Embedded server concept in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when you run a Spring Boot app with an embedded server?

Consider a Spring Boot application with the default embedded Tomcat server. What is the behavior when you run the app?

A The app starts and listens on port 8080 without needing an external server.

B The app fails to start because an external Tomcat server is required.

C The app starts but does not listen on any port until manually configured.

D The app starts but only serves static files, no dynamic content.

💡 Hint

Think about what embedded means in this context.

Spring Boot includes an embedded Tomcat server by default, so the app runs standalone and listens on port 8080 without needing an external server.

📝 Syntax

intermediate

Which property sets the embedded server port in Spring Boot?

In application.properties, which property correctly sets the embedded server port to 9090?

A spring.server.port=9090

B server.embedded.port=9090

C embedded.server.port=9090

D server.port=9090

💡 Hint

Look for the standard prefix for server settings in Spring Boot.

The correct property to set the embedded server port is server.port. Other options are invalid keys.

🔧 Debug

advanced

Why does this Spring Boot app fail to start with embedded server?

Given this Spring Boot main class, why does the app fail to start the embedded server?

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

Spring Boot

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

A No embedded server dependency included in the project.

B Missing args parameter in run method causes failure.

C The @SpringBootApplication annotation is missing.

D The main method should return void, not static.

💡 Hint

Consider the dependencies required to auto-configure an embedded server.

The main class is correct and SpringApplication.run(MyApp.class, args) works fine, but without a dependency like spring-boot-starter-web, no embedded server (Tomcat) is included or auto-configured, so none starts.

🧠 Conceptual

advanced

What is the main advantage of using an embedded server in Spring Boot?

Why do developers prefer embedded servers in Spring Boot applications?

A It disables HTTP support to improve security.

B It improves the app's runtime performance by using native OS servers.

C It allows running the app as a standalone jar without installing a separate server.

D It forces the app to use only Tomcat as the server.

💡 Hint

Think about deployment simplicity and portability.

Embedded servers let you package the app with the server inside, so you can run it anywhere without extra setup.

❓ state_output

expert

What is the output when running this Spring Boot app with embedded server and custom port?

Given this application.properties and main class, what port will the embedded server listen on?

application.properties:
server.port=7070

Main class:
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

Spring Boot

application.properties:
server.port=7070

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

A The embedded server listens on default port 8080.

B The embedded server listens on port 7070.

C The app fails to start due to port conflict.

D The embedded server listens on port 80.

💡 Hint

Check how Spring Boot reads properties for server configuration.

The server.port property overrides the default 8080 port, so the embedded server listens on 7070.