Fixing “Port 8080 was already in use” in Spring Boot on Windows

If your Spring Boot application fails to restart even after stopping it in STS or your IDE, and you see this message:

APPLICATION FAILED TO START

Description:

Web server failed to start. Port 8080 was already in use.

the issue is usually a stale Java process still running in the background.

In my case, the blocking process was javaw.exe.

Symptoms

Your application starts normally:

• Spring context loads


• database connection works


• Liquibase runs


• Hibernate initializes
  Then it fails at the end with:

Web server failed to start. Port 8080 was already in use.

This means the application itself is fine only the port is blocked.

Root cause

Stopping the server from STS/IDE does not always kill the underlying Java process.

A hidden javaw.exe may still be listening on port 8080.

Solution using Windows CMD

1. Check which PID is using port 8080

netstat -ano | findstr :8080

Example output:

TCP 0.0.0.0:8080 0.0.0.0:0 LISTENING 10728

TCP [::]:8080 [::]:0 LISTENING 10728

The last number is the PID.

2. Identify the process

tasklist /FI "PID eq 10728"

Example output:

javaw.exe 10728

3. Kill the process

taskkill /PID 10728 /F

Example result:

SUCCESS: The process with PID 10728 has been terminated.

4. Verify the port is free

netstat -ano | findstr :8080

If nothing is returned, port 8080 is free and you can restart your app.

Optional workaround

If needed, run your app on another port temporarily:

server.port=8081

Hope this helps!

Happy Coding!

Thanks,

Kailash

JavaCharter