Profile-based configuration in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Spring Boot Profile Activation Behavior

Given a Spring Boot application with application.properties and application-dev.properties files, and the active profile set to dev, what will be the value of the property app.message if application.properties has app.message=Hello from default and application-dev.properties has app.message=Hello from dev?

A Hello from default

B An error occurs because of conflicting properties

C Hello from dev

D The property <code>app.message</code> will be empty

💡 Hint

Spring Boot uses the active profile properties to override default properties.

When a profile is active, Spring Boot loads application.properties first, then overrides with application-{profile}.properties. So app.message from application-dev.properties replaces the default.

📝 Syntax

intermediate

Correct Syntax for Profile-Specific Bean Declaration

Which of the following is the correct way to declare a Spring bean that only loads when the test profile is active?

A

@Bean
@Profile({test})
public DataSource testDataSource() { return new DataSource(); }

B

@Bean
@Profile(test)
public DataSource testDataSource() { return new DataSource(); }

C

@Bean
@Profile('test')
public DataSource testDataSource() { return new DataSource(); }

D

@Bean
@Profile("test")
public DataSource testDataSource() { return new DataSource(); }

💡 Hint

Profile annotation requires a string value with double quotes.

The @Profile annotation requires the profile name as a string in double quotes. Option D uses the correct syntax.

🔧 Debug

advanced

Why Does the Profile-Specific Property Not Load?

A developer has application.properties and application-prod.properties. They set spring.profiles.active=prod in application.properties. But the properties from application-prod.properties are not loaded at runtime. What is the most likely cause?

A The <code>spring.profiles.active</code> property must be set as a command-line argument or environment variable, not inside <code>application.properties</code>.

B Spring Boot does not support multiple property files for profiles.

C The profile name <code>prod</code> is misspelled in the filename.

D Setting <code>spring.profiles.active</code> inside <code>application.properties</code> disables profile-specific loading.

💡 Hint

Active profiles set inside application.properties can cause loading order issues.

Setting spring.profiles.active inside application.properties can cause Spring Boot to load properties incorrectly because it reads application.properties before knowing the active profile. It is recommended to set active profiles via command-line or environment variables.

❓ state_output

advanced

Output of Bean Initialization with Multiple Active Profiles

Consider a Spring Boot app with two active profiles: dev and qa. There are two beans defined with @Profile("dev") and @Profile("qa") respectively. What happens when the app starts?

A Only the bean with <code>@Profile("dev")</code> loads because it is first in the list.

B Both beans load because both profiles are active.

C Neither bean loads because Spring Boot supports only one active profile at a time.

D An error occurs due to conflicting beans with different profiles.

💡 Hint

Spring Boot supports multiple active profiles simultaneously.

When multiple profiles are active, Spring Boot loads beans for all active profiles. So both beans annotated with @Profile("dev") and @Profile("qa") will be created.

🧠 Conceptual

expert

Understanding Profile-Specific Property Precedence

In Spring Boot, if you have application.properties, application-dev.properties, and application-local.properties, and you activate both dev and local profiles, which property file has the highest precedence when properties conflict?

A The last profile listed in <code>spring.profiles.active</code> has the highest precedence

B <code>application-dev.properties</code> because it is the first profile alphabetically

C <code>application.properties</code> because it is the base configuration

D <code>application-local.properties</code> because it is loaded last

💡 Hint

Order of profiles in spring.profiles.active affects property overriding.

When multiple profiles are active, Spring Boot loads application.properties first, then profile-specific files in the order they appear in spring.profiles.active. Later profiles override earlier ones.