Log4j 2 EnvironmentConfigurationFactory

What is this?

This project provides a ConfigurationFactory subclass for configuring Log4j 2 from system properties and environment variables.

Getting started

You can use EnvironmentConfigurationFactory in your projects by including it as a Maven dependency:

<dependency>
  <groupId>net.logicsquad</groupId>
  <artifactId>log4j2-envconfig</artifactId>
  <version>1.0</version>
</dependency>

Add src/main/resources/log4j2.component.properties containing the following property:

log4j.configurationFactory=net.logicsquad.log4j.config.EnvironmentConfigurationFactory

You can now use system properties or environment variables to configure Log4j 2.

System properties

EnvironmentConfigurationFactory searches system properties for keys beginning with app.logging.. These keys then have the app.logging. prefix removed, and are used with their values to configure Log4j 2. For example: app.logging.status=ERROR is converted to status=ERROR, and this property is used in configuration.

EnvironmentConfigurationFactory will also parse a custom "quick syntax" for declaring Loggers. Log4j 2 configuration takes two properties to configure each Logger, compared to Log4j 1's single property. You can use properties of the form:

app.logging.quick.<Logger name>=<level>

For example:

app.logging.quick.net.logicsquad.foo.bar.SomeClass=WARN

is equivalent to:

app.logging.logger.log1.name=net.logicsquad.foo.bar.SomeClass
app.logging.logger.log1.level=WARN

Note that this syntax is available only via system properties, and won't be parsed via environment variables.

Environment variables

EnvironmentConfigurationFactory searches environment variables for keys beginning with APP_LOGGING_. These keys then have the APP_LOGGING_ prefix removed, and the remaining string lowercased (except where a Log4j 2 keyword is case-sensitive, e.g. customLevel—these are handled as special cases), and are used with their values to configure Log4j 2. For example: APP_LOGGING_ROOTLOGGER_LEVEL=DEBUG is converted to rootLogger.level=DEBUG, and this property is used in configuration.

Contributing

By all means, open issue tickets and pull requests if you have something to contribute.

References

EnvironmentConfigurationFactory was inspired by Romain Manni-Bucau's article "Log4j2: how to configure your logging with environment variables".