jpa - : getSingleResult, 或 getResultList JPA 哪个更好

Question

我需要从表中检索单行，我对哪种方法更好感兴趣。
一侧getSingleResult专为检索单个结果而设计，但会引发异常。此方法是否对与 getResultList 相关的性能有好处？和

query.setFirstResult(0);
query.setMaxResults(1); 

Answer 1

根据 Joshua Bloch 的 Effective Java:

Use checked exceptions for conditions from wich the caller can reasonably be expected to recover. Use runtime exceptions to indicate programming errors.

归功于来源: Why you should never use getSingleResult() in JPA

@Entity
@NamedQuery(name = "Country.findByName", 
            query = "SELECT c FROM Country c WHERE c.name = :name"
public class Country {
  @PersistenceContext
  transient EntityManager entityManager;

  public static Country findByName(String name) {
      List<Country> results = entityManager
            .createNamedQuery("Country.findByName", Country.class)
            .setParameter("name", name).getResultList();
      return results.isEmpty() ? null : results.get(0);
  }
}