hibernate - 如何在 Spring Boot Data Jpa 应用程序中使用条件查询

Question

我有一个使用 Spring Boot Data jpa 的应用程序。
到目前为止，我正在使用这样的存储库

public interface StudentRepository extends CrudRepository<StudentEntity, Integer>{
    @Query(value = "" 
        + "SELECT s.studentname "
        + "FROM   studententity s, "
        + "       courseentity c "
        + "WHERE  s.courseid = c.courseid "
        + "       AND s.courseid IN (SELECT c.courseid "
        + "                          FROM   courseentity c "
        + "                          WHERE  c.coursename = ?1)")
    List<String> nameByCourse(String coursename);
}

我如何在 Spring Boot 应用程序中使用 Hibernate 为此类情况提供的 Criteria Query

Answer 1

来自 docs

To enrich a repository with custom functionality you first define an interface and an implementation for the custom functionality. Use the repository interface you provided to extend the custom interface.

像这样定义一个接口(interface)

public interface StudentRepositoryCustom {

    List<String> nameByCourse(String coursename);

}

然后像这样定义这个接口(interface)的自定义实现

@Service
class StudentRepositoryImpl implements StudentRepositoryCustom {

    @PersistenceContext
    private EntityManager em;

    public List<String> nameByCourse(String coursename) {            
        CriteriaBuilder cb = em.getCriteriaBuilder();
        //Using criteria builder you can build your criteria queries.
    }

}

现在，您可以像这样在您的 JPA 存储库中扩展此自定义存储库实现。

public interface StudentRepository extends CrudRepository<StudentEntity, Integer>, StudentRepositoryCustom {

}

了解有关条件查询和条件构建器的更多信息 here