Download a File from Spring Boot Rest Service

download a file from Spring boot rest service

Option 1 using an InputStreamResource

Resource implementation for a given InputStream.

Should only be used if no other specific Resource implementation is > applicable. In particular, prefer ByteArrayResource or any of the file-based Resource implementations where possible.

@RequestMapping(path = "/download", method = RequestMethod.GET)
public ResponseEntity<Resource> download(String param) throws IOException {

    // ...

    InputStreamResource resource = new InputStreamResource(new FileInputStream(file));

    return ResponseEntity.ok()
            .headers(headers)
            .contentLength(file.length())
            .contentType(MediaType.APPLICATION_OCTET_STREAM)
            .body(resource);
}

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Option2 as the documentation of the InputStreamResource suggests - using a ByteArrayResource:

@RequestMapping(path = "/download", method = RequestMethod.GET)
public ResponseEntity<Resource> download(String param) throws IOException {

    // ...

    Path path = Paths.get(file.getAbsolutePath());
    ByteArrayResource resource = new ByteArrayResource(Files.readAllBytes(path));

    return ResponseEntity.ok()
            .headers(headers)
            .contentLength(file.length())
            .contentType(MediaType.APPLICATION_OCTET_STREAM)
            .body(resource);
}

How to download files from a third party Rest end point in Java

If you don't want to use additional dependecies other than jdk, you can use something like this:

URL url = new URL("http://localhost:8080/secure/attachment/1461863/fileName.txt");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");

    if (conn.getResponseCode() != 200) {
        throw new RuntimeException("Failed : HTTP error code : "
                + conn.getResponseCode());
    }

Downloading a file from spring controllers

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
    @PathVariable("file_name") String fileName, 
    HttpServletResponse response) {
    try {
      // get your file as InputStream
      InputStream is = ...;
      // copy it to response's OutputStream
      org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());
      response.flushBuffer();
    } catch (IOException ex) {
      log.info("Error writing file to output stream. Filename was '{}'", fileName, ex);
      throw new RuntimeException("IOError writing file to output stream");
    }

}

Generally speaking, when you have response.getOutputStream(), you can write anything there. You can pass this output stream as a place to put generated PDF to your generator. Also, if you know what file type you are sending, you can set

response.setContentType("application/pdf");

Downloading huge files from spring boot REST service

The code of the RestController is working as expected with a small memory footprint (the file is never loaded to the main memory completely).

The client code that works for me (also with a small memory footprint) can be found here.

Spring : Download file from REST controller

I modify the 'download' method with stream and it works correctly like I want.

public void download(Integer id, HttpServletResponse response){
    Line line = getById(Line.class, id);
    InputStream is = line.getFile().getBinaryStream;
    IOUtils.copy(is, response.getOutputStream());
    response.flushBuffer();
}

And my controller was like that :

public ResponseEntity<?> download(@RequestParam("id") Integer id, HttpServletResponse response)
{
    lineService.download(id,response);
    return new ResponseEntity<>(HttpStatus.OK);
}

Spring boot rest service to download a zip file which contains multiple file

Use these Spring MVC provided abstractions to avoid loading of whole file in memory.
org.springframework.core.io.Resource & org.springframework.core.io.InputStreamSource

This way, your underlying implementation can change without changing controller interface & also your downloads would be streamed byte by byte.

See accepted answer here which is basically using org.springframework.core.io.FileSystemResource to create a Resource and there is a logic to create zip file on the fly too.

That above answer has return type as void, while you should directly return a Resource or ResponseEntity<Resource> .

As demonstrated in this answer, loop around your actual files and put in zip stream. Have a look at produces and content-type headers.

Combine these two answers to get what you are trying to achieve.

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