Java Generics and Annotations: Type-Safe

Question

I know that I can do something like:

public class AbstractDao<T extends Bean> {

}

In this case, Bean is an class or interface.

I was wondering if is there a way to do this with annotations, like:

public class AbstractDao<T extends javax.persistence.Entity> {

}

Is something like this possible?

Thanks in advance!

score 4 · Accepted Answer · edited May 23 '17 at 12:16

4

Unfortunately, there is no inheritance in annotations, so it's not possible.

Have a look at the answers to the similar question here:

Why is not possible to extend annotations in Java?

edited May 23 '17 at 12:16

Community

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answered Apr 06 '12 at 18:55

John Farrelly

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score 4 · Answer 2 · answered Apr 06 '12 at 19:04

No. The Java Language Specification says that type variables can only be constrained to extend / implement particular classes or interfaces. Since annotating a class does not cause the class to extend or implement a particular type, you can't constrain by annotation.

Java Generics and Annotations: Type-Safe

2 Answers2