79. Database Initialization

An SQL database can be initialized in different ways depending on what your stack is. Of course, you can also do it manually, provided the database is a separate process.

79.1 Initialize a Database Using JPA

JPA has features for DDL generation, and these can be set up to run on startup against the database. This is controlled through two external properties:

  • spring.jpa.generate-ddl (boolean) switches the feature on and off and is vendor independent.
  • spring.jpa.hibernate.ddl-auto (enum) is a Hibernate feature that controls the behavior in a more fine-grained way. This feature is described in more detail later in the document.

79.2 Initialize a Database Using Hibernate

You can set spring.jpa.hibernate.ddl-auto explicitly and the standard Hibernate property values are none, validate, update, create, and create-drop. Spring Boot chooses a default value for you based on whether it thinks your database is embedded. It defaults to create-drop if no schema manager has been detected or none in all other cases. An embedded database is detected by looking at the Connection type. hsqldb, h2, and derby are embedded, and others are not. Be careful when switching from in-memory to a ‘real’ database that you do not make assumptions about the existence of the tables and data in the new platform. You either have to set ddl-auto explicitly or use one of the other mechanisms to initialize the database.


You can output the schema creation by enabling the org.hibernate.SQL logger. This is done for you automatically if you enable the debug mode.

In addition, a file named import.sql in the root of the classpath is executed on startup if Hibernate creates the schema from scratch (that is, if the ddl-auto property is set to create or create-drop). This can be useful for demos and for testing if you are careful but is probably not something you want to be on the classpath in production. It is a Hibernate feature (and has nothing to do with Spring).

79.3 Initialize a Database

Spring Boot can automatically create the schema (DDL scripts) of your DataSource and initialize it (DML scripts). It loads SQL from the standard root classpath locations: schema.sql and data.sql, respectively. In addition, Spring Boot processes the schema-${platform}.sql and data-${platform}.sql files (if present), where platform is the value of spring.datasource.platform. This allows you to switch to database-specific scripts if necessary. For example, you might choose to set it to the vendor name of the database (hsqldb, h2, oracle, mysql, postgresql, and so on).

Spring Boot automatically creates the schema of an embedded DataSource. This behavior can be customized by using the spring.datasource.initialization-mode property (and it can also be always or never).

By default, Spring Boot enables the fail-fast feature of the Spring JDBC initializer, so, if the scripts cause exceptions, the application fails to start. You can tune that behavior by setting spring.datasource.continue-on-error.


In a JPA-based app, you can choose to let Hibernate create the schema or use schema.sql, but you cannot do both. Make sure to disable spring.jpa.hibernate.ddl-auto if you use schema.sql.

79.4 Initialize a Spring Batch Database

If you use Spring Batch, it comes pre-packaged with SQL initialization scripts for most popular database platforms. Spring Boot can detect your database type and execute those scripts on startup. If you use an embedded database, this happens by default. You can also enable it for any database type, as shown in the following example:


You can also switch off the initialization explicitly by setting spring.batch.initialize-schema=never.

79.5 Use a Higher-level Database Migration Tool

Spring Boot supports two higher-level migration tools: Flyway and Liquibase.

79.5.1 Execute Flyway Database Migrations on Startup

To automatically run Flyway database migrations on startup, add the org.flywaydb:flyway-core to your classpath.

The migrations are scripts in the form V<VERSION>__<NAME>.sql (with <VERSION> an underscore-separated version, such as ‘1’ or ‘2_1’). By default, they live in a folder called classpath:db/migration, but you can modify that location by setting spring.flyway.locations. You can also add a special {vendor} placeholder to use vendor-specific scripts. Assume the following:


Rather than using db/migration, the preceding configuration sets the folder to use according to the type of the database (such as db/migration/mysql for MySQL). The list of supported database are available in DatabaseDriver.

See the Flyway class from flyway-core for details of available settings such as schemas and others. In addition, Spring Boot provides a small set of properties (in FlywayProperties) that can be used to disable the migrations or switch off the location checking. Spring Boot calls Flyway.migrate() to perform the database migration. If you would like more control, provide a @Bean that implements FlywayMigrationStrategy.

Flyway supports SQL and Java callbacks. To use SQL-based callbacks, place the callback scripts in the classpath:db/migration folder. To use Java-based callbacks, create one or more beans that implement FlywayCallback or, preferably, extend BaseFlywayCallback. Any such beans are automatically registered with Flyway. They can be ordered by using @Order or by implementing Ordered.

By default, Flyway autowires the (@Primary) DataSource in your context and uses that for migrations. If you like to use a different DataSource, you can create one and mark its @Bean as @FlywayDataSource. If you do so and want two data sources, remember to create another one and mark it as @Primary. Alternatively, you can use Flyway’s native DataSource by setting spring.flyway.[url,user,password] in external properties.

There is a Flyway sample so that you can see how to set things up.

You can also use Flyway to provide data for specific scenarios. For example, you can place test-specific migrations in src/test/resources and they are run only when your application starts for testing. If you want to be more sophisticated, you can use profile-specific configuration to customize spring.flyway.locations so that certain migrations run only when a particular profile is active. For example, in application-dev.properties, you might specify the following setting:


With that setup, migrations in dev/db/migration run only when the dev profile is active.

79.5.2 Execute Liquibase Database Migrations on Startup

To automatically run Liquibase database migrations on startup, add the org.liquibase:liquibase-core to your classpath.

By default, the master change log is read from db/changelog/db.changelog-master.yaml, but you can change the location by setting spring.liquibase.change-log. In addition to YAML, Liquibase also supports JSON, XML, and SQL change log formats.

By default, Liquibase autowires the (@Primary) DataSource in your context and uses that for migrations. If you like to use a different DataSource, you can create one and mark its @Bean as @LiquibaseDataSource. If you do so and you want two data sources, remember to create another one and mark it as @Primary. Alternatively, you can use Liquibase’s native DataSource by setting spring.liquibase.[url,user,password] in external properties.

See LiquibaseProperties for details about available settings such as contexts, the default schema, and others.

There is a Liquibase sample so that you can see how to set things up.