Return List<String> or String in hibernate query without query annotation-CodePudding

I am using Spring Boot application. I am using following method to return List<String> using @Query

annotation.

@Query("select c.name from Customer c")
List<String> findAllNames();

Is there a way to get the above result without @Query or @NativeQuery annotations?

CodePudding user response：

Spring Data JPA supports this quite well. You can define a POJO that represents the (reduced) object (the projection) you want of the entity, then define a method that describes the query, returns the appropriate type, and Spring Data will generate all the code necessary to execute the query and map the results.

Here's an example of a custom repository interface that uses this technique (untested pseudo-code):

public class CustomerSummary {
    private String name;
    // constructor and getters
}

@Repository
public interface CustomerRepository extends CrudRepository<Customer, Long> {
    List<CustomerSummary> getAllSummaries();
}

I'm not sure if you can use "simple" types such as String in the return type, but I wouldn't be surprised if that is supported.

Also, you might have to tweak the exact method naming of `` to make sure Spring Data correctly interprets it as you want. Here is some additional reference documentation.

CodePudding user response：

You could use projection to select only name property:

interface CustomerNameProjection {
   String getName();
}

and then use it in Repository class:

List<CustomerNameProjection> findAllProjectedBy();

edit: corrected repository method name

CodePudding user response：

Inject EntityManager and call createQuery.

entityManager.createQuery("select c.name from Customer c")
    .getResultList()