Profile-based configuration in Spring Boot - Step-by-Step Execution

Concept Flow - Profile-based configuration

Start Application

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Check Active Profiles

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Load application.properties

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Load profile-specific properties

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Override common properties with profile ones

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Initialize Beans with final config

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Application runs with profile config

Spring Boot starts, checks which profile is active, loads common and profile-specific settings, then runs with the combined configuration.

Execution Sample

Spring Boot

spring.profiles.active=dev

# application.properties
app.name=MyApp

# application-dev.properties
app.name=MyApp-Dev

This example shows how Spring Boot loads common and dev profile properties, overriding app.name for dev.

Execution Table

Step	Action	Profile Active	Properties Loaded	Resulting app.name
1	Start application	none	application.properties	MyApp
2	Set active profile to dev	dev	application.properties + application-dev.properties	MyApp-Dev
3	Initialize beans with properties	dev	final combined properties	MyApp-Dev
4	Application runs	dev	final combined properties	MyApp-Dev

💡 Application runs with dev profile properties overriding common ones

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
spring.profiles.active	none	none	dev	dev
app.name	undefined	MyApp	MyApp-Dev	MyApp-Dev

Key Moments - 2 Insights

Why does app.name change after setting the active profile?

Because after Step 2, Spring Boot loads application-dev.properties which overrides app.name from the common application.properties, as shown in the execution_table rows 2 and 3.

What happens if no profile is active?

Only application.properties is loaded, so app.name stays as MyApp, as seen in Step 1 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of app.name after Step 1?

A MyApp-Dev

B undefined

C MyApp

D dev

💡 Hint

Check the 'Resulting app.name' column at Step 1 in the execution_table.

At which step does spring.profiles.active become 'dev'?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Profile Active' column in the execution_table and variable_tracker.

If we remove application-dev.properties, what would app.name be at Step 4?

A MyApp-Dev

B MyApp

C undefined

D dev

💡 Hint

Without profile-specific properties, only application.properties is loaded, as shown in Step 1.

Concept Snapshot

Spring Boot loads application.properties first.
If a profile is active, it loads application-{profile}.properties next.
Profile properties override common ones.
Use spring.profiles.active to set the profile.
This allows different configs for dev, test, prod environments.

Full Transcript

When Spring Boot starts, it first checks if any profile is active using spring.profiles.active. It loads the common application.properties file. If a profile like 'dev' is active, it also loads application-dev.properties. The profile-specific properties override the common ones. For example, app.name is 'MyApp' by default but becomes 'MyApp-Dev' when the dev profile is active. Beans initialize with the combined configuration. If no profile is active, only the common properties apply. This mechanism helps run the app with different settings for different environments easily.