我找到了一个解决方案，即使我不知道它是否是最好的解决方案。

@PostMapping("/service")
    public ResponseEntity<byte[]> proxyPost(ProxyExchange<byte[]> proxy,
                                            @ModelAttribute ServiceDto serviceDto,
                                            @RequestHeader("authorization") String authorizationHeader,
                                            @RequestPart("file") MultipartFile file
                                           ) throws Exception {

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        proxy.headers(headers);
        proxy.body(this.buildBody(file,serviceDto));
        proxy.header("Authorization-getway",authorizationHeader);
        return proxy.uri(dzOptServiceUri + "/api/service/").post(response ->
             ResponseEntity.status(response.getStatusCode()) //
                    .headers(response.getHeaders()) //
                    .body(response.getBody())
        );
    }

    private MultiValueMap<String, Object> buildBody(MultipartFile file,ServiceDto serviceDto) throws IOException {
        MultiValueMap<String, Object> body = new LinkedMultiValueMap<>();
        body.add("libelle", serviceDto.getLibelle());
        body.add("definition", serviceDto.getDefinition());
        body.add("path", serviceDto.getPath());
        body.add("icone", serviceDto.getPath());

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);

        // Ajouter un fichier au corps de la requête
        body.add("file", new org.springframework.core.io.ByteArrayResource(file.getBytes()) {
            @Override
            public String getFilename() {
                return "";
            }
        });

        return body;
    }

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