ObjectProvider Map resolution inconsistency between resolveDependency and getBeanProvider [SPR-17577]

[spring-projects-issues]

Dave Syer opened SPR-17577 and commented

DefaultListableBeanFactory has 2 methods that can be used to extract an ObjectProvider, and they behave inconsistently if the dependency is of type Map<String,X>. Here's a test that fails:

@SpringBootTest
@RunWith(SpringRunner.class)
public class SampleApplicationTests {

	@Autowired
	public ObjectProvider<Map<String, Bar>> provider;

	@Autowired
	private Bar bar;

	@Autowired
	private DefaultListableBeanFactory beans;

	@Test
	public void test() {
		assertThat(bar).isNotNull();
	}

	@Test
	public void fails() {
		ObjectProvider<Map<String, Bar>> provider = beans.getBeanProvider(
				ResolvableType.forClassWithGenerics(Map.class, String.class, Bar.class));
		assertThat(provider.getIfAvailable()).isNotEmpty();
	}

	@Test
	public void auto() {
		assertThat(provider.getIfAvailable()).isNotEmpty();
	}

	@Test
	public void descriptor() {
		DependencyDescriptor descriptor = new DependencyDescriptor(
				ReflectionUtils.findField(SampleApplicationTests.class, "provider"),
				true);
		@SuppressWarnings("unchecked")
		ObjectProvider<Map<String, Bar>> provider = (ObjectProvider<Map<String, Bar>>) beans
				.resolveDependency(descriptor, "test");
		assertThat(provider.getIfAvailable()).isNotEmpty();
	}

}

@SpringBootConfiguration
class SampleConfiguration {

	@Bean
	public Foo foo() {
		return new Foo();
	}

	@Bean
	public Bar bar(Map<String, Foo> foo) {
		return new Bar(foo.values().iterator().next());
	}

}

class Bar {

    private final Foo foo;

    public Bar(Foo foo) {
        this.foo = foo;
    }

    public Foo getFoo() {
        return this.foo;
    }
}

class Foo {

    private String value;

    public Foo() {
    }

    public Foo(String value) {
        this.value = value;
    }

    public String getValue() {
        return this.value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Foo [value=" + this.value + "]";
    }

}

---

Affects: 5.1.3

[spring-projects-issues]

Juergen Hoeller commented

This is by design: Resolution of Collection or Map as a collection of individual beans is only supported for declarative injection points. Such resolution is ambiguous with beans which are of type Collection or Map themselves, and it's convoluted enough that we have to support this for annotation-based resolution still. For ObjectProvider usage and even more so for plain programmatic usage, the recommended way to access multiple beans is through the ObjectProvider's iteration/stream access operators, with the declared bean type always indicating the individual bean type to match.

In any case, we need to document this properly, so I'm turning this into a documentation ticket.

[spring-projects-issues]

Dave Syer commented

There's no way to access the bean names from an ObjectProvider is there? So there is no direct replacement in the functional approach? I guess there is always getBeansOfType(). I assume they didn't want to use that in Boot for some reason (see spring-projects/spring-boot#15419).

[spring-projects-issues]

Juergen Hoeller commented

Indeed, if you need the bean names as well, an on-demand call to getBeansOfType is a solution... or getBeanNamesForType plus individual getBean calls as the recommended variant.

[spring-projects-issues]

Juergen Hoeller commented

It turns out that there is a corresponding note in the getBeanProvider(ResolvableType) javadoc already.