Spring Boot Auto-Configuration and Starters 5

Question 1

Which @ConditionalOn* annotation checks that NO bean of the specified type is already registered before creating a new one?

Accepted Answer

@ConditionalOnMissingBean

Answer

@ConditionalOnMissingBean activates configuration only when no bean of the given type or name is already present in the ApplicationContext.

Question 2

You want your auto-configuration to activate only when exactly one candidate bean of a given type exists. Which annotation enforces this?

Accepted Answer

@ConditionalOnSingleCandidate

Answer

@ConditionalOnSingleCandidate matches when exactly one bean of the specified type is registered, or one is marked @Primary among multiple.

Question 3

Which property controls whether Spring Boot's auto-configured Jackson ObjectMapper serializes null values?

Accepted Answer

spring.jackson.default-property-inclusion=non_null

Answer

Setting spring.jackson.default-property-inclusion=non_null tells the auto-configured ObjectMapper to omit null fields from JSON output.

Question 4

What does adding spring-boot-devtools to a Spring Boot project do during development?

Accepted Answer

It provides automatic application restart and LiveReload on classpath changes

Answer

spring-boot-devtools watches the classpath and triggers automatic restarts and LiveReload browser refreshes when files change.

Question 5

Which condition checks for the existence of a specific file or classpath resource before applying auto-configuration?

Accepted Answer

@ConditionalOnResource

Answer

@ConditionalOnResource applies configuration only when a specified resource path (file: or classpath:) exists.

Spring Boot Practice Test