The Ultimate Guide to Spring Profiles for Environment-Specific Properties

Spring Profiles are a powerful feature in Spring Boot that allows developers to manage environment-specific configurations with ease. This blog dives deep into the concept of Spring Profiles, covering their configuration, activation, precedence, and practical examples.

What are Spring Profiles?

Spring Profiles provide a way to segregate parts of your application’s configuration and make it environment-specific. For example, you can have different configurations for development, testing, and production environments. By activating a profile, you can control which set of configurations is loaded at runtime.

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Configuring Spring Profiles

Spring Profiles are typically defined in property files. You can create different property files for each environment:

Default Configuration (application.properties):

spring.application.name=spring-profiles-example
# Default profile active if no profile is specified
spring.profiles.active=dev

Development Configuration (application-dev.properties):

app.message=This is the DEV environment.
server.port=8081

Production Configuration (application-prod.properties):

app.message=This is the PROD environment.
server.port=8082

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How Spring Boot Loads Properties

1. Default Property File: application.properties is always loaded.

2. Profile-Specific Property Files: If a profile is active (e.g., dev), Spring Boot will also load application-dev.properties.

3. Precedence: Properties in the profile-specific file override those in application.properties if they overlap.

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Activating Spring Profiles

Using application.properties:

You can activate a profile by setting the spring.profiles.active property in the application.properties file:

spring.profiles.active=dev

Using the java -jar Command:

When running your Spring Boot application as a JAR, you can activate a profile by passing it as an argument:

java -jar myapp.jar --spring.profiles.active=dev

Activating Multiple Profiles:

You can activate multiple profiles by specifying them as a comma-separated list:

java -jar myapp.jar --spring.profiles.active=dev,prod

Spring Boot will load properties from all specified profiles, with the last profile taking precedence in case of overlapping properties.

Using Environment Variables:

You can set the active profile via environment variables, which is useful for deployments:

export SPRING_PROFILES_ACTIVE=prod
java -jar myapp.jar

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Example: Counting Digits in an Integer Without Strings

To illustrate Spring Profiles in action, consider a utility function that counts the number of digits in an integer without using string conversion. This functionality could be environment-specific, such as logging differently in development and production.

Utility Function:

public static int getSize(int number) {
    if (number == 0) {
        return 1;
    }
    number = Math.abs(number);
    return (int) Math.log10(number) + 1;
}

This function uses mathematical operations to determine the size of an integer, ignoring any negative signs.

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Example Application

Here’s a simple Spring Boot application that demonstrates how to use Spring Profiles to manage environment-specific configurations:

Main Application:

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

Controller:

@RestController
class MessageController {

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

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

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Behavior Based on Profile Activation

Development Profile (dev):

• URL: http://localhost:8081/message

• Response: This is the DEV environment.

Production Profile (prod):

• URL: http://localhost:8082/message

• Response: This is the PROD environment.

No Profile Active:

• If no profile is specified and spring.profiles.active is not set, Spring Boot will rely solely on application.properties.

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Precedence of Properties

When multiple profiles are active, Spring Boot loads properties in the order specified in spring.profiles.active. Properties from the last profile listed take precedence.

Example:

If you activate dev,prod:

• application.properties is loaded first.

• application-dev.properties is loaded next.

• application-prod.properties is loaded last and overrides conflicting properties.

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Conclusion

Spring Profiles provide a robust way to manage environment-specific configurations in a Spring Boot application. By understanding how profiles are configured, activated, and prioritized, you can create flexible and maintainable applications that adapt seamlessly to different environments. Whether you’re deploying locally or in the cloud, Spring Profiles simplify the process of managing configurations for development, testing, and production environments.