Utility class to define system properties from files with support for included files

1. Call PropertyFiles.loadSystemProperties() at the start of your application
2. Define either the system property java.properties.file or java.properties.resource when running the application (i.e. java -Djava.properties.file=prod.properties ...)

The .properties file will be loaded and all its properties will be added as system properties.

If the file defines either java.properties.file or java.properties.resource again, the new file will be included before and its properties overridden by the current file. This way you can centralize common properties in one file included by the other specific configurations.

Your application can retrieve configuration values using System.getProperty or an other similar tool working with standard system properties.

Common properties are used to share configuration values, define frequently used default values and define external configuration.

common.properties delivered with application

# Default database configuration
database.jdbc.url = jdbc:mysql://localhost/app
database.jdbc.user = app_user
database.jdbc.password =

# Configure logging
logger.com.company.application = INFO

# Enable debug in Netty
org.jboss.netty.debug =

Developers can have their own configurations to ease debugging. Developers will run the application with -Djava.properties.resource=dev.properties

dev.properties delivered with application

# Include common properties
java.properties.resource = common.properties

# Overrides some parameters
logger.com.company.application = DEBUG

Production can override some settings to comply with the deployment target

prod.properties delivered with application

# Include common properties
java.properties.resource = common.properties

# Overrides some parameters
database.jdbc.user = app_user_prod

An application deployer can avoid storing sensible information by having its own configuration in a file instead of embedded in the application. Deployer will run the application with -Djava.properties.file=prod_secure.properties

prod_secure.properties only managed by application deployer

# Include common properties
java.properties.resource = prod.properties

# Overrides some parameters
database.jdbc.password = Secur3!P@ssw0rd