Another idea from the JVM Summit, because the JDK9 now uses fast string concatenation by default, a JSON serializer based on reflection can be outperformed by a hand written code. The following code is a small JSON serializer that use the StringConcatFactory of JDK9 https://gist.github.com/forax/76124b69631475105f87ddd2205a4d91 enjoy, Rémi