There is an increasing demand for modern software systems to deliver continuous services with dynamic updates of no restart. Dynamic software update (DSU) aims to achieve this goal by patching the systems on the fly, but is currently hindered from practice due to non-trivial cross-version object state transformations. This paper revisits this problem by an in-depth empirical study over 190 class changes from Tomcat 8. The study produced an important finding that most transformers for non-trivial state transformations can be constructed by reassembling existing old/new version code. Based on this finding, this paper presents a domain-specific language and a synthesis algorithm with dedicated optimizations for the searching efficiency, to automatically synthesize non-trivial object transformers. We experimentally evaluated our tool implementation PASTA with real-world software systems, reporting PASTA’s effectiveness in succeeding in 7.5X non-trivial object transformation tasks as compared with the best existing DSU techniques.