Inject parameter only when it's useful, otherwise default

Asked Mar 07 '18 at 10:19

Active Mar 07 '18 at 10:56

Viewed 55 times

I couldn't find a satisfying answer to this anywhere, links are appreciated.

In Guice, suppose I create a Frobnifier that takes an integer parameter velocity that tells it how fast to frobnify things:

public class Frobnifier {
  @Inject
  public Frobnifier(@FrobnificationSpeed Integer velocity) {
    // ...
  }
}

Now suppose I'd like this value to be 5 by default, but I'd also like to enable clients to override this value at injection time if they feel like it should be something else.

What is the Guice best practice here? Should I create a module for this class and install it in other modules?

asked Mar 07 '18 at 10:19

vinntec

Provide a default value for FrobnificationSpeed annotation? – Thiyagu Mar 07 '18 at 10:21
Do you have an example? – vinntec Mar 07 '18 at 10:27
Can you show you FrobnificationSpeed interface? – Thiyagu Mar 07 '18 at 10:27
`public @interface FrobnificationSpeed { }` – vinntec Mar 07 '18 at 10:28
Have a look at one of my answers - https://stackoverflow.com/questions/49010954/guice-inject-annotation-value/49013060#49013060. But I'm not sure if it is the best way though – Thiyagu Mar 07 '18 at 10:30
Ideally It'd be best if Frobnifier clients didn't have to specify the speed, but could if they so wished – vinntec Mar 07 '18 at 10:35
So, what if you have an element in the `FrobnificationSpeed` like `int speed() default 5;`? – Thiyagu Mar 07 '18 at 10:42
https://google.github.io/guice/api-docs/4.2/javadoc/com/google/inject/multibindings/OptionalBinder.html – Tavian Barnes Mar 09 '18 at 17:31

Inject parameter only when it's useful, otherwise default

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