Explicitly calling a default method in java - when the implemented interface uses generics

Question

This questions is the same as this one with a twist.

I have an interface such as :

@Repository
public interface InvoiceRepository extends JpaRepository<Invoice, String>{

  // some other methods here 

 default Invoice save(Invoice invoice) {

        //I do sth here

        return JpaRepository.super.save(invoice); // wonT work
    }

}

How can i call the save method of the implemented JPA interface?

Update: Indeed i noticed, save is not a default in the extended JPARepository interface

In this case, what would be the best way of achieving this ?

override save method
call the parent save method in the overridden method

davidxxx · Accepted Answer · 2018-09-04 16:23:50Z

3

The default method you defined is helpless as Spring will implement out of the box a method with the same erasure (see CrudRepository.save()).

Here you don't invoke a default method of an interface :

JpaRepository.super.save(invoice);

you invoke the abstract save() method of CrudRepository.
But it cannot compile as it is abstract.
It could work as in the quoted question if the JpaRepositorysuper class defined a default save() method but that is not the case.

In this case, what would be the best way of achieving this ?

You could create a default method with a distinct name and from it call save() that at runtime will invoke the runtime InvoiceRepository instance :

default Invoice saveInvoice(Invoice invoice) {
    // I do sth here
    ...
    return save(invoice); 
}

edited Sep 4, 2018 at 16:23

answered Sep 4, 2018 at 16:05

davidxxx

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Comments

Naman · Accepted Answer · 2018-09-04 16:11:54Z

2

In your case, the method save() is not default. From the code, its defined as :

<S extends T> S save(S var1); // abstract, public

Note - Worth mentioning, the code belongs to the artifact org.springframework.data:spring-data-jpa:2.0.9.RELEASE.

Or if I could say, your inference is incorrect, "default is not implied by default."

edited Sep 4, 2018 at 16:11

answered Sep 4, 2018 at 16:08

Naman

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1 Comment

Orkun Over a year ago

indeed i noticed, save is not a default in the JPARepository interface

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