Configuration and Setup

Hibernate configuration is where, in five lines of properties, you make decisions whose consequences you will pay for years. Two of them deserve a closer look: how the database schema is created, and how SQL queries are made visible.

The first decision is the schema. Hibernate can derive a CREATE TABLE from your entities, and that is extremely convenient during the first three days of a project. Most teams leave this setting in place, push it to production, and discover one morning that a column renamed in the code caused an empty column to appear in the database next to the old one, which is full of data. There is no going back: Hibernate does not know how to migrate data, only how to reconcile structures.

The second decision is visibility. An ORM produces SQL that you did not write; as long as that SQL is not in front of you, you can neither understand nor fix a performance problem. The running theme of this course, the N+1 queries, is literally invisible without logging enabled. That is why this lesson configures logging before everything else.

We cover both ways to bootstrap: the Jakarta EE persistence.xml, which remains the reference for understanding what is going on, and the Spring Boot configuration, which is what you will write in practice.