How to Deploy Spring Boot to Heroku: Step-by-Step Guide

To deploy a Spring Boot app to Heroku, first create a Heroku app and add a Procfile specifying how to run your app. Then build your app with ./mvnw clean package and push your code to Heroku using git push heroku main. Heroku will detect the Java app, build it, and run it automatically.

Syntax

Deploying Spring Boot to Heroku involves these key parts:

• Procfile: Tells Heroku how to start your app.
• pom.xml or build.gradle: Defines your Java build and dependencies.
• Heroku CLI commands: Used to create app, add git remote, and push code.

bash

web: java -Dserver.port=$PORT -jar target/*.jar

Example

This example shows a simple Spring Boot app deployment to Heroku using Maven.

Steps:

• Create a Procfile with the command to run your jar.
• Build your app with Maven wrapper.
• Initialize git, create Heroku app, and push code.

bash

# Procfile content
web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jar

# Terminal commands
./mvnw clean package
heroku create my-spring-app
git init
heroku git:remote -a my-spring-app
git add .
git commit -m "Deploy Spring Boot to Heroku"
git push heroku main

Output

remote: -----> Java app detected
remote: -----> Building Java app with Maven
remote: -----> Launching...
remote:        Released v1
remote:        https://my-spring-app.herokuapp.com/ deployed to Heroku

Common Pitfalls

Common mistakes when deploying Spring Boot to Heroku:

• Not creating a Procfile or having wrong command causes app not to start.
• Forgetting to set server.port to $PORT environment variable.
• Not committing all files before pushing to Heroku.
• Using the wrong branch name when pushing (Heroku expects main or master).

bash

Wrong Procfile:
web: java -jar target/demo.jar

Right Procfile:
web: java -Dserver.port=$PORT -jar target/demo.jar

Quick Reference

Step	Command / File	Description
1	Procfile	Defines how Heroku runs your app with port binding
2	./mvnw clean package	Builds your Spring Boot jar file
3	heroku create	Creates a new Heroku app
4	git init	Initializes git repository if not done
5	heroku git:remote -a	Adds Heroku git remote
6	git add . && git commit -m 'msg'	Commits your code
7	git push heroku main	Pushes code to Heroku to trigger deployment

Key Takeaways

Always include a Procfile with the command to run your Spring Boot jar on Heroku.

Set the server port to Heroku's $PORT environment variable in the Procfile command.

Build your app with Maven or Gradle before deploying to Heroku.

Use Heroku CLI to create the app and push your code via git.

Commit all necessary files and push to the correct branch (usually main).