) {
        if (LittleLogger.filename == null) {
            System.err.println("LittleLogger: `filename` was null, not going to write anything")
            return
        }
        val bw = new BufferedWriter(new FileWriter(new File(LittleLogger.filename), true))
        bw.write(s"$identifier | $getTime | $msg\n")
        bw.close
    }
    
    private def getTime = timeFormatter.format(Calendar.getInstance.getTime)

}

object LittleLogger {
    
    private var filename: String = _
    
    def apply(identifier: String): LittleLogger = new LittleLogger(identifier)

}

As you can see, I intentionally do some things wrong here, primarily the use of null values. That’s a big no-no in production Scala applications, but because I want to enforce the notion that this logger shouldn’t be used in production applications I’m leaving those null values in there.

Usage

LittleLogger is easy to use. The following “driver” class shows how to initialize and use it in multiple Scala classes:

object MainDriver extends App {

    val logger = LittleLogger("MainDriver")
    logger.init("/Users/Al/Projects/Scala/LittleLogger/log.out")
    
    new Foo
    new Bar

}

class Foo {    
    val logger = LittleLogger(this.getClass.getName)
    logger.log("made it to A")
    logger.log("made it to B")
}

class Bar {    
    val logger = LittleLogger("Bar")
    logger.log("made it to A")
    logger.log("made it to B")
}

The output from this driver/test application looks like this:

com.valleyprogramming.littlelogger.Foo | 10:27:47:032 | made it to A
com.valleyprogramming.littlelogger.Foo | 10:27:47:033 | made it to B
Bar | 10:27:47:060 | made it to A
Bar | 10:27:47:061 | made it to B

You’ll want a lot more functionality than this for production projects, but for little one-off projects, this is all I need.

More information and project source code

That’s really all there is to the LittleLogger. I was driven to create this little project by two feelings:

1. I got tired of trying to find Java/Scala System.out.println output on Mac OS X systems.
2. I don’t like the complexity of traditional logging utilities for simple/little projects.

You can find more information and the complete project source code on Github at this URL: github.com/alvinj/LittleLogger

One final note: Please don’t use this code in production applications, it’s really not intended for that sort of thing.

Reporting live from Boulder, Colorado with more Scala source code, this is Alvin Alexander.