Question: I have completely Clear Excel File. it has 5 MB size I can't find a problem. I have the same problem with a work-related file.

<https://ufile.io/xsvqd>

On the link, you can download the file.

Answer: 
You need to use ServerWebExchange.

```
@PostMapping(value = "webclient/rest6", consumes = {"application/x-www-form-urlencoded"})
public Mono<String> redirectComplete(ServerWebExchange exchange) {
    Mono<MultiValueMap<String, String>> data = exchange.getFormData();

    return data.map(formData -> {
        String parameterValue = formData.getFirst("id");
        ...
        return Mono.just("result data");
    });
}

```
Your *postWithFormData()* code is OK.

The problem is in your *rest4(..)* method. You can't use *@RequestParam* annotation in order to get POST parameter (it should be used to get GET parameters).

You can use DTO instead. If you change the code this way it should work:

```
  @PostMapping(value = "rest4")
  public ResponseEntity<String> rest4(ValueDto value) {
    System.out.println(value.getId());
    ResponseEntity<String> response = new ResponseEntity<String>("Success", HttpStatus.OK);
    return response;
  }

  static class ValueDto {
    private String id;

    public String getId() {
      return id;
    }

    public void setId(String id) {
      this.id = id;
    }
  }

```