从未通过ID找到的Spring Data JPA实体

Question

I am using spring data jpa , spring boot and h2 database.

My repository looks like this

public interface IComponentStorageRepository extends JpaRepository<ComponentData, String> {
}

My domain object looks like this

@Entity
@Table(name = "component_data")
public class ComponentData {
    @Column(name = "component_id")
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private String componentId;
    private String description;

with overriden equals and hashcode .

I have a service method that looks like this.

@Override
public void updateComponent(String componentId, String description) {
    if (repository.existsById(componentId)) {
        ComponentData stored = repository.getOne(componentId);
        stored.setDescription(description);
        repository.saveAndFlush(stored);
    } else {
        ComponentData stored = new ComponentData();
        stored.setComponentId(componentId);
        stored.setDescription(description;
        repository.saveAndFlush(newResult);
    }
}

It firstly performs a check if the object exists (to prevent EntityNotFound exception) and then is trying to read one. If no object found it supposed to create a new one.

But each time I am trying to invoke the method - it is never able to find the entity. Every time it creates a new one.

I originally used repository.save and had @Transactional over the method but it didn't help either. I also haven't specified any properties and use everything default.

What is the problem

Answer 1

@GeneratedValue(strategy = GenerationType.IDENTITY ) can't be used with String type and what i know it's not supported by the H2 inmemory DB.

When you want to use the key as String you have to assign it manually before persisting without @GeneratedValue anotation or define the @GeneratedValue for String type properly.

There is an example from @VladMichalcea https://vladmihalcea.com/hibernate-and-uuid-identifiers/ .

Another option would be to change the type of the primary key to be @GeneratedValue supported types long (Long), int(Integer).