Spring Boot auto-configuration
Spring Boot's ability to auto-configure the development environment so that developers can quickly integrate databases, Kafka queues, cloud services and AI models into their apps is one of the popular Java framework's biggest selling features. Few developers know how Spring Boot auto-configuration works, though.
Spring's @AutoConfiguration annotation
Spring Boot attempts to auto-configure any Java application that includes the @AutoConfiguration annotation. When Spring Boot encounters this annotation, it inspects the project and its dependencies to see which resources it might be able to auto-configure.
For example, if Spring Boot realizes the project being run uses a Java Database Connectivity database, such as PostgreSQL or SQL Server, it looks for a JavaBean capable of auto-configuring that database. If it finds a configuration bean, that component configures sensible defaults and looks for supplemental configuration information in the application.properties file.
Spring Boot auto-configuration occurs with minimal involvement from the programmer, so many developers assume that it's all black box magic. The truth is that all the code that supports Spring Boot's @AutoConfiguration annotation is open source and freely available.
Custom Spring auto-configuration classes
Furthermore, developers can easily create their own auto-configuration components in only a few lines of code. This is a great exercise if you want to understand how Spring Boot's @AutoConfiguration works.
To learn how to do exactly that, watch the video above. It helps you build a much better understanding of auto-configuration in Spring Boot.
Cameron McKenzie has been a Java EE software engineer for 20 years. His current specialties include Agile development; DevOps; Spring; and container-based technologies such as Docker, Swarm and Kubernetes.