如何在 Spring MVC 控制器中应用 Spring Data 投影? [英] How to apply Spring Data projections in a Spring MVC controllers?

问题描述

直接调用数据仓库方法时是否可以指定projection?这是存储库代码 - 请注意，我不想通过 REST 公开它，而是希望能够从服务或控制器调用它:

Is it possible to specify projection when calling data repository method directly? Here's repository code - note I would not like to expose it via REST, instead I would like to be able to call it from a service or controller:

@RepositoryRestResource(exported = false)
public interface UsersRepository extends PagingAndSortingRepository<User, Long> {

    @Query(value = "SELECT u FROM User u WHERE ....")
    public Page<User> findEmployeeUsers(Pageable p);
}

然后在控制器中我这样做:

Then in a controller I do this:

@PreAuthorize(value = "hasRole('ROLE_ADMIN')")
@RequestMapping(value = "/users/employee")
public Page<User> listEmployees(Pageable pageable) {
    return usersRepository.findEmployeeUsers(pageable);
}

当findEmployeeUsers 方法被直接调用时，有没有办法指定projection?

Is there any way to specify projection for findEmployeeUsers method when it is called directly like above?

我意识到上面的代码对于某些人来说可能看起来很奇怪……可以通过 REST 公开存储库并将 @PreAuthorize 东西放在存储库中.思想控制器更适合进行安全检查 - 它更自然，也更易于测试.

I realise that the code above might look odd for someone... it would be possible to expose the repository via REST and put the @PreAuthorize thing in the repository. Thought controller is the more right place to do security checks - it is more natural as well as simpler to test.

那么，projection 可以以某种方式传递到直接调用的存储库方法中吗?

So, can projection thing be somehow passed into a repository method called directly?

推荐答案

不，它不是，特别是因为投影通常根据具体情况应用于查询执行的结果.因此，它们目前被设计为有选择地应用于域类型.

No it's not, especially as projections are usually applied to the result of a query execution on a case by case basis. Thus they're currently designed to be selectively applied to domain types.

从最新的 Spring Data Fowler 发布系列 GA 发布开始，可以在 Spring MVC 控制器中以编程方式使用投影基础设施.只需为 SpelAwareProxyProjectionFactory 声明一个 Spring bean:

As of the latest Spring Data Fowler release train GA release the projection infrastructure can be used programmatically in Spring MVC controllers. Simply declare a Spring bean for SpelAwareProxyProjectionFactory:

@Configuration
class SomeConfig {

  @Bean
  public SpelAwareProxyProjectionFactory projectionFactory() {
    return new SpelAwareProxyProjectionFactory();
  }
}

然后将其注入您的控制器并使用它:

Then inject it into your controller and use it:

@Controller
class SampleController {

  private final ProjectionFactory projectionFactory;

  @Autowired
  public SampleController(ProjectionFactory projectionFactory) {
    this.projectionFactory = projectionFactory;
  }

  @PreAuthorize(value = "hasRole('ROLE_ADMIN')")
  @RequestMapping(value = "/users/employee")
  public Page<?> listEmployees(Pageable pageable) {

    return usersRepository.findEmployeeUsers(pageable).//
      map(user -> projectionFactory.createProjection(Projection.class, user);
  }
}

看看最新版本 Page 是如何有一个 map(…) 方法的，该方法可用于动态转换页面内容.我们使用 JDK 8 lambda 来提供使用 ProjectionFactory 的转换步骤.

See how as of the latest release Page has a map(…) method that can be used to transform the page content on the fly. We use a JDK 8 lambda to provide a conversion step using the ProjectionFactory.

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