java CDI@Instance收集@Any，但访问限定符（特别是@Named）

Question

我想收集某处出产的所有豆子。大概是这样的：

static class Greeting {
    public final String text;

    public Greeting(String text) {
        this.text = text;
    }
}

@Produces
@Named("hi")
Greeting hi = new Greeting("Hi");

@Produces
@Named("hello")
Greeting hello = new Greeting("Hello");

@Inject
Instance<Greeting> greetings;


@Test
public void shouldCollectAll() {
    Set<String> set = new HashSet<>();
    for (Greeting greeting : greetings) {
        set.add(greeting.text);
    }
    assertEquals(2, set.size());
    assertTrue(set.contains("Hi"));
    assertTrue(set.contains("Hello"));
}

我知道我可以选择以下限定符：

@SuppressWarnings("all")
private static class NamedLiteral extends AnnotationLiteral<Named> implements Named {
    private final String name;

    public NamedLiteral(String name) {
        this.name = name;
    }

    @Override
    public String value() {
        return name;
    }
}

@Test
public void shouldCollectNamedHi() {
    Greeting greeting = greetings.select(new NamedLiteral("hi")).get();
    assertEquals("Hi", greeting.text);
}

但我想进入资格赛。比如：

@Test
public void shouldCollectAllWithMeta() {
    Map<String, Greeting> map = new HashMap<>();
    for (Greeting greeting : greetings) {
        Annotated annotated = magic(greeting);
        String name = annotated.getAnnotation(Named.class).value();
        map.put(name, greeting);
    }
    assertEquals(2, map.size());
    assertEquals("Hi", map.get("hi"));
    assertEquals("Hello", map.get("hello"));
}

有没有一种方法可以在不编写CDI扩展的情况下实现magic？还是外面有一个？或者这是对CDI2.0的功能要求

Answer 1

无法从bean上下文实例访问bean元数据。然而，当在bean本身的级别工作时，使用BeanManager实例并且不编写CDI扩展时，这是可能的，例如：

@Inject
BeanManager manager;

Set<Bean<?>> beans = manager.getBeans(Greeting.class, Named.class);

for (Bean<?> bean : beans) {
    String name = getQualifierOfType(bean.getQualifiers(), Named.class).value();
    map.put(name, greeting);
}

<Annotation, T extends Annotation> T getQualifierOfType(Set<Annotation> qualifiers, Class<T> type) {
    for (Annotation qualifier : qualifiers)
        if (type.isAssignableFrom(qualifier.getClass()))
            return type.cast(qualifier);

    return null;
}