It depends on how willing you are to allow your object graph to match your relational schema. The key is to let SQL be SQL. I wrote one that allows you to load data using standard SQL resource files, but it handles the persistence automatically:

https://github.com/bgard6977/sqorm

Flyway & jOOq take a similar approach:

https://www.jooq.org/

Taking the SQL-first approach also allows you to serialize without circular reference problems, since you don't just load the data, you also define a path to decompose the graph into a DAG.