Load All Implementors of an Interface into List with Spring

last week i wrote a blog post how to load complete inheritance tree of spring beans into list . a similar feature can be used for autowiring all implementors of a certain interface.

let’s have this structure of spring beans. notice that bear is abstract class, therefore it’s not a spring bean. so we have three beas: wolf, polarbear and grizzly.

in following snippet are all implementors loaded into list with constructor injection:

@service
public class nature {
	list<runner> runners;

	@autowired
	public nature(list<runner> runners) {
		this.runners = runners;
	}

	public void showrunners() {
		runners.foreach(system.out::println);
	}
}

method showrunners is using java 8 foreach method that consumes method reference.  this construct outputs loaded beans into console. you would find a lot of reading about these new java 8 features these days.

spring context is loaded by this main class:

public class main {
	public static void main(string[] args) {
		annotationconfigapplicationcontext context =
			new annotationconfigapplicationcontext(springcontext.class);
		nature nature = context.getbean(nature.class);
		nature.showrunners();
	}
}

console output:

polarbear []
wolf []
grizzly []

this feature can be handy sometimes. source code of this short example is on github .