How SpringBoot AutoConfiguration magic works?

Spring Boot's AutoConfiguration relies on Spring's @Conditional feature to register beans conditionally based on arbitrary criteria such as classpath presence, existing beans, property values, or system properties. The @EnableAutoConfiguration annotation triggers classpath scanning and loads AutoConfiguration classes from spring-boot-autoconfigure.jar. These classes use annotations like @ConditionalOnClass, @ConditionalOnMissingBean, and @ConditionalOnProperty to decide which beans to register. A detailed walkthrough of DataSourceAutoConfiguration illustrates how Spring Boot automatically configures a DataSource based on available classes and application.properties settings, with custom Condition implementations shown step by step.