Skip to content
Deadline to Die

Module 3: Application Properties & Profiles (The Settings)

📚 Module 3: Application Properties & Profiles

Focus: Moving from “Hardcoded” to “Configurable.”

A professional app needs to run in different places. It runs on Your Laptop, on a Test Server, and in the Cloud. You don’t want to change your code every time you move it. We use Properties and Profiles.

🏗️ Step 1: The application.properties File

This is the “Control Panel” of your app.

🧩 The Analogy: The Oven Settings

Instead of building a separate oven for “Pizza” and “Cake,” you have one oven with a Dial.

  • You change the dial to 400°F for Pizza.
  • You change the dial to 325°F for Cake.

In Spring Boot: We use application.properties (or application.yml):

server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/mydb

🏗️ Step 2: Profiles (The “Environment Switch”)

Sometimes you need completely different settings for different environments.

🧩 The Analogy: The Driving Mode

  • Sports Mode: Tight suspension, high fuel use (Production Server - High performance).
  • Eco Mode: Soft suspension, low fuel use (Your Laptop - Low resources).

In Code:

  • application-dev.properties (Eco Mode)
  • application-prod.properties (Sports Mode)

You switch between them with one command: spring.profiles.active=prod.

🏗️ Step 3: @Value (The “Bridge”)

How do we get those settings into our Java code? We use the @Value label.

@Component
public class MyService {
    @Value("${app.name}")
    private String appName; // This variable now contains the setting from the file!
}

🥅 Module 3 Review

  1. Properties: External settings files for your app.
  2. Profiles: Groups of settings for different environments (Dev, Test, Prod).
  3. @Value: Reading a single setting into your code.
  4. Separation: Keeping your secret passwords and server names OUT of your code.