Load implementors of an interface into list with Spring

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Last week I wrote a blog post how to load complete inheritance tree of Spring beans into list. Similar feature can be used for autowiring all implementors of 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.

implementors

Now let’s load implementors 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.

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