What experience do I need to get started with Across?

You need a good grasp of Java (8) and Spring Framework. Spring MVC experience is strongly advised, and some Spring Boot knowledge might be helpful.

At the very least you should be familiar with Spring’s approach for dependency injection, the ApplicationContext and java-based configuration.

Other commonly used libraries that are useful to know are Hibernate, Spring Data, Liquibase and Thymeleaf.