public static <K, V> String toMap(final Supplier<MultiValueMap<K, V>> supplier) {
        return GsonUtils.getInstance().toJson(supplier.get().toSingleValueMap());
    }
map.

@param <K>      the type parameter
@param <V>      the type parameter
@param supplier supplier
@return String string
shenyu-plugin/shenyu-plugin-base/src/main/java/org/apache/shenyu/plugin/base/utils/HttpParamConverter.java