livelessons-bootstrap-autoconfiguration

Lesson 1: Bootstrapping (Understanding Auto-configuration)

Introduction

This example shows how Spring Boot auto-configuration works.

Building and running the sample

Use the following commands to build run the application:

$ mvn clean package
$ mvn spring-boot:run

About the code

This example adds auto-configuration to show how the process generally works. The src/main/resources/META-ING/spring.factories contains a single entry which points to LogTomcatVersionAutoConfiguration. This class simply logs the current version of Tomcat.

There are a couple of @Conditions on LogTomcatVersionAutoConfiguration which affect when it is used. The @ConditionalOnClass annotation makes sure that Tomcat has been declared as a dependency. The @ConditionalOnProperty annotation shows how you can check that a property has a specific value.

You can change the application.properties file or the pom.xml file if you want to test the conditions.