Can Spring Boot set the name of a file being downloaded from a controller endpoint?-CodePudding

Java 11 and Spring Boot 2.5.x here. I understand that I can set up a controller to return the contents of a file like so:

@GetMapping(
  value = "/get-image-with-media-type",
  produces = MediaType.IMAGE_JPEG_VALUE
)
public @ResponseBody byte[] getImageWithMediaType() throws IOException {
    InputStream in = getClass()
      .getResourceAsStream("/path/to/some/image.jpg");
    return IOUtils.toByteArray(in);
}

But what if I want to control the name of the file that is sent back? For instance, on the server-side the file name might be stored as "image.jpg" but say I want to have it returned as "<userId>-<YYYY-mm-DD>-image.jpg", where <userId> is the user ID of the authenticated user making the request, and where <YYYY-mm-DD> is the date the request is made at?

For instance, if user 123 made the request on 12/10/2021, the file would be downloaded as "123-2021-12-10-image.jpg" and if user 234 made the request on 1/17/2022 it would be downloaded as "234-2022-01-17-image.jpg". Is this possible to control on the Spring/Java/server-side, or is it up to the HTTP client (browser, PostMan, whatever) to decide on the file name?

CodePudding user response：

Please try this, comments inline:

package com.example;

import java.io.IOException;
import java.security.Principal;
import java.util.Date;
import org.apache.commons.io.IOUtils;
import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;


@Controller
public class SomeController {

  @GetMapping(
      value = "/get-image-with-media-type",
      produces = MediaType.IMAGE_JPEG_VALUE
  ) // we can inject user like this (can be null, when not secured):
  public ResponseEntity<byte[]> getImageWithMediaType(Principal user) throws IOException {
    // XXXResource is the "spring way", FileSystem- alternatively: ClassPath-, ServletContext-, ...
    FileSystemResource fsr = new FileSystemResource("/path/to/some/image.jpg");
    HttpHeaders responseHeaders = new HttpHeaders();
    responseHeaders.set(HttpHeaders.CONTENT_DISPOSITION,
        // for direct downlad "inline", for "save as" dialog "attachment" (browser dependent)
        // filename placeholders: %1$s: user id string, 2$tY: year 4 digits, 2$tm: month 2 digits, %2$td day of month 2 digits
        String.format("inline; filename=\"%1$s-%2$tY-%2$tm-%2$td-image.jpg\"",
            // user name, current (server) date:
            user == null ? "anonymous" : user.getName(), new Date()));

    // and fire:
    return new ResponseEntity<>(
        IOUtils.toByteArray(fsr.getInputStream()),
        responseHeaders,
        HttpStatus.OK
    );
  }
}

Relevant reference:

Method Arguments(Principal)
Formatter
ResponseEntity( headers sample)
RFC2616 (Section 19.5.1 Content-Disposition)

With ContentDisposition it can look (just) like:

responseHeaders.setContentDisposition(
  ContentDisposition
    .inline()// or .attachment()
    .filename(// format file name:
      String.format(
        "%1$s-%2$tY-%2$tm-%2$td-image.jpg",
        user == null ? "anonymous" : user.getName(),
        new Date()
      )
    )
    .build()
);

TYVM: How to set 'Content-Disposition' and 'Filename' when using FileSystemResource to force a file download file?