Spring Boot - 查询方法公共抽象 java.util.stream.Stream

Question

我需要流式传输对象列表，但是当我使用 JpaRepository 和 @Query 尝试它时，我收到此异常：

Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'MainApplication': Unsatisfied dependency expressed through field 'service'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'MyServiceImpl': Unsatisfied dependency expressed through field 'myDAO'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'MyDAO': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.stream.Stream com.my.package.dao.MyDAO.streamAll()!

MyDAO 代码：

@Repository

public interface MyDAO extends JpaRepository<MyEntity, Long> {

    @QueryHints(value = @QueryHint(name = HINT_FETCH_SIZE, value = "" + 

        Integer.MIN_VALUE))

    @Query(value = "SELECT m FROM MyEntity m")

    Stream<MyEntity> streamAll();

    ...

}

主要代码：

@SpringBootApplication

@ComponentScan("com.my.package.*")

@EntityScan("com.my.package.*")

@Configuration

@EnableAutoConfiguration

public class MainApplication implements CommandLineRunner {

    @Autowired

    MyServiceInterface service;

    public static void main(String[] args) {

        SpringApplication.run(MainApplication.class, args);

    }

    @Override

    public void run(String... args) throws Exception {

        try {

            service.createCsv();

        } catch (RuntimeException e) {

            System.out.println(e);

        }

    }

}

我已经尝试了一切，但没有任何效果，请帮助我！

Answer 1

您将无法使用，Stream<MyEntity> findAll();因为JpaRepository已经定义了具有List返回类型的方法，因此您可以像这样重命名方法Stream<MyEntity> getAll();或使用 Ordering 将方法重命名为Stream<MyEntity> findAllByOrderByIdAsc();.

Answer 2

只需删除@Query(value&nbsp;=&nbsp;"SELECT&nbsp;m&nbsp;FROM&nbsp;MyEntity&nbsp;m")并使用 JPARepository 的 findAll() 方法，如下所示Stream<MyEntity>&nbsp;findAll();