Rhea

Rhea is a type-safe dynamic configuration library for JVM applications. This library uses asynchronous data flows that gives a natural auto-reloading feature in runtime, so it allows to change configuration properties and get the freshest values in your application without the need to restart.

Features

• Open source project under the MIT License
• Extendable with user-defined property types
• Extendable with user-defined configuration sources
• Supports reading configuration from files (.yaml, .properties, .json), Vault, JDBC, MongoDB

Getting Started

Setting up dependency

To get started, add uk.dsxt:rhea-core:<version> as a dependency:

Gradle

dependencies {
  compile group: "uk.dsxt", name:"rhea-core", version: "0.0.1-SNAPSHOT"
}

Maven

<dependencies>
  <dependency>
    <groupId>uk.dsxt</groupId>
    <artifactId>rhea-core</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </dependency>
</dependencies>

Configuration Sources

To read configuration from source other than .properties, add its rhea module as a dependency. For example, to add .json as configuration source:

Gradle

dependencies {
  ...
  compile group: "uk.dsxt", name:"rhea-json", version: "0.0.1-SNAPSHOT"
}

Maven

<dependencies>
    ...
  <dependency>
    <groupId>uk.dsxt</groupId>
    <artifactId>rhea-json</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </dependency>
</dependencies>

Note: If configuration source is not supported, you can add it by implementing ConfigSource interface.

Usage

Java

1. Build a configuration object that holds properties, add configuration sources

   ConfigSource jsonSource =
       new JsonConfigSource(Paths.get("src" + File.separator + "test" + File.separator + "resources"), "jsonSource.json");
       
   ReactiveConfig config = new ReactiveConfig.Builder()
       .addSource("jsonConfig", jsonSource)
       .build();

2. Create reloadable properties

   Reloadable<Boolean> isSomethingOn = config.get("flag", PropertyTypesKt.booleanType);
   Reloadable<Integer> port = config.get("port", PropertyTypesKt.intType);
   
   // access the freshest typed values with get()
   Server server = new Server(port.get(), "host");
   if (isSomethingOn.get()) {
       server.start();
   }

3. Also, you can add some complex logic that will execute every time the property is changed

   port.onChange((Integer newValue) -> {
       // for example, restart server
   });

Kotlin

1. Build a configuration object that holds properties, add configuration sources

   val jsonSource: ConfigSource =
       JsonConfigSource(Paths.get("src" + File.separator + "test" + File.separator + "resources"), "jsonSource.json")
       
   val config: ReactiveConfig = ReactiveConfig.Builder()
       .addSource("jsonConfig", jsonSource)
       .build()

2. Create reloadable properties or declare objects that extend PropertyGroup to define hierarchies of properties

   val isSomethingOn: Realoadable<Boolean> = config["flag", booleanType]
   object server : PropertyGroup() {
       val name by stringType
       val port by intType
   }
   
   // access the freshest typed values with get()
   val server = Server(config[server.port].get(), config[server.name].get())
   if (isSomethingOn.get()) {
       server.start()
   }

3. Also, you can add some complex logic that will execute every time the property is changed

   val port: Reloadable<Int> = config[server.port]
   
   port.onChange() {
       // for example, restart server
   }

Extending

Property Types

To add a custom property type, you should create an instance of PropertyType class and provide it with default property value and parse function.

Configuration Sources

To support a new configuration source, you should implement ConfigSource interface.

Contributors

• Dmitry Vologin - GitHub account
• Alexandra Osipova - GitHub account
• Anton Plotnikov - GitHub account
• Philipp Dolgolev - GitHub account

License

This project is licensed under the MIT License. The full text could be found in LICENSE.md.

Acknowledgments

• Inspired by Tinkoff ReactiveConfig and Konfig

Notes

• Rhea is one of the Titans in Greek mythology, the mother of the first generation of the Olympian gods
• Rhea's name is believed to be derived from the word ῥέω (rheo), meaning “flow” or “ease”