How to Resolve 'Cannot Determine Embedded Database Driver Class for Database Type NONE' in Spring Boot?

What are the steps to resolve 'Cannot determine embedded database driver class for database type NONE' error when using Spring Boot with JPA?

@Configuration
@EnableJpaRepositories("demo.core.entity")
@EnableTransactionManagement
class JpaApplicationConfig {
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setPersistenceUnitName("transactions-optional");
        return factory;
    }
    @Bean
    public JpaTransactionManager transactionManager() {
        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory().getObject());
        return txManager;
    }
}

The error 'Cannot determine embedded database driver class for database type NONE' typically occurs in Spring Boot applications when the application is unable to auto-configure a data source for JPA. This can happen if the necessary database driver dependencies are missing or not configured correctly in your project.

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=

Causes

• Missing database driver dependencies in the project's build configuration (e.g., Maven or Gradle).
• Configuring Spring Data JPA without specifying a database (e.g., H2, MySQL) leads to Spring assuming there is no embedded database available.
• Your application might not have the correct dependency versions for DataNucleus and other libraries.

Solutions

• Add the appropriate database driver dependency in your POM.xml or build.gradle file, such as: ```xml <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <scope>runtime</scope> </dependency> ```
• Ensure your application.properties or application.yml file specifies the data source configuration. For example: ```properties spring.datasource.url=jdbc:h2:mem:testdb spring.datasource.driver-class-name=org.h2.Driver spring.datasource.username=sa spring.datasource.password= ```
• If you're using Google App Engine, ensure you have followed the correct setup for DataNucleus as per Google App Engine documentation.

Mistake: Not including the necessary database driver dependency.

Solution: Make sure to add the correct database driver to your Maven or Gradle dependencies.

Mistake: Configuring JPA without setting data source parameters in properties files.

Solution: Specify the datasource properties in your application.properties or application.yml.

Mistake: Using incorrect versions of dependencies that conflict with Spring Boot.

Solution: Check for compatibility between your Spring Boot version and other dependencies.