Extending the DSL

NOTE: The Job DSL extension point has been superseded by the Dynamic DSL. Consider the extension point as deprecated. It will be removed in the future.

Note: This page is intended for Jenkins plugin developers which want to provide DSL methods for their plugins. If you are a DSL user, have a look at the configure block, the user power moves and at the examples for hints about extending the DSL as a user.

Any Jenkins plugin can provide DSL methods for features they contribute to the job configuration by implementing the Job DSL extension point. The extension point is available with Job DSL plugin version 1.35 or later.

To be able to use the Job DSL extension point, the Job DSL plugin has to be added to the plugin's dependencies. The dependency should be marked as optional, so that the plugin can still be used without the Job DSL plugin.

Maven:

<project xmlns="http://maven.apache.org/POM/4.0.0" ...>
    ...
    <dependencies>
        ...
        <dependency>
            <groupId>org.jenkins-ci.plugins</groupId>
            <artifactId>job-dsl</artifactId>
            <version>1.86</version>
            <optional>true</optional>
        </dependency>
        ...
    </dependencies>
    ...
</project>

Gradle:

...
dependencies {
    ...
    optionalJenkinsPlugins 'org.jenkins-ci.plugins:job-dsl:1.86@jar'
    ...
}
...

A class extending javaposse.jobdsl.plugin.ContextExtensionPoint should contain all methods that the plugin wants to contribute to the DSL. The class should be marked as optional by using the @Extension(optional = true) annotation to gracefully disable the extension if the user is not using the Job DSL plugin.

Each method that should be available in the DSL must be marked with the @DslExtensionMethod annotation. The mandatory context attribute of the annotation specifies which DSL context should provide the method. Only DSL context classes implementing javaposse.jobdsl.dsl.helpers.ExtensibleContext can be extended, which includes the following classes and contexts:

• javaposse.jobdsl.dsl.helpers.ScmContext for the scm and multiscm contexts
• javaposse.jobdsl.dsl.helpers.step.StepsContext for the steps context
• javaposse.jobdsl.dsl.helpers.triggers.TriggerContext for the triggers context
• javaposse.jobdsl.dsl.helpers.triggers.MultibranchWorkflowTriggerContext for the triggers context, but only for multibranch workflow jobs
• javaposse.jobdsl.dsl.helpers.properties.PropertiesContext for the properties context
• javaposse.jobdsl.dsl.helpers.publisher.PublisherContext for the publisher context
• javaposse.jobdsl.dsl.helpers.wrapper.WrapperContext for the wrappers context
• javaposse.jobdsl.dsl.helpers.BuildParametersContext for the parameters context
• javaposse.jobdsl.dsl.helpers.publisher.MavenPublisherContext for the publishers context, but only for Maven jobs
• javaposse.jobdsl.dsl.helpers.triggers.MavenTriggerContext for the triggers context, but only for Maven jobs
• javaposse.jobdsl.dsl.helpers.wrapper.MavenWrapperContext for the wrappers context, but only for Maven jobs
• javaposse.jobdsl.dsl.helpers.AxisContext for the axes context of matrix jobs
• javaposse.jobdsl.dsl.helpers.IvyBuilderContext for the ivyBuilder context of Ivy jobs
• javaposse.jobdsl.dsl.helpers.common.DownstreamTriggerParameterContext for the parameters context of parameterized triggers
• javaposse.jobdsl.dsl.helpers.toplevel.EnvironmentVariableContributorsContext for the contributors context within the environmentVariables context

The parameters of the @DslExtensionMethod annotated method are the same parameters that will be available in the DSL. Have a look at the DSL Design section of the Job DSL contributing guide on how to use methods parameters.

The method can return an object that will be saved as part of the job configuration. Usually that will be the hudson.tasks.Builder, hudson.tasks.Publisher or hudson.tasks.BuildWrapper subclass which is provided by the plugin. If the method should not contribute to the job configuration, it can simply return null.

In the following example, a plugin provides an ExampleBuilder build step with two options, one with a string value and another one with an integer value. The Job DSL should be extended with an example method in the steps context so that DSL users can easily add the build step to their jobs.

job('example') {
    steps {
        example('foo', 42)
    }
}

To implement this DSL extension, a ContextExtensionPoint subclass must contains an example method with a matching signature. The method must return a pre-configured ExampleBuilder.

package org.jenkinsci.plugins.example;

import hudson.Extension;
import javaposse.jobdsl.dsl.helpers.step.StepContext;
import javaposse.jobdsl.plugin.ContextExtensionPoint;
import javaposse.jobdsl.plugin.DslExtensionMethod;

@Extension(optional = true)
public class ExampleJobDslExtension extends ContextExtensionPoint {
    @DslExtensionMethod(context = StepContext.class)
    public Object example(String optionA, int optionB) {
        return new ExampleBuilder(optionA, optionB);
    }
}

It is also possible to add nested DSL contexts from an extension point. The DSL uses Groovy closures to implement the contexts, but is possible to implement contexts without using Groovy. The closure object of the nested context is passed as a Runnable to the last parameter of the @DslExtensionMethod annotated method.

The closure must be executed in a DSL context, which is a class implementing the javaposse.jobdsl.dsl.Context marker interface and which will provide the DSL methods for the nested context. The executeInContext method inherited from ContextExtensionPoint should be used the run the closure in the nested context.

The example above can be changed to use a nested DSL context for the ExampleBuilder options.

job('example') {
    steps {
        example {
            optionA('foo')
            optionB(42)
        }
    }
}

A class implementing Context will provide the methods for the nested DSL context.

package org.jenkinsci.plugins.example;

import javaposse.jobdsl.dsl.Context;

public class ExampleDslContext implements Context {
    String optionA
    int optionB

    public void optionA(String value) {
        optionA = value;
    }

    public void optionB(int value) {
        optionB = value;
    }
}

The @DslExtensionMethod annotated method in the ContextExtensionPoint subclass has a single Runnable parameter, which will be executed using the custom Context class. It returns a new ExampleBuilder configured with values from the nested context.

package org.jenkinsci.plugins.example;

import hudson.Extension;
import javaposse.jobdsl.dsl.helpers.step.StepContext;
import javaposse.jobdsl.plugin.ContextExtensionPoint;
import javaposse.jobdsl.plugin.DslExtensionMethod;

@Extension(optional = true)
public class ExampleJobDslExtension extends ContextExtensionPoint {
    @DslExtensionMethod(context = StepContext.class)
    public Object example(Runnable closure) {
        ExampleDslContext context = new ExampleDslContext();
        executeInContext(closure, context);

        return new ExampleBuilder(context.optionA, context.optionB);
    }
}

In cases where it's necessary to perform additional actions after a job has been created or updated, the ContextExtensionPoint can act as a listener. Subclasses can override the notifyItemCreated and notifyItemUpdated methods to be notified about job creation or update events. The created or updated job is passed into the methods as Item along with a DslEnvironment. The DslEnvironment can be used to transfer state from a @DslExtensionMethod to the listener methods, which is useful when the listener methods needs access to the parameters of the @DslExtensionMethod. The @DslExtensionMethod needs to declare the DslEnvironment as one of it's parameters to get access to the DslEnvironment. The DslEnvironment parameter will not be exposed to the DSL.

DslEnvironment implements a java.util.Map<String, Object> interface and can store arbitrary data. Each job has a separate DslEnvironment and the DslEnvironment for a job will be shared between all ContextExtensionPoint instances, so a ContextExtensionPoint instance is able to see values stored by other instances. Subclasses of ContextExtensionPoint should choose unique keys to avoid collisions with other extensions.

The following example will show how to use the DslEnvironment to create an additional configuration file in the job's directory. The readFileFromWorkspace DSL method is used to read the content of the configuration file from the workspace of the seed job.

job('example') {
    steps {
        example('foo', readFileFromWorkspace('example-1.json'))
        example('bar', readFileFromWorkspace('example-2.json'))
    }
}

The @DslExtensionMethod uses the environment to store the content of the config file, so that is can be retrieved in the listener methods and be written to a file. The implementation does not need to distinguish between creation and update, so it delegates the creation event to notifyItemUpdated. A unique key for the DslEnvironment must be chosen because build steps can be added multiple times.

package org.jenkinsci.plugins.example;

import hudson.Extension;
import hudson.model.Item;
import javaposse.jobdsl.dsl.helpers.step.StepContext;
import javaposse.jobdsl.plugin.ContextExtensionPoint;
import javaposse.jobdsl.plugin.DslEnvironment;
import javaposse.jobdsl.plugin.DslExtensionMethod;
import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.util.Map;

@Extension(optional = true)
public class ExampleJobDslExtension extends ContextExtensionPoint {
    private static final String PREFIX = "example.";

    @DslExtensionMethod(context = StepContext.class)
    public Object example(String optionA, String configJson,
                          DslEnvironment dslEnvironment) {
        dslEnvironment.put(PREFIX + optionA, configJson);
        return new ExampleBuilder(optionA);
    }

    @Override
    public void notifyItemCreated(Item item,
                                  DslEnvironment dslEnvironment) {
        notifyItemUpdated(item, dslEnvironment);
    }

    @Override
    public void notifyItemUpdated(Item item,
                                  DslEnvironment dslEnvironment) {
        for (Map.Entry<String, Object> entry : dslEnvironment.entrySet()) {
            String key = entry.getKey();
            if (key.startsWith(PREFIX)) {
                String fileName = key.substring(PREFIX.length()) + ".json";
                File configFile = new File(item.getRootDir(), fileName);
                try {
                    FileUtils.write(configFile, (String) entry.getValue());
                } catch (IOException e) {
                    // handle exception
                }
            }
        }
    }
}

Instances of ContextExtensionPoint must be thread-safe. Each subclass will be instantiated only once and reused for all seed jobs. Since multiple seed jobs can run in parallel, any @DslExtensionMethod and the listener methods can be called in parallel.

To debug problems with Job DSL extensions, set the logger for javaposse.jobdsl to level FINE. The Jenkins log configuration can be changed at Manage Jenkins > System Log, e.g. by adding a new log recorder for javaposse.jobdsl.

The following plugins implement the extension point and serve as examples:

• JGiven Plugin