An embedded database is useful during the development phase of a project because of its lightweight nature. Benefits include ease of configuration, quick startup time, testability, and the ability to rapidly evolve SQL during development.

If you want to expose an embedded database instance as a bean in a Spring ApplicationContext, use the embedded-database tag in the spring-jdbc namespace:

    <jdbc:embedded-database id="dataSource">
        <jdbc:script location="classpath:schema.sql"/>
        <jdbc:script location="classpath:test-data.sql"/>
    </jdbc:embedded-database>

The preceding configuration creates an embedded HSQL database populated with SQL from schema.sql and testdata.sql resources in the classpath. The database instance is made available to the Spring container as a bean of type javax.sql.DataSource. This bean can then be injected into data access objects as needed.

The EmbeddedDatabaseBuilder class provides a fluent API for constructing an embedded database programmatically. Use this when you need to create an embedded database instance in a standalone environment, such as a data access object unit test:

    EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
    EmbeddedDatabase db = builder.type(H2).script("schema.sql").script("test-data.sql").build();
    // do stuff against the db (EmbeddedDatabase extends javax.sql.DataSource)
    db.shutdown()

Spring JDBC embedded database support can be extended in two ways:

You are encouraged to contribute back extensions to the Spring community at jira.springframework.org.

Spring supports HSQL 1.0.0 to 2.0.0. HSQL is the default embedded database if no type is specified explicitly. To specify HSQL explicitly, set the type attribute of the embedded-database tag to HSQL. If you are using the builder API, call the type(EmbeddedDatabaseType) method with EmbeddedDatabaseType.HSQL.

Spring supports H2 1.8.0 to 2.0.0. To enable H2, set the type attribute of the embedded-database tag to H2. If you are using the builder API, call the type(EmbeddedDatabaseType) method with EmbeddedDatabaseType.H2.

Spring supports Apache Derby 10.5.1.1 to 10.6.0. To enable Derby, set the type attribute of the embedded-database tag to Derby. If using the builder API, call the type(EmbeddedDatabaseType) method with EmbeddedDatabaseType.Derby.

Embedded databases provide a lightweight way to test data access code. The following is a data access unit test template that uses an embedded database:

public class DataAccessUnitTestTemplate {
    private EmbeddedDatabase db;
    
    @Before
    public void setUp() {
        // creates a HSQL in-memory db populated from classpath:schema.sql and classpath:test-data.sql
        db = EmbeddedDatabaseBuilder.buildDefault();		
    }

    @Test
    public void testDataAccess() {
        JdbcTemplate template = new JdbcTemplate(db);
        template.query(...);
    }

    @After
    public void tearDown() {
        db.shutdown();
    }
}