Cool, I’ll be able to sleep tonight :)
On 09 Apr 2014, at 21:19, Gunnar Morling <gun...@hibernate.org> wrote:
> 2014-04-09 21:01 GMT+02:00 Emmanuel Bernard <emman...@hibernate.org>:
> I always thought that type annotations would allow us to look via
> refection to annotations like
>
> public class Foo {
> public Set< @NotNull String> names;
> }
>
> But looking at some tutorials like
> http://jaxenter.com/jsr-308-explained-java-type-annotations-49929.html
>
> it seems that these annotations are only "visible" to a compiler plug-in
> / processor.
>
> Am I right?
>
> No, one can access type annotations at runtime (at least for fields, method
> signatures and so on) via reflection. A while ago I feared the same, so I
> asked on core-libs-dev [1] and got confirmation that it's possible. That's
> how you'd do it:
>
> // given
> private List<@NotNull String> names;
> Field namesField = ...;
>
> // List<String>
> AnnotatedParameterizedType type = (AnnotatedParameterizedType)
> namesField.getAnnotatedType();
>
> // String
> AnnotatedType typeArg = type.getAnnotatedActualTypeArguments()[0];
>
> // @NotNull
> Annotation annotation = typeArg.getAnnotations()[0];
>
> It's one of the planned tasks of the HV GSoC project to make use of this to
> support constraints as in your example.
>
> If that turns out true that would suck as it would only be useful to
> static tools. I wish I had checked the spec earlier to influence it :(
>
> Emmanuel
>
> --Gunnar
>
> [1]
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-March/025732.html
>
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