Java project which can be deployed on Heroku

Local project location

• servlet1 (HelloServlet.Get message)
• servlet2a (no params, all students from the Db)
• servlet2b (param x=1 given, userById run)

Remote project location

• servlet1 (HelloServlet.Get message)
• servlet2a (no params, all students from the Db)
• servlet2b (param x=1 given, userById run)

Heroku step-by-step instruction

• install heroku cli link
• create and upload ssh keys link
• check whether everything is ok (locally): mvn clean install && heroku local web
• to login to heroku server, run in the command line heroku login (browser will be opened for further authorization)
• to create a new app on heroku server, run in the command line heroku create, output should look like this:

Creating app... done, ⬢ young-garden-08016
https://young-garden-08016.herokuapp.com/ | https://git.heroku.com/young-garden-08016.git

• look for the git remotes: git remote -v, output should look like this:

heroku  https://git.heroku.com/young-garden-08016.git (fetch)
heroku  https://git.heroku.com/young-garden-08016.git (push)
origin  https://github.com/alexr007/java-heroku-from-zero-to-hero.git (fetch)
origin  https://github.com/alexr007/java-heroku-from-zero-to-hero.git (push)

• push your code to heroku git push heroku master

Adding heroku database:

• go to heroku dashboard
• click young-garden-08016 (your app name)
• click Resources
• in the add-ons type: Postgres
• click Heroku Postgres
• click Provision
• click Heroku Postgres in the list below
• go to Settings, look for Credentials (you can use them in your DataGrip)

Useful heroku command:

• heroku ps
• heroku open
• heroku ps:scale web=1
• heroku logs --tail

Pay your attention to

• Procfile contents:
  • fully-qualified path to the main class
  • classpath declaration
• pom.xml sections:
  • <packaging>jar
  • <pluginns>maven-dependency-plugin...

Note: be aware of Heroku env variables:

• DATABASE_URL looks like postgres:...
• JDBC_DATABASE_URL looks like jdbc:postgresql:...
• PORT http port to listen

Links

• Heroku official documentation in general: here
• Heroku official documentation about JDBC connection: here
• Heroku official github code: here
• Baeldung link how to create runnable jar file: here