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Run the Application

info

For this document, we assume that you created a Spring Boot project using Spring Initializr. If you didn't, you can clone the monorepo I've prepared at https://github.com/franBec/springboot-demo-projects branch feature/initial-commit.

  1. Open IntelliJ IDEA → File → Open → Select the unzipped project folder.

  2. First-time JDK setup (if prompted):

    • IntelliJ will ask you to download a JDK. Choose the same version you selected in Spring Initializr (e.g., Java 21).
    • Click Download JDK and follow the prompts.

  3. Wait for background tasks:

    • Look for progress indicators in the lower-right corner (e.g., "Downloading Gradle dependencies" or "Indexing").
    • Let these finish, they set up your project's tools and libraries.

  4. Run the application:

    • Search for the Gradle tool window (in IntelliJ it's usually a small elephant icon on the right side).
    • Run the build command.
    • Run the bootRun command. Run Gradle App 029419c4eb3db1dc89730181b6349517

  5. Check the run terminal: After a few seconds, you'll see something similar to Tomcat started on port 8080 (http) with context path '/'. This means your Spring Boot app is live!

  6. Test it out: Go to http://localhost:8080. You'll see a Whitelabel Error Page. This is normal because we haven't done any development yet.

    Terminal
    $ w3m -dump http://localhost:8080
    Whitelabel Error Page

    This application has no explicit mapping for /error, so you are seeing this as
    a fallback.

Congratulations! Your Spring Boot app is up and running.

Here's why this is a big deal:

Before Spring Boot, getting a Java app to listen on a port like 8080 required hours of manual setup:

  • Configuring XML files (like web.xml).
  • Deploying WAR files to an external server (e.g., Tomcat).
  • Writing boilerplate code just to start the server.

Today with Spring Boot:

  • The embedded Tomcat server starts automatically.
  • Zero code needed: the main() method does everything.
  • No XML or manual server setup.

You just witnessed Spring Boot's magic: turning what used to be a days-long chore into a 10-second task. And we haven't even written a single line of our own code yet!