Build a Simple Jenkins‑Maven‑Git CI/CD Pipeline for Java Applications

Prerequisites

Three servers are required:

gitlab99 – 192.168.40.99 – 8C8G – GitLab installed

jenkins98 – 192.168.40.98 – 4C4G – Jenkins, JDK, Maven, Git installed

test97 – 192.168.40.97 – 2C2G – JDK installed (used as the deployment target)

1. GitLab Project Setup

Create a group and a blank project in GitLab:

Navigate to Your work / Groups / New group → Create group → fill the group name and click Create group.

Inside the group, click New project, select Blank project, enter a project name and click Create project.

Generate a personal access token (e.g., glpat‑qx7VU3J219j1D4_92uqJ) via Preferences → Access Tokens and copy it.

2. IDE (IntelliJ IDEA) Project Creation

Create a new Spring Web project and change the default port: server.port=8088 Add a simple controller:

@RestController
@RequestMapping("/")
public class HelloController {
    @RequestMapping
    public String sayHello() {
        return "Hello dev";
    }
}

Test locally with http://127.0.0.1:8088.

3. Jenkins CI/CD Configuration

3.1 Install Maven Plugin

In Jenkins go to

Dashboard → Manage Jenkins → Manage Plugins → Available

, search for "Maven" and install the plugin.

3.2 Create a Jenkins Job

Navigate to Dashboard → New Item, give the job a name (e.g., first), select Freestyle project, and click OK.

3.3 Configure Source Code Management

Under Source Code Management → Git, add the GitLab repository URL and the access token as credentials.

3.4 Configure Build Step

Add a Maven build step with goals clean package. Ensure the Maven installation path is set under

Dashboard → Manage Jenkins → Global Tool Configuration → Maven

(e.g., /opt/maven).

3.5 Post‑Build Actions – SSH Publisher

Install the SSH Publisher plugin (Dashboard → Manage Jenkins → Manage Plugins → Available → search "SSH Publisher"). Then configure:

Source files : **/jenkins‑*.jar (searches the workspace /root/.jenkins/workspace/first/target)

Remote directory : /root (or a custom path on the test server)

Enable Remove prefix with value /target to avoid nesting the jar.

3.6 Pre‑Build Steps – Clean Script

Create a shell script clean.sh on the test server ( /root) to stop the previous Java process and delete old jars:

#!/bin/bash
appname=$1
if [ -z $appname ]; then
    echo "Application name required!"
    exit -1
else
    echo "Application name is $appname"
fi
# Remove old jar files
rm -rf $appname/*.jar
# Find running java process for the app
pid=$(ps -ef | grep $appname | grep 'java -jar' | awk '{print $2}')
if [ -z $pid ]; then
    echo "$appname is not started"
else
    kill -9 $pid
    echo "$appname was stopped"
fi

Make it executable: chmod 777 clean.sh.

Configure the Jenkins job to run this script in Pre Steps (e.g., ./clean.sh jenkins-study).

3.7 Execute Remote Command to Run the Jar

In Post Steps → Send files or execute commands over SSH , add an Exec command such as:

nohup java -jar /root/jenkins-study/jenkins*.jar >> /root/jenkins-study/log.out 2>&1 &

This runs the jar in the background, redirects output to log.out, and ensures the process survives after the SSH session ends.

4. Testing the Pipeline

After configuring the job, click Build Now . Jenkins will:

Run clean.sh to stop any previous instance and delete old jars.

Pull the latest code from GitLab, build the jar with Maven, and archive it.

Transfer the jar to the test server via SSH.

Execute the nohup command to start the application.

Verify on the test server:

# jps
21562 jenkins-study-0.0.1-SNAPSHOT.jar
21610 Jps

Access the running service in a browser at http://192.168.40.97:8088 and you should see the "Hello dev" response.

5. Common Issues & Fixes

Missing Main Manifest : Ensure spring-boot-maven-plugin is not disabled ( skip=false) in pom.xml.

"java" command not found : Add JAVA_HOME and update PATH in /etc/bashrc on the test server.

Port already in use : The clean script stops the previous Java process before starting a new one, preventing the 8088 port conflict.

6. Summary

This guide demonstrates a complete CI/CD workflow using Jenkins, Maven, and GitLab to automatically build, transfer, and run a Spring Boot application on a remote test server, including pre‑build cleanup and post‑build deployment steps.