How to read a Multipart file as a string in Spring?

Question

I want to post a text file from my desktop using Advanced Rest Client. This is my controller:

@RequestMapping(value = "/vsp/debug/compareConfig/{deviceIp:.*}", method = RequestMethod.POST, consumes = { "multipart/form-data" }, produces = { "application/json" })  public ResponseEntity<SuccessResult> compareCLIs(HttpServletRequest request, @RequestParam("file") MultipartFile file, @PathVariable("deviceIp") String device)  { log.info(file.getOriginalFilename()); byte[] bytearr = file.getBytes(); log.info("byte length: ", bytearr.length); log.info("Size : ", file.getSize());  } 

This does not return any value for byte length or file size. I want to read the file values to a StringBuffer. Can someone provide pointers regarding this? I am not sure if I need to save this file before parsing it to a string. If so how do I save the file in the workspace?

Answer 1

If you want to load the content of a Multipart file into a String, the easiest solution is:

String content = new String(file.getBytes()); 

Or, if you want to specify the charset:

String content = new String(file.getBytes(), StandardCharsets.UTF_8); 

However, if your file is huge, this solution is maybe not the best.

Answer 2

First, this is not related to Spring, and, second, you don't need to save the file to parse it.

To read the content of a Multipart file into a String you can use Apache Commons IOUtils class like this

ByteArrayInputStream stream = new   ByteArrayInputStream(file.getBytes()); String myString = IOUtils.toString(stream, "UTF-8");