Guice and general application configuration

Question

For a monitoring software written in Java I consider using Google Guice as DI provider. The project needs to load its configuration from an external resource (file or database).

Answer 1

I ran into the same problem in my own project. We had already chosen Guice as DI-framework and to keep things simple wanted to use it also with configuration.

We ended up reading the configuration from properties file using Apache Commons Configuration and binding them to Guice injector like suggested in Guice FAQ How do I inject configuration parameters?.

@Override public void configure() {
    bindConstant().annotatedWith(ConfigurationAnnotation.class)
        .to(configuration.getString("configurationValue"));    
}

Reloading of configuration supported by Commons Configuration is also quite easy implement into Guice injection.

@Override public void configure() {
    bind(String.class).annotatedWith(ConfigurationAnnotation.class)
        .toProvider(new Provider() {
            public String get() {
                return configuration.getString("configurationValue");
            }
    });    
}