@Value for property injection in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

The @Value annotation is used to inject values from property files or environment variables directly into Spring-managed beans.

beginner

How do you inject a property named app.name from application.properties using @Value?

You use @Value("${app.name}") on a field or setter method to inject the value of app.name from the properties file.

intermediate

Can @Value inject default values if the property is missing? How?

Yes. You can provide a default value using the syntax @Value("${property.name:defaultValue}"). If property.name is missing, defaultValue is used.

beginner

Where can @Value be applied in a Spring bean?

@Value can be applied on fields, constructor parameters, or setter methods to inject property values.

intermediate

What happens if you use @Value with a property that does not exist and no default value is provided?

Spring will throw an exception during application startup because it cannot resolve the property value.

Which syntax correctly injects the property server.port using @Value?

A @Value("#server.port")

B @Value("server.port")

C @Value(server.port)

D @Value("${server.port}")

The correct syntax uses ${property.name} inside quotes to inject the property value.

How do you provide a default value of 8080 for server.port if it is missing?

A @Value("${server.port:8080}")

B @Value("${server.port?8080}")

C @Value("${server.port|8080}")

D @Value("${server.port=8080}")

The colon : syntax inside ${} provides a default value.

Where can you NOT use @Value in a Spring bean?

A On local variables inside methods

B On constructor parameters

C On setter methods

D On private fields

@Value cannot be used on local variables inside methods because Spring injects values during bean creation.

What will happen if a property used in @Value is missing and no default is set?

A Spring uses null as the value

B Spring ignores the missing property

C Spring throws an exception at startup

D Spring logs a warning but continues

Spring fails to start because it cannot resolve the required property.

Which of these is a valid example of injecting a property with @Value?

A @Value("my.property") private String prop;

B @Value("${my.property}") private String prop;

C @Value(my.property) private String prop;

D @Value(#my.property) private String prop;

Only option C uses the correct syntax with ${} and quotes.

Explain how to use @Value to inject a property from application.properties into a Spring bean field.

Think about how Spring reads properties and injects them.

Describe what happens if a property referenced by @Value is missing and no default value is provided.

Consider Spring's behavior when required config is missing.