🌱 Spring Boot Interview Series – Q5 💡: Server Ports, HTTPS, Profiles & Hidden Tricks 🚀🔐🛠️

🌐 Changing the Default Server Port

By default, Spring Boot runs your application on port 8080. You can change this by adding the following in your application.properties:

server.port=9090

Or in application.yml:

server:

  port: 9090

💡 Tip: You can set server.port=0 to make Spring Boot choose a random free port — useful for integration tests.

❌ Common Mistake: Changing the port in @Bean methods like TomcatServletWebServerFactory but forgetting to remove server.port from application.properties can cause confusion. Properties file wins unless overridden by command-line args.

🔒 Enabling HTTPS in Spring Boot

To enable HTTPS, you’ll need a keystore file (e.g., keystore.p12) and then configure Spring Boot:

server.port=8443

server.ssl.key-store=classpath:keystore.p12

server.ssl.key-store-password=changeit

server.ssl.keyStoreType=PKCS12

server.ssl.keyAlias=tomcat

💡 Unknown Fact: Spring Boot can run HTTP and HTTPS together — just define another TomcatConnectorCustomizer bean for port 8080 while keeping 8443 as HTTPS.

❌ Common Mistake: Using a self-signed certificate in production without adding it to the truststore will break API calls from browsers and other services.

🚫 Disabling the Web Server

If you’re creating a non-web application (like a batch job or CLI tool), you can disable the embedded server:

@SpringBootApplication

public class MyApp {

    public static void main(String[] args) {

        SpringApplication app = new SpringApplication(MyApp.class);

        app.setWebApplicationType(WebApplicationType.NONE);

        app.run(args);

    }

}

Or via properties:

spring.main.web-application-type=none

💡 Tip: This reduces startup time and memory usage since Tomcat/Jetty/Undertow is not loaded.

❌ Common Mistake: Developers forget to remove web-related beans/controllers when disabling the server — Spring will still try to load them and fail.

📦 Default Packaging Type in Spring Boot

When you create a Spring Boot project using Spring Initializr, the default packaging type is JAR. This means the embedded server (Tomcat, by default) is inside your packaged app, so you can run it with:

java -jar myapp.jar

💡 Extra Info: You can switch to WAR if you want to deploy in external servers like Apache Tomcat — just change <packaging>war</packaging> in Maven.

❌ Common Mistake: Switching to WAR but forgetting to extend SpringBootServletInitializer will cause the app not to start on an external server.

📄 application.properties vs application.yml

Both are used for externalizing configuration, but:

• application.properties: Key-value format, simpler, familiar for many developers.
• application.yml: YAML format, supports hierarchy, cleaner for nested configs.

💡 Extra Info: Spring Boot loads both by default — if both exist, application.properties overrides application.yml for the same property.

❌ Common Mistake: Using tabs in .yml — YAML does not support tabs, only spaces, causing ScannerException.

🧩 How Profiles Work in Spring Boot

Profiles let you group configurations for different environments (dev, test, prod). You can create files like:

application-dev.properties

application-prod.properties

Activate a profile via:

spring.profiles.active=dev

💡 Unknown Fact: You can activate multiple profiles at once using spring.profiles.active=dev,qa.

❌ Common Mistake: Forgetting to set the active profile in production — your app might accidentally run with dev settings (like an in-memory DB).

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🎬 Wrapping Up

Wow! Today we explored some of Spring Boot’s hidden gems — from changing server ports 🖥️, enabling HTTPS 🔐, disabling the web server 🚫, understanding default packaging 📦, comparing application.properties vs application.yml 🗂️, to managing profiles 🌱.

💡 Here’s what you should take away:

• Spring Boot makes life easier, but small misconfigurations (wrong port, YAML indentation, wrong profile) can cause big headaches 😅
• Always double-check your spring.profiles.active and SSL setups before deploying to production ⚠️
• Use embedded servers wisely — or disable them for non-web apps to save resources 💪
• Know when to use JAR vs WAR packaging depending on deployment targets 🏗️

🔥 My challenge to you: Try these configs in a small test project and see how changing one thing can affect the entire app. It’s a fun way to learn & remember! 🚀

💬 I’d love to hear from you: Which Spring Boot trick surprised you the most? Drop your thoughts in the comments below 👇 — let’s learn together!

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