In Chapter 7, Advanced Spring Boot Features, we discussed advanced Spring Boot features, such as externalized configuration, monitoring, embedded servers, and deploying to the Cloud. In this chapter, let's turn our attention to data. Where we store our data and how we store data has been in rapid evolution during the last decade. After a few decades of stability with relational databases, in the last decade, a number of unstructured, nonrelational databases are taking firm ground. With a variety of data stores in play, the frameworks that talk to these data stores are becoming more important. While JPA made it easy to talk to relational databases, Spring Data aims to bring in a common approach to talk to a wider variety of data stores--relational or otherwise.

The following are some of the questions we will answer during this chapter:

• What is Spring Data?
• What are the aims of Spring Data?
• How do you talk to a relational database using Spring Data and Spring Data JPA?
• How do you talk to a nonrelational database such as MongoDB using Spring Data?