JPA is huge! It covers nearly every aspect of communication between relational databases and the Java application and is deeply integrated into all major frameworks.
If you're using IntelliJ, JPA Buddy is super helpful. The plugin gently guides you through the subtleties of the most popular JPA implementations, visually reminds you of JPA features, generates code that follows best practices, and integrates intelligent inspections to improve your existing persistence code.
More concretely, it provides powerful tooling to generate Spring Data JPA repositories and methods, Flyway Versioned Migrations, Liquibase Differential Changelogs, DDL and SQL statements, DTO objects, and MapStruct interfaces.
Oh, and it actually generates JPA entities from an existing database and gradually update the data model as the database evolves! Yeah.