Spring Boot - Loading Initial Data

Question

I'm wondering what the best way to load initial database data before the application starts? What I'm looking for is something that will fill my H2 database with data.

For example, I have a domain model "User" I can access users by going to /users but initially there won't be any users in the database so I have to create them. Is there anyway to fill the database with data automatically?

At the moment I have a Bean that gets instantiated by the container and creates users for me.

Example:

@Component
public class DataLoader {

    private UserRepository userRepository;

    @Autowired
    public DataLoader(UserRepository userRepository) {
        this.userRepository = userRepository;
        LoadUsers();
    }

    private void LoadUsers() {
        userRepository.save(new User("lala", "lala", "lala"));
    }
}

But I very much doubt that is the best way of doing it. Or is it?

Answer 1

You can simply create a data.sql file in your src/main/resources folder and it will be automatically executed on startup. In this file you just add some insert statements, eg.:

INSERT INTO users (username, firstname, lastname) VALUES
  ('lala', 'lala', 'lala'),
  ('lolo', 'lolo', 'lolo');

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Similarly, you can create a schema.sql file (or schema-h2.sql) as well to create your schema:

CREATE TABLE task (
  id          INTEGER PRIMARY KEY,
  description VARCHAR(64) NOT NULL,
  completed   BIT NOT NULL);

Though normally you shouldn't have to do this since Spring boot already configures Hibernate to create your schema based on your entities for an in memory database. If you really want to use schema.sql you'll have to disable this feature by adding this to your application.properties:

spring.jpa.hibernate.ddl-auto=none

More information can be found at the documentation about Database initialization.

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If you're using Spring boot 2, database initialization only works for embedded databases (H2, HSQLDB, ...). If you want to use it for other databases as well, you need to change the spring.datasource.initialization-mode property:

spring.datasource.initialization-mode=always

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If you're using multiple database vendors, you can name your file data-h2.sql or data-mysql.sql depending on which database platform you want to use.

To make that work, you'll have to configure the spring.datasource.platform property though:

spring.datasource.platform=h2