In this article, we're going to be looking at how to use Gitlab CI/CD to build, test and deploy a Spring Boot web application to a server instance. Gitlab has a generous offering of unlimited free private repositories and 2000 minutes of CI/CD runner. We will be using Gitlab as our cloud Git repository in this article and we encourage you to if you don't already have one. create an account Application Setup For the purpose of this article, we will create a simple Spring Boot application using . After downloading the generated project, the should look like this: Spring Initializr pom.xml <dependencies>                                             
	<dependency>                                           
		<groupId>org.springframework.boot</groupId>        
		<artifactId>spring-boot-starter-web</artifactId>   
	</dependency>                                          
                                                           
	<dependency>                                           
		<groupId>org.springframework.boot</groupId>        
		<artifactId>spring-boot-starter-test</artifactId>  
		<scope>test</scope>                                
	</dependency>                                          
</dependencies> Next, let's create a controller mapping for the index endpoint. The endpoint will simply return a hello world string concatenated with the current timestamp: @Controller                                           
public class IndexController {                        
                                                      
	@GetMapping("/")                                  
	@ResponseBody                                     
	public String index() {                           
		return "Hello World " + LocalDateTime.now();  
	}                                                 
                                                      
} We can test the new endpoint by starting the application and visiting from our browser, we should see the hello world string. Now that we have a working application, we need to create a new project on Gitlab, commit our code locally and push it to the remote repo using the project URL generated by Gitlab. http://localhost:8080 Let's execute the following commands from the project's root directory on our local machine: git init
git add .
git commit -m "initial commit"
git remote add origin https://gitlab.com/SeunMatt/gitlab-ci-demo.git
git push origin master Note that your project URL will be slightly different depending on the chosen username and project name. Server Setup For this tutorial, we will create a new , install JRE (Java Runtime Environment) and Nginx on it. DigitalOcean droplet Nginx will serve as a reverse proxy server that will run on port 80 and forward HTTP traffic to our Spring Boot application that will be running on port 8080 internally. We'll be using the Terraform configuration files from to provision the droplet. another article Gitlab CI/CD In this section, we're going to see how we can configure Gitlab to auto-deploy our Spring Boot application whenever we push new changes. We'll start by adding .gitlab-ci.yml to our project, then create a new CI/CD user on the server and finally define our pipeline with the necessary scripts. Application Building . In order for us to use Gitlab CI/CD, we need to add a file to the root of our project directory .gitlab-ci.yml The is a simple plaintext file that defines the jobs we want to execute and what scripts we want to run in each job. Let's create a file in our project's root directory with the following content: .gitlab-ci.yml .gitlab-ci.yml stages:
 - build
 - deploy The snippet above defines two stages that should run in the order they appear. We can see stages as a grouping of one or more jobs. The combination of different stages makes a pipeline. The name of each stage should reflect the type of job(s) in it. For example, the stage will have jobs that test and package our application as a jar file, whereas the stage will contain jobs that copy the generated jar file to the server. build deploy Let's define a job that will run the Maven package command and generate a single jar file. We will call the job : maven-build maven-build:
  image: maven:3-jdk-11
  stage: build
  script: "mvn package -B"
  artifacts:
    paths:
      - target/gitlab-ci-demo.jar In the snippet above, we configured the job to use a docker container that contains Maven version 3 and JDK 11. The keyword indicates that this job belongs to the stage, and the keyword indicates what command to execute in the docker container once it's ready. stage build script Another special keyword to take note of is . It instructs Gitlab CI/CD runner to preserve the end result of our command so we can use it in subsequent jobs. In this case, we're keeping the final jar file so we can reference it in the coming sections. artifacts script The complete file looks like this: .gitlab-ci.yml stages:                          
 - build                         
 - deploy                        
                                 
maven-build:                     
  image: maven:3-jdk-11          
  stage: build                   
  script: "mvn package -B"       
  artifacts:                     
    paths:                       
      - target/gitlab-ci-demo.jar To see this in action, let's commit and push our changes to Gitlab. Gitlab will auto-detect the file and trigger Gitlab CI/CD runner. .gitlab-ci.yml : We can monitor the progress of the running jobs on Gitlab by going to the CI/CD menu >> Jobs We can click on the running button to see the live output from the different commands. Once the build is complete, the running button will change to green and the text will now be : passed Application Deployment For our deployment process, we will first create a CI/CD user on our server, then use the command to copy the jar file from Gitlab to our server. scp Once the jar file is on our server, we will ssh to the server, move the jar file to the appropriate directory and restart the application service using . systemctl Let's SSH into the server instance we provisioned earlier and execute the following commands to create and configure the CI/CD user: adduser --quiet --shell $SHELL --disabled-password --gecos 'GitlabCI User' gitlab-ci
usermod -a -G sudo gitlab-ci
echo 'gitlab-ci:changemepassword' | chpasswd
printf 'Match User gitlab-ci\n\tPasswordAuthentication yes\n' >> /etc/ssh/sshd_config
systemctl restart sshd
echo 'gitlab-ci ALL=(ALL) NOPASSWD: /bin/mv, NOPASSWD: /usr/bin/systemctl, NOPASSWD: /bin/cp' | sudo EDITOR='tee -a' visudo First, we created a new user and then we change the user's password to . Then we updated the file to allow our new user to authenticate via password and we restart the service. gitlab-ci changemepassword ssh_config sshd The last command is very important, it disables prompting for password when we execute any of the following commands: , and . sudo mv systemtctl cp We need to set this because we'll be using the user in an automated process devoid of human intervention to supply a password. sudo We need to add 's password as an environment variable on Gitlab so that we can reference it, securely, in our file. To do that, we need to login to our . gitlab-ci .gitlab-ci.yml Gitlab account >> Settings >> CI/CD >> Variables Once we expand the section, we will see the button to add a new variable, we should click on it to add the variable: Variables Now that we have created our user and added the user's password to CI/CD variable on Gitlab, let's update our . file with the job: gitlab-ci.yml deploy deploy-master:                                                                                                                                  
  before_script:                                                                                                                                
    - apt-get update -qq && apt-get install -y -qq sshpass                                                                                      
  stage: deploy                                                                                                                                 
  script:                                                                                                                                       
    - sshpass -V                                                                                                                                
    - export SSHPASS=$CI_USER_PASS                                                                                                              
    - sshpass -e scp -o StrictHostKeyChecking=no target/gitlab-ci-demo.jar gitlab-ci@167.172.188.139:/home/gitlab-ci                            
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo mv /home/gitlab-ci/gitlab-ci-demo.jar /opt/java/webapps     
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo systemctl restart gitlab-ci-demo.service In this job definition, we use to specify what command should be executed on the server before executing other commands in the script tag. Additionally, in the section, we exported the password for the CI user into the current environment as . before_script script SSHPASS By so doing, will auto-respond to password prompts from and commands with the value of the environment variable sshpass ssh scp SSHPASS. The SSH commands we executed are pretty straightforward, we first use to copy the file to the server and then we move the file to the right directory and finally restarted the service using . scp systemtctl The complete . fill will have the following contents: gitlab-ci.yml stages:                                                                                                                                         
 - build                                                                                                                                        
 - deploy                                                                                                                                       
                                                                                                                                                
maven-build:                                                                                                                                    
  image: maven:3-jdk-11                                                                                                                         
  stage: build                                                                                                                                  
  script: "mvn package -B"                                                                                                                      
  artifacts:                                                                                                                                    
    paths:                                                                                                                                      
      - target/gitlab-ci-demo.jar                                                                                                               
                                                                                                                                                
deploy-master:                                                                                                                                  
  before_script:                                                                                                                                
    - apt-get update -qq && apt-get install -y -qq sshpass                                                                                      
  stage: deploy                                                                                                                                 
  script:                                                                                                                                       
    - sshpass -V                                                                                                                                
    - export SSHPASS=$CI_USER_PASS                                                                                                              
    - sshpass -e scp -o StrictHostKeyChecking=no target/gitlab-ci-demo.jar gitlab-ci@167.172.188.139:/home/gitlab-ci                            
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo mv /home/gitlab-ci/gitlab-ci-demo.jar /opt/java/webapps     
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo systemctl restart gitlab-ci-demo.service Let's commit our changes and push. As usual, Gitlab will start the runner automatically and we can monitor the progress of the pipeline. Once the pipeline has passed, we can navigate to our domain/IP address and see our web application running. Addendum With what we've set up so far, every time we push to our git repository, Gitlab will build and deploy. What if we want Gitlab to only deploy if we push to master? We can easily achieve that by adding a tag to the : rules deploy-master deploy-master:                                                                                                                              
  rules:                                                                                                                                    
    - if: '$CI_COMMIT_BRANCH =~ /^master$/'                                                                                                 
  before_script:                                                                                                                            
    - apt-get update -qq && apt-get install -y -qq sshpass                                                                                  
  stage: deploy                                                                                                                             
  script:                                                                                                                                   
    - sshpass -V                                                                                                                            
    - export SSHPASS=$CI_USER_PASS                                                                                                          
    - sshpass -e scp -o StrictHostKeyChecking=no target/gitlab-ci-demo.jar gitlab-ci@167.172.188.139:/home/gitlab-ci                        
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo mv /home/gitlab-ci/gitlab-ci-demo.jar /opt/java/webapps 
    - sshpass -e ssh -tt -o StrictHostKeyChecking=no gitlab-ci@167.172.188.139 sudo systemctl restart gitlab-ci-demo.service This way, if we push to any other branch other than , only the job will run. However, if we merge or push to the branch both and will run. master maven-build master maven-build deploy-master Conclusion In this article, we've looked at the basics of setting up a CI/CD pipeline on Gitlab and in the process we deployed a simple Spring Boot application. Gitlab CI/CD has more capabilities and features than those mentioned, I encourage you to read the to know more. The complete source code is . official documentation available on Gitlab You can follow me on Twitter to see more of my articles and tech musings https://twitter.com/SeunMatt2 Also published on: https://smattme.com/blog/technology/auto-deploy-spring-boot-app-using-gitlab-ci-cd

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