How to beautifully update a JPA entity in Spring Data?

Solution 1:

Even better then @Tanjim Rahman answer you can using Spring Data JPA use the method T getOne(ID id)

Customer customerToUpdate = customerRepository.getOne(id);
customerToUpdate.setName(customerDto.getName);
customerRepository.save(customerToUpdate);

Is's better because getOne(ID id) gets you only a reference (proxy) object and does not fetch it from the DB. On this reference you can set what you want and on save() it will do just an SQL UPDATE statement like you expect it. In comparsion when you call find() like in @Tanjim Rahmans answer spring data JPA will do an SQL SELECT to physically fetch the entity from the DB, which you dont need, when you are just updating.

Solution 2:

In Spring Data you simply define an update query if you have the ID

  @Repository
  public interface CustomerRepository extends JpaRepository<Customer , Long> {

     @Query("update Customer c set c.name = :name WHERE c.id = :customerId")
     void setCustomerName(@Param("customerId") Long id, @Param("name") String name);

  }

Some solutions claim to use Spring data and do JPA oldschool (even in a manner with lost updates) instead.

Solution 3:

This is more an object initialzation question more than a jpa question, both methods work and you can have both of them at the same time , usually if the data member value is ready before the instantiation you use the constructor parameters, if this value could be updated after the instantiation you should have a setter.

Solution 4:

If you need to work with DTOs rather than entities directly then you should retrieve the existing Customer instance and map the updated fields from the DTO to that.

Customer entity = //load from DB
//map fields from DTO to entity

Solution 5:

So now assume the Customer wants to change his name in the webui - then there will be some controller action, where there will be the updated DTO with the old ID and the new name.

Normally, you have the following workflow:

1. User requests his data from server and obtains them in UI;
2. User corrects his data and sends it back to server with already present ID;
3. On server you obtain DTO with updated data by user, find it in DB by ID (otherwise throw exception) and transform DTO -> Entity with all given data, foreign keys, etc...
4. Then you just merge it, or if using Spring Data invoke save(), which in turn will merge it (see this thread);

P.S. This operation will inevitably issue 2 queries: select and update. Again, 2 queries, even if you wanna update a single field. However, if you utilize Hibernate's proprietary @DynamicUpdate annotation on top of entity class, it will help you not to include into update statement all the fields, but only those that actually changed.

P.S. If you do not wanna pay for first select statement and prefer to use Spring Data's @Modifying query, be prepared to lose L2C cache region related to modifiable entity; even worse situation with native update queries (see this thread) and also of course be prepared to write those queries manually, test them and support them in the future.