Spring WebFlux:从控制器提供文件 [英] Spring WebFlux: Serve files from controller

问题描述

来自.NET和Node，我真的很难弄清楚如何将该阻塞的MVC控制器转移到非阻塞的WebFlux注释的控制器?我已经理解了这些概念，但是没有找到合适的异步Java IO方法(我希望该方法可以返回Flux或Mono).

Coming from .NET and Node I really have a hard time to figure out how to transfer this blocking MVC controller to a non-blocking WebFlux annotated controller? I've understood the concepts, but fail to find the proper async Java IO method (which I would expect to return a Flux or Mono).

@RestController
@RequestMapping("/files")
public class FileController {

    @GetMapping("/{fileName}")
    public void getFile(@PathVariable String fileName, HttpServletResponse response) {
        try {
            File file = new File(fileName);
            InputStream in = new java.io.FileInputStream(file);
            FileCopyUtils.copy(in, response.getOutputStream());
            response.flushBuffer();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

推荐答案

首先，使用Spring MVC实现该目标的方法应如下所示:

First, the way to achieve that with Spring MVC should look more like this:

@RestController
@RequestMapping("/files")
public class FileController {

    @GetMapping("/{fileName}")
    public Resource getFile(@PathVariable String fileName) {
        Resource resource = new FileSystemResource(fileName);        
        return resource;
    }
}

此外，如果您只是在没有附加逻辑的情况下仅服务器这些资源，则可以使用Spring MVC的

Also, not that if you just server those resources without additional logic, you can use Spring MVC's static resource support. With Spring Boot, spring.resources.static-locations can help you customize the locations.

现在，使用Spring WebFlux，您还可以配置相同的spring.resources.static-locations配置属性以提供静态资源.

Now, with Spring WebFlux, you can also configure the same spring.resources.static-locations configuration property to serve static resources.

该WebFlux版本看起来完全一样.如果需要执行涉及某些I/O的逻辑，则可以直接返回Mono<Resource>而不是Resource，例如:

The WebFlux version of that looks exactly the same. If you need to perform some logic involving some I/O, you can return a Mono<Resource> instead of a Resource directly, like this:

@RestController
@RequestMapping("/files")
public class FileController {

    @GetMapping("/{fileName}")
    public Mono<Resource> getFile(@PathVariable String fileName) {
        return fileRepository.findByName(fileName)
                 .map(name -> new FileSystemResource(name));
    }
}

请注意，对于WebFlux，如果返回的Resource实际上是磁盘上的文件，我们将使用

Note that with WebFlux, if the returned Resource is actually a file on disk, we will leverage a zero-copy mechanism that will make things more efficient.

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