Using Annotations for Metadata

Annotations are Java’s primary metadata mechanism because they can do more than marker interfaces.

Why Annotations Usually Win

Annotations can:

• target classes, methods, fields, parameters, and more
• carry configuration data
• be processed at compile time or runtime
• integrate naturally with frameworks

That makes them a better fit for modern Java libraries and platforms.

Practical Examples

• @Override for compiler-checked intent
• validation annotations such as @NotNull
• framework configuration such as Spring stereotypes
• custom metadata for tooling or runtime policies

Review Rule

If the meaning is metadata rather than type identity, annotations are usually the stronger choice.