How to use JpaSpecificationExecutor in Spring?

1 year ago
Ava Mitchell
2 minutes

In Spring, JpaSpecificationExecutor is a sub-interface of JpaRepository that supports querying entity objects based on specified criteria.

In order to use JpaSpecificationExecutor, the first step is to define a query condition object that implements the Specification interface. The Specification interface includes two methods: toPredicate method for defining the query conditions, and method for defining the combination of multiple query conditions.

Here is an example demonstrating how to use JpaSpecificationExecutor:

  1. Firstly, define a query object that implements the Specification interface, for example:
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

public class UserSpecification implements Specification<User> {

    private String name;

    public UserSpecification(String name) {
        this.name = name;
    }

    @Override
    public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
        return criteriaBuilder.equal(root.get("name"), name);
    }
}
  1. Then inherit the JpaRepository and JpaSpecificationExecutor interfaces in the Repository, and use the Specification object in the methods that require querying, for example:
@Repository
public interface UserRepository extends JpaRepository<User, Long>, JpaSpecificationExecutor<User> {

    List<User> findAll(Specification<User> specification);

}
  1. Finally, in the Service or Controller, use the UserRepository to perform queries, for example:
@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public List<User> findUsersByName(String name) {
        Specification<User> spec = new UserSpecification(name);
        return userRepository.findAll(spec);
    }
}

In the example above, we defined a UserSpecification class to represent the search conditions based on the username. We then used the findAll method of UserRepository in UserService and passed in the UserSpecification object to perform the search.

It is important to note that the JpaSpecificationExecutor interface also provides other methods, such as findAll(Specification spec, Pageable pageable) for pagination queries, count(Specification spec) for counting the number of query results, and so on.

I hope the above information is helpful to you!

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