Question

Is there a way in Spring that I can auto populate a list with all of beans of a type AND any of its subtypes? I have a setter method that looks like:

setMyProp(List<MyType> list)

And I would like to autowire in any beans of MyType and all subclasses of MyType.

Thanks,
Jeff

Answer 1

Yup, you can do this. The spring docs say:

It is also possible to provide all
beans of a particular type from the
ApplicationContext by adding the
annotation to a field or method that
expects an array of that type.

Note that it says you need to expect an array, not a list. This makes sense, because generic type erasure means a list may not work at runtime. However, take the following unit test, which works:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">  

    <bean class="test.Test.TypeB"/>
    <bean class="test.Test.TypeC"/>
    <bean class="test.Test.TypeD"/>
</beans>

and this unit test:

package test;

@ContextConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
public class Test {

    private @Autowired List<TypeA> beans;

    @org.junit.Test
    public void test() {
        assertNotNull(beans);
        assertEquals(2, beans.size());
        for (TypeA bean : beans) {
            assertTrue(bean instanceof TypeA);
        }
    }       

    public static interface TypeA {}
    public static class TypeB implements TypeA {}
    public static class TypeC extends TypeB {}
    public static class TypeD {}

}

So officially, you’re supposed to autowire TypeA[], not List<TypeA>, but the List works good.