@SuppressWarnings("NullableProblems")
        @Override
        public HttpHeaders getHeaders() {
            long contentLength = headers.getContentLength();
            if (contentLength == 0) {
                headers.set(HttpHeaders.TRANSFER_ENCODING, "chunked");
            }
            return headers;
        }
To linked multiValue map.

@param json the json
@return the linked multiValue map
shenyu-plugin/shenyu-plugin-param-mapping/src/main/java/org/apache/shenyu/plugin/param/mapping/strategy/FormDataOperator.java