1. Overview
Spring Boot makes it really easy to manage our database changes in an easy way. If we leave the default configuration, it’ll search for entities in our packages and create the respective tables automatically.
But sometimes we’ll need some finer grained control over the database alterations. That’s when we can use the data.sql and schema.sql files in Spring.
2. The data.sql File
Let’s also make the assumption here that we’re working with JPA – and define a simple Country entity in our project:
@Entity
public class Country {
@Id
@GeneratedValue(strategy = IDENTITY)
private Integer id;
@Column(nullable = false)
private String name;
//...
}
If we run our application, Spring Boot will create an empty table for us, but won’t populate it with anything.
An easy way to do this is to create a file named data.sql:
INSERT INTO country (name) VALUES ('India');
INSERT INTO country (name) VALUES ('Brazil');
INSERT INTO country (name) VALUES ('USA');
INSERT INTO country (name) VALUES ('Italy');
When we run the project with this file on the classpath, Spring will pick it up and use it for populating the database.
3. The schema.sql File
Sometimes, we don’t want to rely on the default schema creation mechanism. In such cases, we can create a custom schema.sql file:
CREATE TABLE country (
id INTEGER NOT NULL AUTO_INCREMENT,
name VARCHAR(128) NOT NULL,
PRIMARY KEY (id)
);
Spring will pick this file up and use it for creating a schema.
It’s also important to remember to turn off automatic schema creation to avoid conflicts:
spring.jpa.hibernate.ddl-auto=none
4. Conclusion
In this quick article, we saw how we can leverage schema.sql and data.sql files for setting up an initial schema and populating it with data.
Keep in mind that this approach is more suited for basic and simple scenarios, any advanced database handling would require more advanced and refined tooling like Liquibase or Flyway.
Code snippets, as always, can be found over on GitHub.