Is there an easy way to autowire empty collection if no beans present in Spring?

Question

If I have @Autowired List<SomeBeanClass> beans; and no beans of SomeBeanClass, I get:

No matching bean of type [SomeBeanClass] found for dependency [collection of SomeBeanClass]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

If I add (required=false), I get null for beans. But it looks like error prone solution requiring null checks.

Is there an easy way (one liner) to autowire empty collection if no beans present?

Answer 1

There are a few options with Spring 4 and Java 8:

@Autowired(required=false) private List<Foo> providers = new ArrayList<>(); 

You can also use java.util.Optional with a constructor:

@Autowired public MyClass(Optional<List<Foo>> opFoo) {     this.foo = opFoo.orElseGet(ArrayList::new); } 

You should also be able to autowire an a field with Optional<List<Foo>> opFoo;, but I haven't used that yet.