Explore inheritance of `@LockMode` when defined on default interface methods

[ilia1243]

Let's assume we need a CrudRepository with two methods:

• findById with default behaviour
• findByIdForUpdate with LockModeType.PESSIMISTIC_WRITE

Naive way to implement it might be:

@Repository
interface MyRepository : CrudRepository<MyEntity, Long> {
    @Lock(LockModeType.PESSIMISTIC_WRITE)
    @Query("from MyEntity where id = :id")
    fun findByIdForUpdate(id: Long): Optional<MyEntity>
}

However, it produces two queries if called two times in the same transaction.

This can be avoided using Custom Repository Implementations https://docs.spring.io/spring-data/jpa/reference/repositories/custom-implementations.html and EntityManager.find(Class, Object, LockModeType).

What do you think about an out-of-box method such as CrudRepository.findById(ID, LockModeType) to support this?

[mp911de]

I'm not sure I follow. You can annotate findById with @Lock(LockModeType.PESSIMISTIC_WRITE) apply lock modes.

[ilia1243]

In this case there will be no findById with default behaviour without lock. The goal is to have two methods, with and without lock in the same repository.

[quaff]

I didn't test, but it maybe works:

    @JvmDefault
    @Lock(LockModeType.PESSIMISTIC_WRITE)
    fun findByIdForUpdate(id: Long) = findById(id)

[mp911de]

Using default methods doesn't work because we create CrudMethodMetadata for each method call. However, it would be a decent mechanism to inherit declarations.

[ilia1243]

Do you mean CrudMethodMetadataPostProcessor could check if some other method is already bound to transaction, and merge annotations if so?

https://github.com/spring-projects/spring-data-jpa/blob/4.0.4/spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/CrudMethodMetadataPostProcessor.java#L145