A better way to handle properties config files in Java 8.

loadprop loads in properties by mapping them to a plain old Java object. It uses common conventions to do it cleanly and concisely. It's a small, simple library with no external dependencies.

The main ideas behind loadprop:

• To avoid properties file and class from getting out of sync over time:
  • Require 1-to-1 mapping of properties to class fields.
  • Generate errors if there are extra or missing properties.
  • Class members can be marked as optional using Java 8 Optional class.
• Automatically convert fields:
  • Convert all primitive types and their wrappers transparently.
  • Use standard conversions provided by JDK.
  • Generate errors if conversion fails.
  • Allow 0x prefix for hexidecimal whole number types, but not 0 prefix for octal. Have octal constants ever been used intentionally?
• Report errors consistantly with exceptions, providing as much useful information as possible.

// Config.java
class Config {
    public String bindAddr;
    public Optional<Integer> port;
}

// config.properties
bindAddr = 127.0.0.1
port = 80

// main program
PropertiesLoader propertiesLoader = new PropertiesLoader();
Config config = propertiesLoader.load(Config.class, new FileInputStream("config.properties"));
System.out.println("port = " + config.port.orElse(8080));

• Provide mapping from name.something.whatever style properties to camelCase field names.
• More conversions.
• Configurable class properties to ignore.