How can I pass a method into a functional interface for a retry and have it be generic?

Question

I want to a create a functional interface or default method where I pass in a jpa repository method such as findById or findByNumber and have it return a generic type; this way I annotate it with @Retryable if the application fails to connect to db. Below are examples of methods I want passed through the functional interface:

Employee employee = repository.findById("2ed21");
Record record = repository.findbyNumber(311);

There seems to be some duplicate text in your question, but more importantly, you haven't asked one. Where are you stuck? Please read [ask]. — tgdavies, Aug 09 '23 at 22:16
Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. — Community, Aug 10 '23 at 14:26

score 1 · Accepted Answer · answered Aug 23 '23 at 03:39

How about a simple method with a Supplier as a parameter where you can put literally anything?

@Retryable(...)
public <T> T retry(Supplier<T> supplier) {
    return supplier.get();
}

Usage:

Employee employee = retry(() -> repository.findById("2ed21"));
Record record = retry(() -> repository.findbyNumber(311));

Few notes:

You need to invoke a method annotated with @Retryable from a different bean to overcome a limitation of Spring AOP. To be honest I have never worked with @Retryable but I guess it would work the same way as @Transactional, related: Spring @Transaction method call by the method within the same class, does not work?
I haven't tested the solution.

Thanks for reply. That's what I end up doing. – Wes Aug 23 '23 at 21:28 — Wes, Aug 23 '23 at 21:28

How can I pass a method into a functional interface for a retry and have it be generic?

1 Answers1