如何在spring中使用JPA存储库从服务器检索blob

Question

我已经为CRUD创建了spring应用程序。我可以很容易地写入服务器数据，如字符串，长，blob，但当我试图从服务器检索它。我遇到了服务器的字节数组在服务器的BigInteger中给出的困难。我怎样才能在字节数组中获得数据而不是BigInteger？当我在插入字节数组中写入该数据时，该数据的列是BLOB。这是我的代码

储存库

public interface ArriveRepository extends JpaRepository<ArriveEntity,Long>
{ 
    @Query(value = "select arrive.time,air_lines.image,arrive.flight,arrive.destination_uzb," +
            "arrive.destination_eng,arrive.destination_rus,arrive.status,arrive.status_time " +
            "from arrive inner join air_lines on air_lines.id = arrive.airline_id where arrive.arrive_date = (:date1)",nativeQuery = true)
    List<Object[]> getForArriveTerminal(@Param("date1") LocalDate date1);
}

public class ArriveTerminalDto {
   private String time;
   private BigInteger logo;
   private String flight;
   private String destinationUzb;
   private String destinationEng;
   private String destinationRus;
   private String status;
   private String statusTime;
  //getter setter}

  public List<ArriveTerminalDto> getToShow(LocalDate date1)
    {
        List<ArriveTerminalDto> list = new ArrayList<>();
        List<Object[]> list1 = arriveRepository.getForArriveTerminal(date1);
        for(Object[] objects: list1)
        {
            ArriveTerminalDto arriveTerminalDto = new ArriveTerminalDto();
            arriveTerminalDto.setTime((String)objects[0]);
            arriveTerminalDto.setLogo((BigInteger) objects[1]);
            arriveTerminalDto.setFlight((String) objects[2]);
            arriveTerminalDto.setDestinationUzb((String) objects[3]);
            arriveTerminalDto.setDestinationRus((String) objects[4]);
            arriveTerminalDto.setDestinationEng((String) objects[5]);
            arriveTerminalDto.setStatus((String) objects[6]);
            list.add(arriveTerminalDto);
        }
        return list;
    }

{
    "timestamp": "2019-01-28T09:33:52.038+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "java.math.BigInteger cannot be cast to [B",
    "path": "/arrive/terminal/date=2019-01-27"
}

public interface ArriveRepository extends JpaRepository<ArriveEntity,Long>
{

    @Query(value = "select arrive.time,air_lines.image,arrive.flight,arrive.destination_uzb," +
            "arrive.destination_eng,arrive.destination_rus,arrive.status,arrive.status_time " +
            "from arrive inner join air_lines on air_lines.id = arrive.airline_id where arrive.arrive_date = (:date1)",nativeQuery = true)
    List<ArriveTerminalDto> getForArriveTerminal(@Param("date1") LocalDate date1);
}

Answer 1

你为什么不看一下Spring内容社区项目。该项目允许您将内容与Spring数据实体相关联。想想Spring数据，但对于内容，或者非结构化数据。这也可以为内容提供RESTendpoint，比如Spring Data REST。

这种方法将为您的内容提供一个清晰的抽象，并为许多不同类型的存储提供实现。它是基于流的，而不是基于字节的。如果要传输非常大的文件，使用Byte[]是行不通的。另外，使数据库正确地流化是非常特殊的。当Spring Content已经完成时，您可能不想自己解决所有这些问题。

这很容易添加到现有的项目中。我不确定你是否在使用Spring Boot。我将举一个非Spring Boot示例：

pom.xml

   <!-- Java API -->
   <dependency>
      <groupId>com.github.paulcwarren</groupId>
      <artifactId>spring-content-jpa</artifactId>
      <version>0.5.0</version>
   </dependency>
   <!-- REST API (if you want it) -->
   <dependency>
      <groupId>com.github.paulcwarren</groupId>
      <artifactId>spring-content-rest</artifactId>
      <version>0.5.0</version>
   </dependency>

配置

@Configuration
@EnableJpaStores
@Import("org.springframework.content.rest.config.RestConfiguration.class")
public class ContentConfig {

    // schema management
    // 
    @Value("/org/springframework/content/jpa/schema-drop-mysql.sql")
    private Resource dropContentTables;

    @Value("/org/springframework/content/jpa/schema-mysql.sql")
    private Resource createContentTables;

    @Bean
    DataSourceInitializer datasourceInitializer() {
        ResourceDatabasePopulator databasePopulator =
                new ResourceDatabasePopulator();

        databasePopulator.addScript(dropContentTables);
        databasePopulator.addScript(createContentTables);
        databasePopulator.setIgnoreFailedDrops(true);

        DataSourceInitializer initializer = new DataSourceInitializer();
        initializer.setDataSource(dataSource());
        initializer.setDatabasePopulator(databasePopulator);

        return initializer;
    }
}

@Entity
public class ArriveEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    .. existing fields...    


    @ContentId
    private String contentId;

    @ContentLength
    private long contentLength = 0L;

    // if you have rest endpoints
    @MimeType
    private String mimeType = "text/plain";
}

@StoreRestResource(path="arriveEntityContent)
public interface ArrivEntityContentStore extends ContentStore<ArriveEntity, String> {
}

要使用Java API访问内容，请自动连接ArriventyContentStore并使用它的方法。

或者使用REST API访问内容：

curl-x POST/arriveentitycontent/{arriveEntityId}

HTH