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Getting Started with Configs

MittenLib's Config Annotation Processor transforms simple Java interfaces or classes into high-performance, immutable configuration objects with built-in validation and Guice integration.

New to MittenLib?

Follow the Config System Tutorial for a step-by-step guide on building your first configuration.

Core Concept​

Instead of writing thousands of lines of boilerplate for parsing and validation, you define your configuration's structure (often called a DTO).

@Config
@Source("config.yml")
public interface MyConfig {
    String serverName();
    
    @Min(1)
    default int maxPlayers() {
        return 20;
    }
}

The annotation processor then generates:

  1. Implementation: An immutable class (MyConfigImpl) with getters, equals, hashCode, and toString.
  2. Logic: Dedicated Deserializer, Serializer, and Validator classes.
  3. Metadata: A public static final Configuration<MyConfig> CONFIG constant (if @Source is present).

How Generation Works​

MittenLib supports two ways of defining configuration structures.

Defining your config as an interface is the cleanest approach.

  • Generated Name: [InterfaceName]Impl (e.g., MyConfig -> MyConfigImpl).
  • Defaults: Use standard Java default methods.
  • Public API: Your application interacts with the interface directly.

2. Classes (DTO Pattern)​

You can also use classes, which is useful if you are porting existing code.

  • Naming Convention: If the class name ends in DTO, the generated class drops the suffix (e.g., MyConfigDTO -> MyConfig).
  • Otherwise: It appends Impl (e.g., MyConfig -> MyConfigImpl).

What is Generated?​

For every @Config type, MittenLib generates several companion classes in the same package:

Generated ClassPurpose
...ImplThe concrete, immutable implementation of your config structure.
...DeserializerHandles converting raw data (via DataTree) into your config objects.
...SerializerHandles converting your config objects back into DataTree format.
...ValidatorEnsures all @Min, @NotBlank, etc., constraints are met.

Integrating with Guice​

The easiest way to use your configs is via the generated ConfigLoaderModule.

public class MyPluginModule extends AbstractModule {
    @Override
    protected void configure() {
        // Registers all your @Config types automatically
        install(new ConfigLoaderModule());
    }
}

Once registered, you can inject a ConfigProvider<T> to access your configuration with support for hot-reloading.

@Inject
public MyService(ConfigProvider<MyConfig> config) {
    this.config = config;
}

Next Steps​

Explore the detailed reference guides to master the configuration system: