Configuration precedence order in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Spring Boot Configuration Precedence

In Spring Boot, multiple configuration sources can define the same property. Which source has the highest priority when resolving the value of a property?

A Command line arguments

B Environment variables

C application.properties file in src/main/resources

D Default properties set programmatically

💡 Hint

Think about how you might override a property quickly when running your app.

Spring Boot resolves properties by checking sources in a specific order. Command line arguments have the highest priority, allowing quick overrides without changing files.

❓ component_behavior

intermediate

Property Value Resolution in Spring Boot

Given the following property sources, which value will Spring Boot use for the property server.port when the application starts?

- application.properties file: server.port=8080
- Environment variable: SERVER_PORT=9090
- Command line argument: --server.port=7070

A 8080

B 7070

C 9090

D Default port 80

💡 Hint

Remember which source overrides others in Spring Boot.

Command line arguments override environment variables and property files, so 7070 is used.

📝 Syntax

advanced

Identifying Configuration Source Priority Error

Which of the following Spring Boot property source declarations will cause the application.properties file to be ignored, making environment variables take precedence?

A Setting <code>spring.config.location</code> to a non-existent directory

B Using <code>@PropertySource</code> annotation on a configuration class

C Placing <code>application.properties</code> in <code>src/main/resources</code>

D Setting <code>spring.config.name</code> to <code>application</code>

💡 Hint

Consider what happens if Spring Boot cannot find the config file location.

If spring.config.location points to a missing directory, Spring Boot skips loading application.properties from default locations, so environment variables take precedence.

❓ state_output

advanced

Resulting Property Value with Multiple Sources

Consider a Spring Boot app with these property sources:
- application.properties: app.mode=dev
- application-dev.properties: app.mode=development
- Environment variable: APP_MODE=production
- Command line argument: --app.mode=staging

If the app is started with the profile dev, what is the final value of app.mode?

A production

B development

C staging

D dev

💡 Hint

Profile-specific properties are overridden by command line arguments.

Command line arguments have the highest priority, so staging is the final value regardless of profile.

🔧 Debug

expert

Debugging Unexpected Property Value in Spring Boot

A developer sets spring.config.additional-location to a directory containing application.properties with feature.enabled=false. The default application.properties in src/main/resources has feature.enabled=true. The app always uses false for feature.enabled. Why?

Choose the correct explanation.

A Environment variables always override <code>spring.config.additional-location</code>.

B <code>spring.config.additional-location</code> properties are ignored if default <code>application.properties</code> exists.

C The property <code>feature.enabled</code> is case-sensitive and mismatched.

D <code>spring.config.additional-location</code> properties override default locations, so <code>false</code> is used.

💡 Hint

Check how additional locations affect property precedence.

Properties in spring.config.additional-location override those in default locations, so feature.enabled=false takes precedence.