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For example annotate a field for apply some kind of data validation, it’s a good thing?

Its highly dependant on the context. You will have to use reflection which may be slow.
Data validation might be better achieved by setters.

Thanks, I start to write a library for model validation using Annotation and Reflection, my fear is the performance of reflection process, but is an experiment 

As far as I remember, Spring boot also uses Annotations for validation. It might be a good reference to look into...

<https://www.baeldung.com/javax-validation>

It’s quite standard on the Java server side