The H2 database is a popular database to use when developing Spring applications. H2 is written in Java and is easily runs as an embedded in-memory database. Because it is an embedded in memory database, it makes your build portable. Your build will run anywhere Maven will run.
If you used a database like Oracle or MySQL, now you’ve introduced an external dependency. Your build is no longer portable. If you wanted to do the build under Jekins on a build server, you’d need to install the database on that server or provide a configuration pointing to a database elsewhere.
By using the H2 database as an embedded in memory database, your build remains portable.
Configuring the H2 database with Spring Boot is very easy. You just need to add the H2 dependency to your Maven Pom. Spring Boot will automatically create the database, setup all the database JDBC objects, and by default configure Hibernate in a create-drop mode. Thus when Hibernate starts up, it will scan the JPA annotated classes and automatically generate and execute the SQL code needed to create the database tables.