Java Generics .class

Question

We have an annotation @Accepts:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Accepts {
  Class[] value();
}

It takes a list of Classes. These are later used to validate in a DSL that a field was passed an instance of the classes listed as acceptable.

Some examples of this annotation in use:

public enum PropertyName {


  @Accepts({Integer.class})
  xCoordinate,


  @Accepts({Integer.class})
  yCoordinate,

  @Accepts({Boolean.class})
  showPermission

  @Accepts({String.class, FieldScript.class, List.class})
  onClick

  /* And So On*/
}

I am adding a new item to this enum called 'value' and it can accept a String or a PropertyResolver. PropertyResolver is an interface defined as below:

public interface PropertyResolver<T> {
    public T getValue(TagContext tagContext);
}

I don't know how to do a .class on PropertyResolver to pass on to @Accepts. Is it possible to do so?

Thanks.

Bhesh Gurung · Accepted Answer · 2014-05-11 13:46:45Z

4

You will have to do PropertyResolver.class. There will only one Class instance that represents the the class (raw-version).

No such things as PropertyResolver<T>.class or PropertyResolver<Integer>.class exist.

Always, keep in mind that in Java, generics is compile time only feature.

edited May 11, 2014 at 13:46

answered May 9, 2014 at 21:56

Bhesh Gurung

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3 Comments

awksp Over a year ago

@JakubJirutka Wait, really? When are generics not erased?

awksp Over a year ago

Hmmm, found something that says that dynamic types are erased, but static types are not. Is that what you were referring to?

awksp Over a year ago

@JakubJirutka Ah, that's interesting. Thanks for the info! Learned something new today.

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