Parsing MultipartFile data to string in spring

Question

I am trying to parse the MultipartFile data to string and return the string as response in java springboot. Can anyone suggest the right approach for this?

controller.java

@POST
@Path("/modelInfo")
@Produces({ "application/json" })
public Response getPretrainedModel(MultipartFile data) throws IOException {
    String content = new String(data.getBytes(), StandardCharsets.UTF_8);
    return Response.status(Response.Status.OK).entity(content).build();
}

file.json

{
  "documents": [
    {
      "id": "1",
      "text": "abc"
    }
  ]
}

I am sending file.json in request body as multipart/form-data and I want to read the content of the file and store it as string.

RUARO Thibault RUARO Thibault · Accepted Answer · 2020-08-04T10:04:36

If you are using Spring and Spring Boot, then you are not using the proper annotation. Spring does not support Jax-RS specification. Therefor, change your annotations for this one:

//    @POST
//    @Path("/modelInfo")
//    @Produces({ "application/json" })
@PostMapping(value = "/modelInfo", produces = MediaType.APPLICATION_JSON_VALUE)

Then, to return an object, you can just return the object in the method:

@PostMapping(value = "/modelInfo", produces = MediaType.APPLICATION_JSON_VALUE)
public String getPretrainedModel(@RequestParam("file") MultipartFile data) throws IOException {
    String content = new String(data.getBytes(), StandardCharsets.UTF_8);
    return content;
}

Note:

Don't forget to add the annotation @RequestParam in your method parameter to get the uploaded file. The name file must be the name of the attribute uploaded by your POST request
By default, the HTTP Response is 200 when you don't tell Spring to send something else.
If you want to override that, annotate your method with @ResponseStatus

Parsing MultipartFile data to string in spring

1 Answers