Custom auto-configuration in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is custom auto-configuration in Spring Boot?

Custom auto-configuration lets you create your own automatic setup for Spring Boot apps. It helps add features or settings without writing extra code each time.

beginner

Which annotation marks a class as an auto-configuration class in Spring Boot?

The <code>@Configuration</code> annotation marks the class as a configuration, and <code>@ConditionalOnClass</code> or other <code>@Conditional</code> annotations control when it applies.

intermediate

How does Spring Boot know to load your custom auto-configuration?

You list your auto-configuration class in a file named <code>META-INF/spring.factories</code> under the key <code>org.springframework.boot.autoconfigure.EnableAutoConfiguration</code>.

intermediate

What is the role of @ConditionalOnClass in custom auto-configuration?

It makes sure your auto-configuration runs only if a certain class is on the classpath, avoiding errors if dependencies are missing.

beginner

Why use custom auto-configuration instead of manual configuration?

It saves time by automating setup, reduces repeated code, and makes your app easier to maintain and extend.

What file must you create to register your custom auto-configuration in Spring Boot?

A application.properties

B pom.xml

C META-INF/spring.factories

D src/main/resources/config.yaml

Custom auto-configurations are registered in META-INF/spring.factories under the EnableAutoConfiguration key.

Which annotation helps your auto-configuration activate only when a specific class is present?

A @ConditionalOnClass

B @Component

C @EnableAutoConfiguration

D @ConditionalOnBean

@ConditionalOnClass checks if a class is on the classpath before applying the configuration.

What is the main benefit of custom auto-configuration?

A Writing XML configuration

B Manual setup of beans

C Disabling Spring Boot features

D Automatic setup of features

Custom auto-configuration automates feature setup, reducing manual work.

Which annotation is essential to mark a class as a configuration source in Spring Boot?

A @Component

B @Configuration

C @Service

D @Repository

@Configuration marks a class as a source of bean definitions.

Where do you place your custom auto-configuration class in a Spring Boot project?

A Under src/main/java with @Configuration

B In src/test/java

C In resources folder

D In META-INF folder

Auto-configuration classes are normal Java classes annotated with @Configuration placed in the main source folder.

Explain how to create and register a custom auto-configuration in Spring Boot.

Think about the steps from writing the class to telling Spring Boot about it.

Describe why conditional annotations are important in custom auto-configuration.

Consider what happens if a class your config needs is not present.