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

Question

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

No matching bean of type [SomeBe

Answer 1

If I add (required=false), I get null for beans.

Does the field get explicitly set to null or does it simply not get set at all? Try adding an initializer expression

@Autowired List<SomeBeanClass> beans = new ArrayList<>();

Answer 2

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.