In this chapter, we have covered several approaches to deal with relational database persistence. We first went through an example of integration between Scala and traditional JPA-based ORM persistence. The example also illustrated the integration between the Spring framework and a Scala codebase. We then introduced Anorm, the default persistence framework available in the Play Framework that relies on direct SQL queries. Because of some limitations of ORM, mainly related to scalability and performance, and limitations as well of plain SQL queries in terms of lack of type safety and lack of composability, we moved towards the adoption of the Slick framework, a unique approach to persistence that targets a more functional way to persist data in relational databases. Finally, we considered the case where we can generate a full Play web app with basic CRUD functionality out of an existing database as a way of rapidly getting started integrating Slick into Play. The future releases of Slick starting with 2.0 enhance support for code generation and strive for even more readable syntax for writing database queries through the usage of Scala macros.

In the next chapter, we are going to consider how to use Scala when integrating external systems together, in particular through Web Services and REST APIs, supporting data formats such as JSON and XML.