@ConfigurationProperties for type-safe config in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @ConfigurationProperties annotation in Spring Boot?

It binds external configuration properties (like those in application.properties or application.yml) to a Java class, enabling type-safe access to configuration values.

intermediate

How do you enable @ConfigurationProperties support in a Spring Boot application?

You add <code>@EnableConfigurationProperties</code> on a configuration class or use <code>@Component</code> on the properties class itself to register it as a Spring bean.

intermediate

What is the benefit of using @ConfigurationProperties over @Value annotations?

@ConfigurationProperties supports grouping related properties into a single class, supports complex types, and provides type safety and easier testing compared to scattered @Value injections.

beginner

How do you define a prefix for properties in a @ConfigurationProperties class?

You specify the prefix in the annotation like <code>@ConfigurationProperties(prefix = "app.settings")</code>. This means properties starting with <code>app.settings.</code> will be mapped to the class fields.

advanced

What must you do to ensure that a <code>@ConfigurationProperties</code> class is immutable?

Use constructor binding by adding <code>@ConstructorBinding</code> and define final fields with a constructor. This makes the configuration class immutable and thread-safe.

Which annotation is used to bind external properties to a Java class in Spring Boot?

A @Value

B @ConfigurationProperties

C @Autowired

D @ComponentScan

@ConfigurationProperties binds external config properties to a class.

How do you specify the prefix for properties in a @ConfigurationProperties class?

A Using <code>@ConfigurationProperties(prefix = "...")</code>

B Using <code>@Value(prefix = "...")</code>

C Using <code>@Component(prefix = "...")</code>

D Using <code>@EnableConfigurationProperties(prefix = "...")</code>

The prefix is set in @ConfigurationProperties(prefix = "...").

What annotation enables constructor binding for immutable configuration classes?

A @FinalBinding

B @ImmutableBinding

C @ConstructorBinding

D @ConfigBinding

@ConstructorBinding enables immutable config classes with constructor injection.

Which of these is NOT a benefit of using @ConfigurationProperties?

A Grouping related properties

B Type safety

C Supports complex nested properties

D Automatically reloads properties at runtime

@ConfigurationProperties does not automatically reload properties at runtime.

To register a @ConfigurationProperties class as a Spring bean, you can:

A Both A and B

B Add <code>@EnableConfigurationProperties</code> on a config class

C Neither A nor B

D Add <code>@Component</code> on the class

Both adding @Component or using @EnableConfigurationProperties registers the class.

Explain how @ConfigurationProperties helps in managing application configuration in Spring Boot.

Think about how you can organize and access config values easily.

Describe the steps to create an immutable configuration class using @ConfigurationProperties.

Focus on annotations and class design for immutability.