@SuppressWarnings("NullableProblems")
        @Override
        public Flux<DataBuffer> getBody() {
            return cachedBodyOutputMessage.getBody();
        }
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