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Typesafe Config

The TypesafeConfigAction will search in a variety of places for configuration using standard fallback behavior for Typesafe Config, which gives a richer experience to end users.

Config config = systemProperties        // Look for a property from system properties first...
        .withFallback(file)          // if we don't find it, then look in an explicitly defined file...
        .withFallback(testResources) // if not, then if logback-test.conf exists, look for it there...
        .withFallback(resources)     // then look in logback.conf...
        .withFallback(reference)     // and then finally in logback-reference.conf.
        .resolve();                  // Tell config that we want to use ${?ENV_VAR} type stuff.

The configuration is then placed in the LoggerContext which is available to all of Logback.

lc.putObject(ConfigConstants.TYPESAFE_CONFIG_CTX_KEY, config);

And then all properties are made available to Logback, either at the local scope or at the context scope.

Properties must be strings, but you can also provide Maps and Lists to the Logback Context, through context.getObject.

Log Levels and Properties through Typesafe Config

Configuration of properties and setting log levels is done through Typesafe Config, using TypesafeConfigAction

Here's the logback.conf from the example application. It's in Human-Optimized Config Object Notation or HOCON.

# Set logger levels here.
levels = {
    # Override the default root log level with ROOT_LOG_LEVEL environment variable, if defined...
    ROOT = ${?ROOT_LOG_LEVEL}

    # You can set a logger with a simple package name.
    example = DEBUG

    # You can also do nested overrides here.
    deeply.nested {
        package = TRACE
    }
}

# Overrides the properties from logback-reference.conf
local {

    logback.environment=production

    censor {
        regex = """hunter2""" // http://bash.org/?244321
        replacementText = "*******"
        json.keys += "password" // adding password key will remove the key/value pair entirely
    }

    # Overwrite text file on every run.
    textfile {
        append = false
    }

    # Override the color code in console for info statements
    highlight {
        info = "black"
    }
}

# You can also include settings from other places
include "myothersettings"

For tests, there's a logback-test.conf that will override (rather than completely replace) any settings that you have in logback.conf:

include "logback-reference"

levels {
  example = TRACE
}

local {
  logback.environment=test

  textfile {
    location = "log/test/application-test.log"
    append = false
  }

  jsonfile {
    location = "log/test/application-test.json"
    prettyprint = true
  }
}

There is also a logback-reference.conf file that handles the default configuration for the appenders, and those settings can be overridden. They are written out individually in the encoder configuration so I won't go over it here.

Note that appender logic is not available here -- it's all defined through the structured-config in logback.xml.

Using Typesafe Config is not a requirement -- the point here is to show that there are more options to configuring Logback than using a straight XML file.

See Application Logging in Java: Adding Configuration for more details.