Should I reuse one instance of GSON or create new ones on demand?

Question

In most of my classes (especially server resources) I tend to create new instances of com.google.gson.Gson on demand. Sometimes I create them with the default constructor (for handling of simple POJOs), sometimes I use more sophisticated variants created with custom com.google.gson.GsonBuilder.

I know that Gson is a threadsafe class, so there is nothing standing against reusing the same instance of Gson instead of creating new ones. Heck, I might even reuse a static constant for this!

My question is this: should I create new instances whenever I need them, or should I create and use just one? What sort of performance implications will I be facing, if I serialize simple POJO with a Gson instance that was created with GsonBuilder and taught how to parse more complex data structures (had few custom serializers being registered)?

Answer 1

I know this is an old question but for future reference, the answer to this question is that you should go for the single instance if it is possible.

The creation of a GSON object is expensive depending on how many custom deserializer/serializer/handlers you register to it. I doubt that you will see any big performance boost from this.

About the second question, GSON internally has a list of registered serializer, and each one is checked against the object you are trying to parse. So you basically will add more iterations each time you register a custom serializer, but again, this is not a big performance issue compared to having a couple of big clumsy objects into memory.