Streamline Jenkins Pipelines with Shared Libraries: A Step-by-Step Guide

Introduction

When multiple Jenkins pipelines contain duplicated code, maintaining them becomes cumbersome; using a shared library lets you encapsulate common logic and call it from any pipeline, improving maintainability and version control.

Install Jenkins

Run Jenkins via Docker Compose:

$ mkdir jenkins && cd jenkins
$ sudo mkdir -p data
$ sudo chown 1000.1000 -R data
$ vim docker-compose.yml

version: '3.9'
services:
  jenkins-master:
    image: docker.io/jenkins/jenkins:2.377-jdk17
    container_name: jenkins
    hostname: jenkins
    restart: always
    privileged: true
    network_mode: 'host'
    volumes:
      - /etc/localtime:/etc/localtime:ro
      - ./data:/var/jenkins_home
    environment:
      - JAVA_OPTS='-Djava.util.logging.config.file=/var/jenkins_home/log.properties'
      - TZ=Asia/Shanghai

After starting Jenkins, install the Pipeline: Groovy Libraries and List Git Branches Parameter plugins.

Create a Shared Library

Prepare a Git repository with the following structure:

.
├── resources   # files needed during the build
│   └── build
│       └── mvn
│           ├── Dockerfile
│           └── settings.xml
├── src         # reusable Groovy classes
│   └── org
│       └── devops
│           ├── GlobalVars.groovy
│           └── tools.groovy
└── vars        # pipeline scripts
    └── pipeline01

Define common build methods in tools.groovy:

package org.devops

def gitCheckout(URL, credentialsId) {
    steps.checkout([
        $class: 'GitSCM',
        branches: [[name: '$BRANCH']],
        extensions: [],
        userRemoteConfigs: [[credentialsId: "${credentialsId}", url: "${URL}"]]
    ])
}

def gitMsg() {
    sh '''
        git show --stat --format=提交日期：%ci,%n提交人：%cn,%n提交备注：%s,%n提交Hash：%H,%n提交分支：%d,%n%b%n提交修改的文件：
    '''
}

def cleanWS() {
    cleanWs deleteDirs: true, notFailBuild: true
}

def creatFile(filename, content) {
    steps.writeFile encoding: 'UTF-8', file: "$filename", text: "$content"
}

def commitId() {
    String commit = steps.sh(returnStdout: true, script: 'git rev-parse --short HEAD').trim()
    return commit
}

def build(action, commitid, repourl, tag) {
    sh """
       # build
       DOCKER_BUILDKIT=1 docker build --progress=auto \
                 --target=${action} \
                 --build-arg version=${commitid} \
                 -t ${repourl}:${tag} .
       # push
       docker push ${repourl}:${tag} && docker rmi ${repourl}:${tag}
    """
}

def loginRepo(username, password, repourl) {
    sh """
      docker login -u $username -p $password $repourl
    """
}

Define global variables in GlobalVars.groovy:

package org.devops

class GlobalVars {
    static String giturl = 'https://example.com/example/test.git'
    static String certid = 'e6655bac-85cc-4a61-9ae3-3eeb02ff2e4c'
    static String imageRepo = 'harbor.example.cn/public'
    static String pushRepo = 'harbor.example.cn/public/test'
    static String userRepo = 'root'
    static String passRepo = 'root1234'
}

Define the Pipeline

@Library('jenkinslibrary@master') _

def GlobalVars = new org.devops.GlobalVars()

def tools = new org.devops.tools()

def buildfile = libraryResource "build/mvn/Dockerfile"

def mvnconf = libraryResource "build/mvn/settings.xml"

pipeline {
    agent any
    options {
        buildDiscarder logRotator(artifactDaysToKeepStr: '', artifactNumToKeepStr: '', daysToKeepStr: '5', numToKeepStr: '5')
        disableConcurrentBuilds()
        disableResume()
        skipDefaultCheckout()
        timestamps()
    }
    stages {
        stage('拉取代码') {
            steps {
                script {
                    tools.gitCheckout(GlobalVars.giturl, GlobalVars.certid)
                    tools.gitMsg()
                }
            }
        }
        stage('构建镜像') {
            steps {
                script {
                    def commitID = tools.commitId()
                    def imagetag = currentBuild.id
                    tools.creatFile('settings.xml', mvnconf)
                    tools.creatFile('Dockerfile', buildfile)
                    tools.loginRepo(GlobalVars.userRepo, GlobalVars.passRepo, GlobalVars.imageRepo)
                    tools.build('release', commitID, GlobalVars.pushRepo, imagetag)
                }
            }
        }
    }
    post {
        always {
            script { tools.cleanWS() }
        }
    }
}

Create Build Files

Dockerfile :

FROM docker.io/library/maven:3.8-openjdk-8-slim AS build
ENV TZ=Asia/Shanghai
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && \
    echo $TZ > /etc/timezone
WORKDIR /build
COPY settings.xml /root/.m2/
COPY . /build
RUN mvn -Dmaven.test.skip=true package

FROM docker.io/library/eclipse-temurin:8u332-b09-jre-focal AS release
ENV TZ=Asia/Shanghai
ARG version
EXPOSE 8080
WORKDIR /app
COPY --from=build /build/target/test-0.0.1-SNAPSHOT.jar app.jar
ENTRYPOINT java -server \
           ${JAVA_OPTS} \
           -jar /app/app.jar \
           --user.timezone=GMT+08 \
           --java.security.egd=file:/dev/./urandom ${JAVA_CLI}

settings.xml (Maven mirrors configuration) is also added to the repository.

Add the Shared Library in Jenkins

Navigate to Manage Jenkins → Global Pipeline Libraries and configure the library repository.