Dockerize Gradle application using Jenkins

In this challenge we will build and deploy a application using docker and Jenkins

1. A Gradle web project structure is given in the gradle webapp directory which is in the path mentioned below.
   dev/workspace/sample-project
2. Initialize the gradle webapp directory as a gradle project and configure the build script to
   - generate a war file
   - build a docker image named "gradle_image"
   - run the docker image on a container named "gradle_container", expose to the port 8001
3. Create a Dockerfile to deploy the generated war file in tomcat server
4. Initialize git to make gradle webapp directory as your local git repository.
5. Launch jenkins and create a declarative pipeline named gradle-build to run and deploy the gradle application.
6. Ensure that your Gradle application is running on http://localhost:8001/gradle_webapp

Let's get started...

1. Initialize the Gradle project:
Open the command prompt/terminal in the dev/workspace/sample-project directory.
Run the command gradle init and select the option 2: application and then select 1: Java
Now, the Gradle project is initialized in the 'dev/workspace/sample-project directory'

2. Configure the build script:
Open the 'build.gradle' file in the 'dev/workspace/sample-project' directory.
Add the following code to generate a war file:

apply plugin: 'war'
war {
    baseName = 'gradle_webapp'
    version = '1.0'
}
plugins {
    id 'com.spotify.docker' version '1.2.0'
}
docker {
    name 'gradle_image'
    copySpec.from war
    buildArgs(['TOMCAT_VERSION': '9.0.0.M26'])
}
task startContainer(type: DockerRunTask) {
    dependsOn buildDocker
    containerName 'gradle_container'
    imageId project.docker.imageId
    ports '8001:8080'
    daemonize true
    remove true
}

3. Create a Dockerfile:
Create a new file named Dockerfile in the dev/workspace/sample-project directory.
Add the following code to deploy the generated war file in Tomcat server:

FROM tomcat:9.0.0.M26-jre8
COPY build/libs/gradle_webapp-1.0.war /usr/local/tomcat/webapps/
CMD ["catalina.sh", "run"]

4. Initialize git:
Open the command prompt/terminal in the 'dev/workspace/sample-project directory'
Run the command 'git init'

5. Launch Jenkins and create a declarative pipeline:

Open Jenkins in your browser and login.
Click on "New Item" and enter a name for the pipeline (e.g. "gradle-build").
Select "Pipeline" and click "OK".
In the "Pipeline" section, add the following code:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'gradle clean build'
            }
        }
        stage('Docker Build') {
            steps {
                sh 'docker build -t gradle_image .'
            }
        }
        stage('Docker Run') {
            steps {
                sh 'docker run -p 8001:8080 --name gradle_container gradle_image'
            }
        }
    }
    post {
        always {
            sh 'docker stop gradle_container || true && docker rm gradle_container || true'
        }
    }
}

Ensure that the Gradle application is running on http://localhost:8001/gradle_webapp:

Open your browser and go to http://localhost:8001/gradle_webapp.
If the Gradle application is running successfully, you will see the default Tomcat homepage.

---THANK YOU---