How to register Ratpack's ConfigurableModule using application configuration

Question

Current HikariModule contains hard-coded value in Java code, which is not a good practice, much better would be use values defined in db.properties. How to achieve this? Do I need create a custom ConfigurableModule<MyModule.Settings> and register HikariModule inside MyModule? I have not found the way how to register a module inside a module. Thanks!

public class App {

    public static void main(String[] args) throws Exception {
        RatpackServer.start(s -> s 
             .serverConfig( configBuilder -> configBuilder
                .findBaseDir()
                .props("db.properties")
                .require("/database", Settings.class)
             )
             .registry(Guice.registry( bindings -> bindings
                     .module(HikariModule.class, hm -> {
                         hm.setDataSourceClassName("org.postgresql.ds.PGSimpleDataSource");
                         hm.addDataSourceProperty("url", "jdbc:postgresql://localhost:5433/ratpack");
                         hm.setUsername("postgres");
                         hm.setPassword("postgres");
                     }).bind(DatabaseInit.class)
             ))
             .handlers( chain -> chain
                    ...
             )
        ); 
    }
}

Answer 1

Let's say you have a postgres.yaml file in src/ratpack/postgres.yaml whose contents are:

db:
  dataSourceClassName: org.postgresql.ds.PGSimpleDataSource
  username: postgres
  password: password
  dataSourceProperties:
    databaseName: modern
    serverName: 192.168.99.100
    portNumber: 5432

In that same directory let's say you have an empty .ratpack file.

From your main class you can then do this:

RatpackServer.start(serverSpec -> serverSpec
      .serverConfig(config -> config
        .baseDir(BaseDir.find()) // locates the .ratpack file
        .yaml("postgres.yaml") // finds file relative to directory containing .ratpack file
        .require("/db", HikariConfig.class) // bind props from yaml file to HikariConfig class
      ).registry(Guice.registry(bindings -> bindings
        .module(HikariModule.class) // this will use HikariConfig to configure the module
      )).handlers(...));

There's a full working example here https://github.com/danhyun/modern-java-web