JpaRepository - 删除方法 - 通知实体不存在

Question

During delete operation, can a JpaRepository inform me, that entity I want to remove does not exists ?

I know that delete methods doesn't returns boolean value, and also doesn't throws Exceptions .

I also know that I can just simply do exists() or findOne() and then perform delete, but I'm just curious.

Is there any way to force this?

I'm using Spring Boot 1.5.1. Sample code below:

public HttpStatus deleteEventByTitle(String eventTitle) {
    try {
        eventRepository.deleteByTitle(eventTitle);
    } catch (EntityNotFoundException e) { // just showing what I want to do
        return HttpStatus.NOT_FOUND;
    }
    return HttpStatus.OK;
}


public interface EventRepository extends JpaRepository<Event, Long> {

    void deleteByTitle(String title);

}

Answer 1

Starting from Spring Data JPA (>=1.7.x), we can use the derived delete or remove query. It can return the number of entities deleted or what all entities are deleted.

Using it we can update our code as:

public interface EventRepository extends JpaRepository<Event, Long> {
    long deleteByTitle(String title);
}

and we can throw an exception if the entity doesn't exist.

public HttpStatus deleteEventByTitle(String eventTitle) {
    long numOfEntriesDeleted = eventRepository.deleteByTitle(eventTitle);
    if(numOfEntriesDeleted != 1){
       return HttpStatus.NOT_FOUND;
    }
    return HttpStatus.OK;
}

Answer 2

According to the spec this is not possible and I am not aware of a functionality like this.

I know that when working with Cassandra and Datastax you can check wasApplied() .

The only way around would be to implement your own deleteOrThrowException -method and throw an exception in case you didn't find the entity.

In order to achieve this you could add a

@Query("select count(event)>0 from Event e where eventTitle := eventTitle")
public boolean existsByTitle(String eventTitle);

Answer 3

You can simply check if it exists before deleting it:

// Check if the ID is available
if (deviceRepository.existsById(id)) {
    deviceRepository.deleteById(id);
    //returnObject.setMessage("Deleted successfully !!");

} else {
    //returnObject.setMessage("The ID is not found");
}