Setting Up the Clojure Environment for Java Developers

11.3.2 Setting Up the Clojure Environment

Transitioning from Java to Clojure involves setting up a robust development environment that leverages the strengths of both languages. In this section, we’ll guide you through the process of setting up a Clojure environment tailored for Java developers. We’ll cover the installation of necessary tools, integration of Clojure build tools into your workflow, and setting up continuous integration and deployment pipelines.

Understanding the Clojure Ecosystem

Before diving into the setup, it’s important to understand the core components of the Clojure ecosystem:

• Clojure: A functional programming language that runs on the Java Virtual Machine (JVM), offering seamless Java interoperability.
• Leiningen: A popular build automation tool for Clojure, similar to Maven in Java.
• tools.deps: A dependency management tool that provides a more flexible approach compared to Leiningen.
• REPL (Read-Eval-Print Loop): An interactive programming environment that allows for rapid experimentation and development.

Installing Clojure

Prerequisites

Ensure that you have Java installed on your system, as Clojure runs on the JVM. You can verify your Java installation by running:

java -version

If Java is not installed, refer to Chapter 2.1: Installing Java for detailed instructions.

Installing Clojure on Windows, macOS, and Linux

Clojure can be installed using the Clojure CLI tools, which provide a straightforward way to manage dependencies and run Clojure programs.

1. Windows:

   • Download the Windows installer from the Clojure website.
   • Run the installer and follow the on-screen instructions.

2. macOS:

   • Use Homebrew to install Clojure:

     brew install clojure/tools/clojure
     

3. Linux:

   • Use your package manager or download the script from the Clojure website:

     curl -O https://download.clojure.org/install/linux-install-1.10.3.1029.sh
     chmod +x linux-install-1.10.3.1029.sh
     sudo ./linux-install-1.10.3.1029.sh
     

Verifying the Installation

After installation, verify that Clojure is installed correctly by running:

clojure -M -e "(println 'Hello, Clojure!)"

You should see the output Hello, Clojure!.

Integrating Build Tools

Clojure offers two primary build tools: Leiningen and tools.deps. Each has its strengths, and your choice may depend on your project’s requirements.

Leiningen

Leiningen is akin to Maven for Java developers, providing a comprehensive suite of features for managing Clojure projects.

• Installation:

  • Download the lein script and place it in your PATH.
  • Run lein in your terminal to download the necessary dependencies.

• Creating a Project:

  lein new app my-clojure-app
  

• Project Structure:

  • project.clj: Configuration file for dependencies and build settings.
  • src/: Directory for source code.
  • test/: Directory for test code.

tools.deps

tools.deps offers a more flexible approach to dependency management, allowing for fine-grained control over dependencies.

• Creating a Project:

  • Create a deps.edn file in your project directory.

• Example deps.edn:

  {:deps {org.clojure/clojure {:mvn/version "1.10.3"}}}
  

• Running a Project:

  clojure -M -m my-clojure-app.core
  

Comparing Leiningen and tools.deps

Setting Up Continuous Integration and Deployment

Continuous Integration (CI) and Continuous Deployment (CD) are crucial for maintaining code quality and ensuring seamless deployment processes.

CI/CD Tools

• GitHub Actions: Integrates directly with GitHub repositories, offering a wide range of pre-built actions for Clojure.
• Travis CI: A popular CI service that supports Clojure out of the box.
• Jenkins: Highly customizable and can be configured to build and test Clojure projects.

Example CI Configuration with GitHub Actions

Create a .github/workflows/ci.yml file in your repository:

name: Clojure CI

on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2
    - name: Set up JDK 11
      uses: actions/setup-java@v2
      with:
        java-version: '11'
    - name: Install Clojure
      run: sudo apt-get install -y clojure
    - name: Run tests
      run: lein test

This configuration sets up a CI pipeline that runs tests on every push and pull request.

Try It Yourself

Experiment with the following tasks to deepen your understanding:

• Modify the deps.edn file to include additional libraries and observe how the project behaves.
• Set up a simple CI pipeline using Travis CI and compare it with GitHub Actions.
• Create a new Clojure project using both Leiningen and tools.deps, and note the differences in setup and execution.

Summary and Key Takeaways

Setting up a Clojure environment involves installing the necessary tools, choosing the right build tool, and integrating CI/CD pipelines. By leveraging your Java knowledge, you can smoothly transition to Clojure and take advantage of its functional programming paradigm. Remember to experiment with different configurations and tools to find the setup that best suits your workflow.

Further Reading

• Official Clojure Documentation
• Leiningen Documentation
• tools.deps Guide

Exercises

1. Set up a new Clojure project using Leiningen and add a dependency for ring/ring-core.
2. Create a deps.edn file for a project and add a dependency for compojure.
3. Configure a GitHub Actions workflow to build and test a Clojure project.
4. Compare the performance of a simple Clojure application using both Leiningen and tools.deps.

Quiz Time!