How to install spring boot app as a service and replace version by scp

In the time of microservices and Kubernetes most of the java applications are deployed as Docker containers (Kubernetes pods) and old-fashioned deployment to the application server or as an operating system service is rare but sometimes useful.

I will show how to simply install Spring boot application as a linux service and deploy the newer application version by the simple script.

At the beginning let’s assume we have ready Spring Boot application packaged as JAR file with embedded web server. Next to the JAR file we could put application.properties or application-{profile}.properties in order to parametrize application (see more about externalized configuration on Spring Boot documentation.

In this post I will show how to run Spring Boot app by the systemd. systemd is the successor of the System V init system and is now being used by many modern Linux distributions.

First of all create a service file in /etc/systemd/system named e.g. myapp.service with the following content:

[Unit]
Description=myapp
After=syslog.target

[Service]
User=root
WorkingDirectory=/var/app
ExecStart=/root/.sdkman/candidates/java/current/bin/java -jar /var/app/myapp.war
SuccessExitStatus=143

[Install]
WantedBy=multi-user.target

Remember to change the Description, User, and ExecStart fields for your application. In the above case the working directory is set to /var/app and the service is run by the root. It is not always the best solution from security perspective - you should create separate user account with proper permissions. You could also notice that ExecStart run normal java process and points to the generated Spring Boot application package. Because the java is not added to the path (you could use tools like SDKMAN) exec has full path to the java binary.

With the deployed app and prepared script notify systemd about the service:

systemctl daemon-reload

And enable service:

systemctl enable myapp.service

You could control new service with the give commands:

systemctl start myapp
systemctl stop myapp
systemctl restart myapp
systemctl status myapp

When we configure the server side we need a Bash script

#!/usr/bin/env bash

# configuration
SERVER="[email protected]"
KEY="~/.ssh/demo-server.pem"
APP_NAME=myapp

# prepare new jar/war (this is the old version of spring, with 2.X ./gradlew clean build)
./gradlew clean bootRepackage 
# stop remote service
ssh -i $KEY $SERVER "sudo systemctl stop $APP_NAME"
# move old var (backup old versions and logs - modify if needed)
ssh -i $KEY $SERVER "cp /var/app/$APP_NAME.war /var/app/\$(date +%F-%H:%M)_$APP_NAME.war && cp /var/app/$APP_NAME.log /var/app/\$(date +%F-%H:%M)_$APP_NAME.log"
# copy new app version to remote server
scp -i $KEY ./build/libs/*.war $SERVER:/var/app/$APP_NAME.war
# start remote service
ssh -i $KEY $SERVER "sudo systemctl start $APP_NAME"

It’s a general script which helps you to build, stop remote service, copy current app version and start new service. It should be enough when you have some kind of demo server and need fast option to redeploy application.