Auto-configuration is one of the most important features of Spring Boot. In this section, we will take a quick peek behind the scenes to understand how Spring Boot auto-configuration works.
Most of the Spring Boot auto-configuration magic comes from spring-boot-autoconfigure-{version}.jar. When we start any Spring Boot applications, a number of beans get auto-configured. How does this happen?
The following screenshot shows an extract from spring.factories from spring-boot-autoconfigure-{version}.jar. We have filtered out some of the configuration in the interest of space:
The preceding list of auto-configuration classes is run whenever a Spring Boot application is launched. Let's take a quick look at one of them:
org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration.
Here's a small snippet:
@Configuration
@ConditionalOnWebApplication...
