Groovy Script For Jenkins

What is Groovy Script?

Groovy Script is a dynamic scripting language that runs on the Java Virtual Machine (JVM) and is designed to enhance and simplify Java programming. It combines the best features of Java with additional scripting capabilities, making it easier to write and read code. Groovy Script supports a wide range of programming paradigms, including object-oriented, functional, and imperative styles. It seamlessly integrates with existing Java libraries and frameworks, allowing developers to leverage the extensive Java ecosystem. Groovy Script is commonly used in various contexts, including web development, automation, build scripting, and as a scripting language for tools like Jenkins.

Configuration

The configuration of a Groovy script depends on the specific context in which it is being used. However, here are some common steps to configure a Groovy script:

• Environment Setup: Ensure that the required runtime environment is set up. This typically involves installing the Groovy language and ensuring that the necessary dependencies are in place.
• Script Creation: Create a new file with a ".groovy" extension or use an existing Groovy script file.
• Script Content: Write the desired logic and functionality in the Groovy script. This can include defining variables, functions, and classes, and implementing specific operations or tasks.
• Script Integration: Depending on the use case, the Groovy script may need to be integrated into a larger system or framework. For example, in the case of Jenkins, the script can be used within Jenkins pipelines or as a standalone script within a Jenkins job.
• Configuration Parameters: If the Groovy script requires any configuration parameters or inputs, ensure these are properly defined and passed to the script during execution.
• Testing and Execution: Validate the script by executing it in the appropriate environment. This involves running the script and verifying that it performs the expected actions or produces the desired output.
• Iterative Development: Iterate on the script as needed, making modifications or enhancements based on feedback or evolving requirements.

Usage of Groovy Script in Jenkins

Groovy scripts are extensively used in Jenkins for various tasks and customizations. Here are some common use cases for Groovy scripts for Jenkins:

• Pipeline Automation: Groovy is the scripting language used to define Jenkins pipelines. With Groovy, you can create complex workflows, define stages, steps, and conditions, and orchestrate the entire build, test, and deployment process.
• Job Configuration: Groovy scripts can be used to configure Jenkins jobs programmatically. This includes setting build parameters, defining triggers, configuring source code repositories, and setting up post-build actions.
• Build and Deployment Automation: Groovy scripts enable developers to define custom build and deployment processes. This can involve running specific commands, manipulating files and directories, integrating with external tools or APIs, and performing advanced logic during the build or deployment phase.
• Plugin Extensions: Groovy scripts can extend the functionality of Jenkins by interacting with Jenkins plugins. This includes triggering plugin actions, accessing plugin APIs, and customizing plugin behavior based on specific requirements.
• Scripted UI Interactions: Groovy scripts can interact with the Jenkins user interface (UI) to perform tasks such as creating or updating Jenkins configurations, managing credentials, and manipulating job settings.
• Script Console: Jenkins provides a built-in Script Console, where administrators can execute Groovy scripts directly on the Jenkins server. This allows for quick testing, troubleshooting, and performing administrative tasks.

Advantages of Groovy

Groovy offers several advantages as a programming language. Here are some key advantages of Groovy:

• Java Compatibility: Groovy seamlessly integrates with existing Java code and libraries. It can directly use Java classes, call Java methods, and inherit from Java classes, allowing for easy interoperability with the extensive Java ecosystem.
• Concise and Readable Syntax: Groovy has a concise and expressive syntax that reduces boilerplate code and increases readability. It provides shorthand notations, closures, and dynamic typing, making code more concise and easier to understand.
• Scripting Capabilities: Groovy is a dynamic scripting language that allows for rapid prototyping and scripting tasks. It offers features like scripting blocks, dynamic typing, and simplified syntax, enabling developers to quickly write and execute scripts.
• Easy Learning Curve: Groovy's syntax is similar to Java, making it easy for Java developers to learn and adopt. It inherits Java's object-oriented principles, reducing the learning curve for developers already familiar with Java.
• Metaprogramming and DSL Support: Groovy provides powerful metaprogramming capabilities, allowing developers to modify and enhance the behavior of existing classes at runtime. This enables the creation of Domain-Specific Languages (DSLs) and flexible APIs tailored to specific use cases.
• Testing and Automation: Groovy's flexible syntax and built-in testing frameworks make it ideal for writing test automation scripts. It supports behavior-driven development (BDD) frameworks like Spock, making it easy to write concise and expressive test cases.
• Gradual Typing: Groovy supports both static and dynamic typing, providing flexibility in type declarations. This allows developers to gradually introduce type annotations and enforce stricter typing as needed, balancing the benefits of static typing with the convenience of dynamic typing.
• Tooling and Community Support: Groovy has a thriving community and is supported by a range of tools and IDEs, including IntelliJ IDEA and Eclipse. It has extensive documentation, tutorials, and active community forums, making it easy to find resources and get support when needed.

Examples

Here's an example of a Groovy script for Jenkins that retrieves parameters from a build and triggers another build with those parameters:

def build = Jenkins.instance.getItemByFullName('YourJobName').getLastBuild() This line retrieves the last build of a Jenkins job named 'YourJobName' and assigns it to the variable 'build'.

def params = build.getAction(ParametersAction)?.parameters This line retrieves the parameters from the current build by accessing the ParametersAction associated with the 'build' variable. The parameters are then assigned to the variable 'params'. The '?.' is used for null-safe navigation, meaning if the ParametersAction is null, it won't throw an error.

This block of code defines the parameters for a new build by iterating over each parameter in the 'params' list. It uses a switch statement to customize parameter values if needed. In this example, it modifies the value of 'param1' to "Modified Value" and maps 'param2' to 'newParam2'. If a parameter doesn't match any case, it keeps the parameter unchanged. The modified or unchanged parameters are stored in the 'newBuildParams' list.

def job = Jenkins.instance.getItemByFullName('YourOtherJobName') This line retrieves a Jenkins job named 'YourOtherJobName' and assigns it to the variable 'job'.

def newBuild = job.scheduleBuild2(0, new ParametersAction(newBuildParams)) This line triggers a new build for the 'job' with the retrieved parameters. It uses the 'scheduleBuild2' method with a delay of 0 (immediate execution) and passes a new instance of the ParametersAction class with the 'newBuildParams' list as the parameter values.

println "New build triggered: ${newBuild}" Finally, this line prints a message indicating that a new build has been triggered. It includes the value of the 'newBuild' variable, which represents the newly triggered build.

Complete Code

Replace 'YourJobName' with the name of the job from which you want to retrieve parameters. Replace 'param1' and 'param2' with the names of the specific parameters you want to customize or map. Replace 'YourOtherJobName' with the name of the job to trigger the new build.

This script retrieves the parameters from the last build of a specific job, modifies or maps the parameter values if necessary, and triggers a new build with the updated parameters. The new build is scheduled using the scheduleBuild2() method, passing in the modified parameters using the ParametersAction class.