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This document, together with the hello-world plugin, shows you how to get started with the plugin development.

Important!

Please first read the "before writing a plugin" page.

There are a lot of existing Jenkins plugins and a lot of people with Jenkins plugin development experience that you can take advantage of!

Check whether there is an existing plugin you can already use, or contribute to, then get in touch via the jenkinsci-dev mailing list, or IRC and explain your plugin idea.
Either we can point you towards an existing plugin, useful APIs, or code snippets that would be helpful.

Table of Contents

Table of Contents
styledisc

What Can Plugins Do?

Hudson Jenkins defines extensibility points, which are interfaces or abstract classes that model an aspect of a build system. Those interfaces define contracts of what need needs to be implemented, and Hudson Jenkins allows plugins to contribute those implementations. See this document for more about extension points.

In this document, we'll be implementing a Builder that says hello. (built-in builders include Ant, Maven, and shell script. Builders build a project.)

...

To develop a plugin, you need Maven 23 (why?) and JDK 56.0 or later. If this is the first time you use are using Maven, make sure Maven can download stuff over the internet.

Next, you'll have to have Maven download the necessary tools for you. Create an empty directory, download this pom.xml in there, and run "mvn package". This should download a bunch of tools.

No Format

$ cd /tmp
$ wget https://hudson.dev.java.net/source/browse/*checkout*/hudson/hudson/tools/bootstrap/pom.xml
$ mvn package
$ rm pom.xml

...

Note
titleNexus Users

If you are using the Nexus Maven Repository Manager, you can ignore these instructions, and instead, click here for instructions on how to add Jenkins build prerequisites and the proper settings.xml entries.

It may be helpful to add the following to your ~/.m2/settings.xml (Windows users will find them in c:\Documents and Settingsyourname\%USERPROFILE%\.m2\settings.xml):

No Format
Code Block
xml
xml
<settings>
  <pluginGroups>
    <pluginGroup>org.jenkins-ci.tools</pluginGroup>
  </pluginGroups>

  <profiles>
    <!-- Give access to Jenkins plugins -->
    <profile>
      <id>jenkins</id>
      <activation>
        <activeByDefault>true</activeByDefault> <!-- change this to false, if you don't like to have it on per default -->
      </activation>
      <repositories>
        <repository>
          <id>repo.jenkins-ci.org</id>
  <pluginGroups>        <url>https://repo.jenkins-ci.org/public/</url>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
          <id>repo.jenkins-ci.org</id>
    <pluginGroup>org.jvnet.hudson.tools</pluginGroup>
  </pluginGroups>

Note 1: If you are behind a http proxy, you will need to use Maven 2.0.5 or newer due to a known bug in Maven 2.0.4 and earlier accessing https:// repositories through a http proxy.

Note 2: MNG-2261 may cause you some problems locating plugins when you are in a directory with no pom.xml.

      <url>https://repo.jenkins-ci.org/public/</url>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  </profiles>
  <mirrors>
    <mirror>
      <id>repo.jenkins-ci.org</id>
      <url>https://repo.jenkins-ci.org/public/</url>
      <mirrorOf>m.g.o-public</mirrorOf>
    </mirror>
  </mirrors>
</settings>

This will let you use short names for Jenkins Maven plugins (i.e. hpi:create instead of org.jenkins-ci.tools:maven-hpi-plugin:1.61:create),
though this is unnecessary once you are already working in a plugin project (only useful for initial hpi:create).
Note that adding the Jenkins repositories in a profile like this is not really necessary since most (all?) plugins already define these repositories.
And the mirror declaration is probably unnecessary.

Creating a New Plugin

To start developing a new Jenkins plugin, use an IDE (below), or if you are more comfortable with Maven, run the following maven command:

No Format

$ mvn org.jvnet.hudson.tools:maven-hpi-plugin:1.7:create
archetype:generate -Dfilter=io.jenkins.archetypes:empty-plugin
Info

To create a plugin skeleton for Blue Ocean, please see the generator-blueocean-usain Yeoman generator.

This will ask you a few questionquestions, like the groupId (the maven Maven jargon for the package name) and the artifactId (the maven Maven jargon for your project name), then create a skeleton plugin from which you can start with.

Make sure you can build this:

No Format

$ cd newly-created-directory
$ mvn package

...

Building a Plugin

To build a plugin, run mvn install. This will create the file ./target/pluginname.hpi that you can deploy to Jenkins.

No Format
$ // if you are using IntelliJ
mvn install

Setting up a productive environment with your IDE

NetBeans

NetBeans users can use the IDE's Maven support to open the project directly.

As you navigate through the code, you can tell NetBeans to attach source code JAR files by clicking the "Attach" button that appears in the top of the main content window. This allows you to read the Jenkins core source code as you develop plugins. (Or just select Download Sources on the Dependencies node.)

You are advised to use the NetBeans plugin for Jenkins/Stapler development. This offers many Jenkins-specific features. Most visibly, create a new plugin using New Project » Maven » Jenkins Plugin, and use Run project to test it.

IntelliJ IDEA

IntelliJ 7.0 (or later) users can load pom.xml directly from IDE, and you should see all the source code of libraries and Jenkins core all the way to the bottom. Consider installing the IntelliJ IDEA plugin for Stapler to make the development easier.

Alternatively,emtpy create a new Maven project using Create from archetype and Add an Archetype. Select the GroupId and ArtifactId as above and choose RELEASE as version. In the next screen select io.jenkins.plugins as groupID and choose an artifactId (Project name) and Version to your liking. This will automatically create a maven project based on the specified artifact (e.g. empty-plugin).

Info

IntelliJ defaults to downloading sources and JavaDocs on demand. So, to see the source, you may need to click the Download artifacts button in the Maven Projects tab.

Eclipse

Use Eclipse Juno (4.2) or later for the best experience.

Note

Eclipse versions between 4.5 and < 4.6.2 contain a bug that causes errors such as "Only a type can be imported. hudson.model.Job resolves to a package".
If you encounter this error please upgrade to Eclipse Neon.2 (4.6.2) or higher (Bug 495598).

As Jenkins plugins are Maven projects, Eclipse users have two ways to load a Jenkins plugin project. One is to use m2e, which tries to make Eclipse understand Maven "natively", and the other is to use theusing maven, but Maven Eclipse plugin, which makes Maven generate Eclipse project definitions. At the moment, unless you have some prior experience with m2e, we currently recommend plugin developers to go with the Maven Eclipse plugin.

Eclipse users can run the following Maven command to generate Eclipse project files (the custom outputDirectory parameter is used to work around the lack of JSR-269 annotation processor support in Eclipse:)

No Format
$ mvn -DdownloadSources=true idea:idea
// if you are using Eclipse
$ mvn -DdownloadSources=true-DdownloadJavadocs=true -DoutputDirectory=target/eclipse-classes -Declipse.workspace=/path/to/workspace eclipse:eclipse 

NetBeans users should consider using this NetBeans module. Due to a bug in Eclipse, Eclipse users will need to remove src/main/resources from the source folder list after projects are imported to the workspace. See this e-mail thread for more details.

At this point, from your IDE, you should be able to see all files and all the needed libraries complete with their source code.

eclipse:configure-workspace

Where /path/to/workspace is the path to your Eclipse workspace.

Once this command completes successfully, use "Import..." (under the File menu in Eclipse) and select "General" > "Existing Projects into Workspace".

Note

Do not select "Existing Maven Projects", which takes you to the m2e route

See Jenkins plugin development with Eclipse for gotchas and other known Eclipse/Maven related issues with Jenkins plugin development.

See Eclipse alternative build setup for an alternative way of setting up the Eclipse build environment, that is a bit more technically involved than using Maven but can give faster build times.

Plugin Workspace Layout

The plugin workspace consists of the following major pieces, described in additional detail at Plugin Structure:

pom.xml

Maven uses it for building your pluginsrc/main/javaJava the pom.xml file to build your Jenkins plugin. All Jenkins plugins should be based on the Plugin Parent POM:

Code Block
xml
xml
<parent>
    <groupId>org.jenkins-ci.plugins</groupId>
    <artifactId>plugin</artifactId>
    <version>2.2</version>
</parent>

If the project is created using the provided archetype, everything is already set up. Up to Jenkins 1.645 the Plugin Parent POM was part of the main Jenkins project and the POM version was the baseline Jenkins version to be used for the plugin.

When using Parent POM version 2.2 or later, the baseline version is selection using the jenkins.version property, e.g.:

Code Block
xml
xml
<properties>
    <jenkins.version>1.609.1</jenkins.version>
</properties>

src/main/java

Java source files of the plugin.

src/main/resources

Jelly/Groovy views of the plugin. See this document for more about it.

...

Static resources of the plugin, such as images and HTML files.

Source Code

...

PluginImpl approach

(deprecated in favor of the Extension points approach below)

A plugin's main entry point is may be a PluginImpl class that extends from Plugin. Once Hudson Jenkins detects your this plugin class (via its @plugin javadoc annotation — this gets copied into manifest during the buildinheritance relationship from Plugin), it will create an instance, and invokes invoke methods.Most of the time, a plugin class just registers

Extension points approach

A Plugin class is optional; a plugin may simply implement extension points, registering them with the @hudson.Extension annotation for automatic detection by Jenkins.

The bulk of work in the plugin consists of implementing those extension points. See the sample source code for more information about how a Builder is implemented and what it does.

Developing a Plugin

Run Here are a few things about extension:

  • in general, a plugin extension should extend an existing extension point (a class that implements ExtensionPoint), and define an inner static class extending the corresponding descriptor (a class extending hudson.model.Descriptor)
  • the @Extension annotation must be placed on the inner descriptor class to let Jenkins know about this extension
  • the descriptor handles the global configuration of the extension while the extension class itself handles the individual configuration of the extension. For instance, the Setting context path
    in a plugin defining a class extending LabelAtomProperty, an object of this class is instantiated for each LabelAtom (provided that the plugin is activated by the user in the label's configuration page). If configuration parameters for each individual instance are required, they're handled via a config.jelly file stored in a resource package named after the extension class. When the configuration form is saved, Jenkins calls the extension constructor marked with the @org.kohsuke.stapler.DataBoundConstructor annotation, matching parameters by name

Debugging a Plugin

NetBeans 6.7+ users can just hit Debug. For all others, run the following command to launch Hudson Jenkins with your plugin:
Convenient:

No Format
mvnDebug hpi:run

Unix:

No Format
$ export MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000,suspend=n"
$ mvn hpi:run

Windows:

No Format
> set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000,suspend=n
> mvn hpi:run

If you open http://localhost:8080/jenkins in your browser, you should see the Hudson Jenkins page running in Jetty. The MAVEN_OPTS portion launches this whole thing with the debugger port 8000, so you should be able to start a debug session to this port from your IDE.

...

  1. When you make changes to view files in src/main/resources or resource files in src/main/webapp, just hit F5 in your browser to see the changes.
  2. When you change Java source files

    . Compile

    , compile them in your IDE (NetBeans 6.7+: Debug > Apply Code Changes) and Jetty should automatically redeploy

    Hudson

    Jenkins to pick up those changes. There is no need to run mvn at all.

    Info

    MAVEN_OPTS can be used to specify all sorts of other JVM parameters, like -Xmx

Changing port

If you need to launch the Jenkins on a different port than 8080, set the port through the system property jetty.port.

No Format
$ mvn hpi:run -Djetty.port=8090

Setting context path

maven-hpi-plugin 1.65 or later (used by parent POM 1.401 or later) can set the context path by using a system property. On more recent versions of Jenkins, the "/jenkins" prefix is added automatically.

No Format
$ mvn hpi:run -Dhpi.prefix=/jenkins

Changing code while debugging

Depending on what you change, you can see it in the running instance without restarting the whole Maven process:

  • Views: Groovy/Jelly views are re-compiled every time a browser requests a page, so just reload a page in the browser and you'll see the changes. This is also true for help files you write.
  • Java code: If you are debugging, JVM's hot swap feature can be used to reload code so long as you do not touch the method signature. (For example, from NetBeans use Debug » Apply Code Changes.) Beyond that, you can hit ENTER in the Maven process and it'll reload the Jenkins webapp, though generally, it is better to stop the process and start again. See Developing with JRebel for how to get a JRebel license for OSS projects to improve this experience.
  • POM: If you change POM, you'll have to stop and restart Maven to see the changes.

If you are using version 1.120 or later of maven-hpi-plugin, which would be the default when using version 2.16 or later of the plugin parent POM, you can use the same features to debug changes spanning multiple plugins, or even a custom build of Jenkins core. Just make sure you have SNAPSHOT dependencies set up between the associated Maven modules (<scope>test</scope> suffices), and that the upstream module(s) have been built (e.g., mvn -DskipTests clean install). Now hpi:run on the downstream plugin and you should be able to reload views defined in any of the linked modules.

Distributing a Plugin

To create a distribution image of your plugin, run the following Maven goalcommand:

No Format

$ mvn package

This should create target/*.hpi file. Other users can use HudsonJenkins' s web UI to upload this plugin to Hudson Jenkins (or place it in $HUDSON$JENKINS_HOME/plugins.)

...

Releasing a Plugin and Hosting a Plugin on jenkins-ci.org

If you got to this point, you should definitely consider hosting your plugin on jenkins-ci.org. Move on to this document for how to do that. This includes the instructions for releasing the plugin.

Using custom builds of plugins included in the Jenkins WAR

If you are building a patched version of one of the plugins in the Jenkins core, the deployment process is a bit different. This is because Jenkins will itself manage these plugins unless you tell it not to.

Deploying a custom build of a core plugin

  1. Stop Jenkins
  2. Copy the custom HPI file to $JENKINS_HOME/plugins
  3. Remove the previously expanded plugin directory
  4. Create an empty file called <plugin>.hpi.pinned - e.g. maven-plugin.hpi.pinned
  5. Start Jenkins

Other tips

  1. Consider running Maven like this mvn -o ... to avoid hitting repositories every time. This will make various operations considerably faster.
  2. Subscribe to users@hudson.dev.java.net the users' alias from here so that we can get in touch with you.
  3. When you bump up the version of Hudson Jenkins you depend on, make sure to run mvn clean once, in particular, to delte delete target/work that Jetty uses. Newer versions may just use work, not target/work. Otherwise, your Jetty may continue to pick up old left-over jar files.JAR files.
  4. If you have a high latency network connection to the Maven repository, you might find it faster to first run the build once on a server near to the maven repository, then rsync the .m2/repository folder across to your local computer
  5. The 'package' and 'install' targets will by default run many tests. You can add '-DskipTests' on the command-line to skip these (of course you should run the tests before committing any changes)
  6. The 'compiler:compile' goal is faster than 'compile', because it is a goal, rather than a lifecycle event, and therefore avoids certain earlier goals, such as setting up resources

Other resources

Besides this tutorial, there are other tutorials and examples available online: