Writing a Simple Jenkins Plugin

1. Introduction

Jenkins is a popular open-source automation server that supports building, deploying, and automating projects. Plugins are essential for extending Jenkins functionality. This lesson guides you through writing a simple Jenkins plugin.

2. Requirements

• Java Development Kit (JDK) 8 or above
• Maven 3.5 or later
• Jenkins installation (local or cloud-based)
• Basic understanding of Java and Maven

3. Plugin Structure

A Jenkins plugin typically consists of the following components:

• pom.xml: Maven configuration file.
• src/main/java: Java classes implementing plugin functionality.
• src/main/resources: Plugin configuration and resource files.

4. Development Setup

Follow these steps to set up your environment:

1. Install JDK and Maven on your machine.
2. Set up your Jenkins instance.
3. Create a directory for your new plugin.
4. Navigate to the directory and run the following command to create a new Maven-based Jenkins plugin:

mvn archetype:generate -Dfilter=io.jenkins.archetypes:

5. Writing the Plugin

Here's a basic example of a Jenkins plugin that prints "Hello, Jenkins!" in the console:

package com.example.helloworld;

import hudson.Extension;
import hudson.model.RootAction;

@Extension
public class HelloWorldAction implements RootAction {
    @Override
    public String getIconFileName() {
        return null; // No icon
    }

    @Override
    public String getDisplayName() {
        return "Hello World"; // Display name
    }

    @Override
    public String getUrlName() {
        return "hello"; // URL endpoint
    }
    
    public String sayHello() {
        return "Hello, Jenkins!";
    }
}

After writing your plugin, compile it using Maven:

mvn clean package

This will generate a .hpi file in the target directory, which you can install in Jenkins.

6. Best Practices

When developing Jenkins plugins, consider the following best practices:

• Follow naming conventions for classes and methods.
• Document your code and provide Javadoc comments.
• Maintain backward compatibility.
• Test your plugin thoroughly using Jenkins test harness.

7. FAQ