What is Auto-Configuration in Spring Boot and how does it work internally? स्प्रिंग बूट में ऑटो-कॉन्फिगरेशन क्या है और यह आंतरिक रूप से कैसे काम करता है?

Auto-Configuration automatically configures Spring beans based on the JAR dependencies present on the classpath, existing beans, and property values, removing the need for explicit XML or Java configuration for common setups.

It is triggered by @EnableAutoConfiguration, included inside @SpringBootApplication. Spring Boot scans classes listed in META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports, and each auto-configuration class is guarded by conditional annotations such as @ConditionalOnClass, @ConditionalOnMissingBean, and @ConditionalOnProperty so it only applies when appropriate.

@Configuration
@ConditionalOnClass(DataSource.class)
@ConditionalOnMissingBean(DataSource.class)
public class DataSourceAutoConfiguration {
    // auto-configured bean definitions
}