Profile-based configuration in Spring Boot

Introduction

Profile-based configuration helps you run your app with different settings for different situations, like development or production. It keeps your app flexible and easy to manage.

When you want different database settings for testing and live use.

When you need to enable debug logging only during development.

When deploying the same app to multiple environments with different URLs or keys.

When you want to turn features on or off depending on the environment.

Syntax

Spring Boot

spring.profiles.active=profileName

# Example: application-dev.properties
server.port=8081

# Example: application-prod.properties
server.port=80

Use spring.profiles.active in application.properties or as a command line argument to select the active profile.

Create separate application-{profile}.properties files for each profile's settings.

Examples

This sets the active profile to dev. Spring Boot will load application-dev.properties settings.

Spring Boot

# application.properties
spring.profiles.active=dev

Settings used only when the dev profile is active.

Spring Boot

# application-dev.properties
server.port=8081
logging.level.root=DEBUG

Settings used only when the prod profile is active.

Spring Boot

# application-prod.properties
server.port=80
logging.level.root=ERROR

Run the app with the prod profile from the command line.

Spring Boot

# Command line
java -jar app.jar --spring.profiles.active=prod

Sample Program

This Spring Boot app reads a message from configuration based on the active profile and shows it at the home URL.

Create two files:

• application-dev.properties with app.message=Hello from Development!
• application-prod.properties with app.message=Welcome to Production!

Set the active profile to dev or prod to see different messages.

Spring Boot

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

@RestController
class HelloController {

    @Value("${app.message}")
    private String message;

    @GetMapping("/")
    public String home() {
        return message;
    }
}

Important Notes

You can activate multiple profiles by separating them with commas, like spring.profiles.active=dev,debug.

Profiles help keep sensitive info like passwords out of your main config.

Use @Profile annotation on beans to load them only for certain profiles.

Summary

Profiles let you switch app settings easily for different environments.

Create separate config files named application-{profile}.properties.

Activate profiles via properties file, command line, or environment variables.

Practice

1. What is the main purpose of using profiles in Spring Boot configuration?

easy

A. To switch application settings easily for different environments

B. To write Java code faster

C. To create user interfaces

D. To manage database connections manually

Solution

1. Step 1: Understand what profiles do

   Profiles allow you to have different settings for different environments like development, testing, and production.

2. Step 2: Identify the main use

   Switching settings easily means you can run the same app with different configurations without changing code.

3. Final Answer:

   To switch application settings easily for different environments -> Option A

4. Quick Check:

   Profiles = environment-specific settings [OK]

Hint: Profiles = different settings for different environments [OK]

Common Mistakes:

• Thinking profiles are for writing code
• Confusing profiles with UI design
• Believing profiles manage database manually

2. Which of the following is the correct way to name a Spring Boot properties file for a profile named dev?

easy

A. application-dev.properties

B. application.properties-dev

C. dev-application.properties

D. application_dev.properties

Solution

1. Step 1: Recall Spring Boot profile file naming

   Spring Boot expects profile-specific files named as application-{profile}.properties.

2. Step 2: Match the correct pattern

   For profile 'dev', the file should be application-dev.properties.

3. Final Answer:

   application-dev.properties -> Option A

4. Quick Check:

   Profile file = application-{profile}.properties [OK]

Hint: Profile files use dash between application and profile [OK]

Common Mistakes:

• Using underscore instead of dash
• Placing profile after .properties
• Starting filename with profile name

3. Given these files:
application.properties contains server.port=8080
application-prod.properties contains server.port=9090
And the active profile is set to prod, what port will the Spring Boot app run on?

medium

A. 8080

B. 9090

C. Both 8080 and 9090

D. No port will be set

Solution

1. Step 1: Understand profile override behavior

   Properties in profile-specific files override those in the default application.properties when the profile is active.

2. Step 2: Apply active profile 'prod'

   Since 'prod' is active, server.port=9090 from application-prod.properties overrides 8080.

3. Final Answer:

   9090 -> Option B

4. Quick Check:

   Active profile properties override default [OK]

Hint: Active profile settings override defaults [OK]

Common Mistakes:

• Assuming default always applies
• Thinking both ports run simultaneously
• Ignoring profile activation

4. You wrote spring.profiles.active=dev in application.properties, but your app still uses default settings. What is the likely problem?

medium

A. The dev profile is not supported by Spring Boot

B. You need to restart the app after changing profiles

C. The profile-specific file is named application_dev.properties instead of application-dev.properties

D. Profiles cannot be set in application.properties

Solution

1. Step 1: Check profile file naming

   Spring Boot requires profile files named with dash, not underscore.

2. Step 2: Identify mismatch

   If the file is named application_dev.properties, Spring Boot won't recognize it for profile 'dev'.

3. Final Answer:

   Incorrect profile file naming with underscore -> Option C

4. Quick Check:

   Profile file must use dash, not underscore [OK]

Hint: Use dash, not underscore, in profile filenames [OK]

Common Mistakes:

• Thinking profiles can't be set in application.properties
• Forgetting to restart app (usually needed but not main issue here)
• Believing 'dev' profile is unsupported

5. You want to activate the test profile without changing application.properties. Which of these is a valid way to do it when running your Spring Boot app from the command line?

hard

A. java -jar app.jar -profile test

B. java -jar app.jar -Dspring.profiles.active=test

C. java -jar app.jar --profile=test

D. java -jar app.jar --spring.profiles.active=test

Solution

1. Step 1: Recall command line profile activation syntax

   Spring Boot uses --spring.profiles.active=profile to activate profiles via command line arguments.

2. Step 2: Check each option

   java -jar app.jar --spring.profiles.active=test uses the correct Spring Boot command-line syntax. java -jar app.jar -Dspring.profiles.active=test incorrectly places the -D JVM argument after -jar; correct would be java -Dspring.profiles.active=test -jar app.jar. Flags like -profile test and --profile=test are not supported by Spring Boot.

3. Final Answer:

   java -jar app.jar --spring.profiles.active=test -> Option D

4. Quick Check:

   Use --spring.profiles.active=profile on command line [OK]

Hint: Use --spring.profiles.active=profile to activate profiles [OK]

Common Mistakes:

• Using -profile or --profile flags incorrectly
• Confusing JVM -D options without proper placement
• Trying to set profile inside application.properties only