Auto Configuration in spring boot

Auto Configuration...

All auto configuration logic is executed in spring-boot-autoconfigure.jar. All auto configuration logic for MVC, JMS, data, and other frameworks is available in a JAR.

Auto-configuration @Conditional

If specific classes are offered in the classpath, then the configuration for that feature is enabled via auto configuration. Annotations such as @ConditionalOnMissingBean, @ConditionalOnClass, help in providing these functions.

Example 1

@Configuration

@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })

@EnableConfigurationProperties(DataSourceProperties.class)

@Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class })

public class DataSourceAutoConfiguration {

@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })

This configuration is enabled only when the classes are present in the classpath.