How can i map domain object to several variant JSON objects (several DTO), without chain DOMAIN_OBJECT->DTO->JSON? I have one big domain object and more than ten variants of representation. When I map domain object to specific DTO with structMap and then do serialization to JSON with jackson I spend a lot of time.
Is there any tool for map domain object to serveral variants JSON without midle layer DTO ?
It really depends on what your more than ten variants are like. Sometimes, sticking to DTOs can be the best approach, as described in this answer, where DTOs are used define the contract of REST APIs.
Alternatively, depending on your needs, you could play with @JsonView from Jackson. Using Spring? This answer may give you some insights.
I don't really know your use case, but as a note, if you use Jackson I presume you are using ObjectMapper. The ObjectMapper is an expensive object which you should reuse as much as possible (ergo, declare it static and final), since it does a lot of caching behind the scene when the same object is converted lot of times.
Even better, get an ObjectWriter and/or ObjectReader from the ObjectMapper, which are immutable and thread-safe (ObjectMapper is tricky if you want to change its configuration at runtime), they should improve your performance.
Final thing, but I never went that far, you could write custom serializer / deserializer, but I see complexity going noticeably up (thus, it will be more difficult to mantain).
If you are working with strings, double check you use the StringBuilder (or StringBuffer on multi-threaded use case) and logging only when necessary (if(logger.isDebugEnabled() { log.debug(...) }), they are common pitfalls that bring performances down.
