Jenkins provides many interfaces and extension points to enable users to customize and extend its functionality. In this book, we will explore these interfaces in depth and provide practical real-world examples that will take your usage of Jenkins to the next level.
In this book, you will learn how to develop and test your own Jenkins plugin, find out how to set up fully automated build pipelines and development processes, discover how to interact with the API and CLI, and how to enhance the user interface.
Chapter 1, Preparatory Steps, will cover the initial setup steps—getting your development environment set up, an overview of Jenkins and some options to install and run it as well as extend the basic setup. We will also review the principles of Continuous Integration, which are explored in greater detail later.
Chapter 2, Automating the Jenkins UI, will discuss how several common issues and bottlenecks may be alleviated through the automation and adaptation of the Jenkins frontend. Here, we will look at four fairly typical use cases, identify the root cause of the issues, and propose some possible improvements that can be made through the alteration and automation of the GUI.
Chapter 3, Jenkins and the IDE, builds on the Continuous Integration principals that we looked at earlier and provides an introduction to the Mylyn project.
It then details how to set up a process that enables developers to interact with Jenkins directly from within their IDE. A selection of examples covers Eclipse, NetBeans, and IntelliJ.
Chapter 4, The API and the CLI, illustrates how we can automate and extend Jenkins through its API and CLI. In this chapter, we will illustrate how to use these interfaces by working through the high-level "building blocks" of an example "Information Radiator" project.
This chapter will explain how to create a dynamic application that consumes information from Jenkins via its exposed interfaces.
We will also review other ways in which you could extend Jenkins via the CLI—by kicking off jobs and making other changes to Jenkins automatically and remotely.
Chapter 5, Extension Points, introduces many important concepts that provide a foundation for the Jenkins Extension points topics in the subsequent chapters. We will run through Java interfaces, Design by Contract, abstract classes, and Singletons. We will then take a look at how these patterns are used in the real world when we define our own Extension Point in Jenkins.
Chapter 6, Developing Your Own Jenkins Plugin, will combine the skills, concepts, and tools from the preceding chapters to build our first Jenkins plugin.
We will take a look at Maven and learn how to set it up and use it for Jenkins plugin development. We will then create our first Jenkins plugin, learn how to install it locally, and then learn how to quickly make, build, and deploy subsequent changes using Maven.
Chapter 7, Extending Jenkins Plugins, makes use of a simple plugin with the "Hello world" functionality we created in the previous chapter to keep the focus on getting to grips with the processes and tools. This chapter takes a look at the best way to get started with adding your own implementations. You will learn how to reuse existing code and functionality and understand how and where to find them.
After taking a look at some existing plugins and using those as examples, we will then take a detailed look at some of the additional resources and technologies you could take advantage of in your own projects.
Chapter 8, Testing and Debugging Jenkins Plugins, explains how to test and debug your own code and how to apply the same approach to existing plugins for troubleshooting.
It covers running tests with Maven, examines some existing tests from a popular plugin, and uses these to demonstrate how you can adapt these approaches to suit your own projects.
We will also take a look at debugging live code through the IDE and show how to integrate these useful functions into popular development IDEs. The final section of this chapter will introduce the inbuilt Jenkins Logger Console.
Chapter 9, Putting Things Together, takes a look at how Jenkins can be extended to work with other technologies and languages. We will start off with a look at the Jenkins Scripting console and see how useful it can be when combined with some Groovy scripting by providing some examples. We will then discuss developing applications using Groovy, Grails, and Gradle as possible alternatives to Maven and Java. The final part of this chapter covers Jenkins and Docker and then discusses how to set up build and deployment pipelines for iOS and Android development.
The reader is assumed to have some working knowledge of Jenkins and programming in general, an interest in learning the different options to take things to the next level, and an inclination to understand how to customize and extend Jenkins to suit their requirements and needs.
This book is aimed primarily at developers and administrators who are interested in taking their interaction and usage of Jenkins to the next level—extending it to fit their needs, interacting with Jenkins via its interfaces, and developing their own custom unit-tested plugins.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "We can include other contexts through the use of the include directive."
A block of code is set as follows:
<html>
<head>
<meta http-equiv="refresh" content="5">
<style type="text/css">When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
<html>
<head>
<meta http-equiv="refresh" content="5">
<style type="text/css">Any command-line input or output is written as follows:
java -jar jenkins-cli.jar -s http://minty:8080/ get-job VeryBasicJob
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Note that the http://jenkins-ci.org/ home page also hosts Native Installers for many popular operating systems under the Native packages column."
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