Transfer "complex" DTO via REST

I have to transfer a quite complex “data transfer object” (DTO) from an Android app via REST to a backend server. I use the Spring framework (Spring boot) which by default encodes the DTO via Jackson. However, the server never recognizes this object as a whole and assignes it or a subset of it to null.
1 answer

This one is the BEST answer!

I searched for another encoder and found Google’s “GSON” project. I used it to encode the DTO “manually” (without Spring) into a String, sent it to the server and decoded the string there again via GSON (without Spring) into the original object. This time it worked as expected.