"The mechanic that would perfect his work must first sharpen his tools."
- Confucius
The development environment consists of tools and libraries that are useful to implement, debug, and make changes to software systems. The efficiency of a development team is highly dependent on the development environment and technology stack at hand. In this chapter, you will learn how to set up a development environment for microservices using the Clojure ecosystem. This chapter will help you to:
Clojure (https://clojure.org/) is a dialect of the Lisp (https://en.wikipedia.org/wiki/Lisp_(programming_language) programming language and primarily runs on a Java virtual machine (JVM). The other target implementations include ClojureCLR (https://github.com/clojure/clojure-clr), which runs on Common Language Runtime (CLR), and ClojureScript, which compiles to JavaScript. Although Clojure uses a JVM as its underlying runtime engine, it emphasizes a functional programming language with immutability at its core. All data structures of Clojure are immutable. Since Clojure is a dialect of Lisp, it also treats code as data and is known to be homoiconic. Its syntax is built on S-expressions (https://en.wikipedia.org/wiki/S-expression) that are first parsed as a data structure and then translated into constructs of the Java programming language before being compiled into Java bytecode. Clojure also supports metaprogramming with macro (https://en.wikipedia.org/wiki/Macro_(computer_science...
Build tools are of prime importance for any programming language. They not only help to generate a deployable artifact for the application, but also manage the dependencies of the application throughout its development life cycle. Leiningen and Boot (http://boot-clj.com/) are two widely used build tools for Clojure. Since Clojure is a hosted language for JVM, Clojure build tools primarily generate JARs as deployable artifacts for all Clojure projects.
Leiningen is a build and project management tool that is written in Clojure and is widely used across Clojure projects. It describes a Clojure project using generic Clojure data structures. It integrates well with the Maven repository from the Java world and the Clojars (https://clojars.org/) repository of Clojure libraries, for dependency management and releases. Leiningen has built-in support for plugins to extend its functionality. It also provides an option to design application templates that can help create...
A Clojure project is a directory that contains source files, test files, resources, documentation, and project metadata. Source files are primarily from Clojure, but a project may contain Java source files as well. Leiningen has a default project template that can be used to quickly create a Clojure project structure using the lein new <project-name> command:
# Create a new project 'playground' % lein new playground Generating a project called playground based on the 'default' template. The default template is intended for library projects, not applications. To see other templates (app, plugin, etc), try `lein help new`. # Show the 'playground' project directory structure % tree playground playground ├── CHANGELOG.md ├── doc │ └── intro.md ├── LICENSE ├── project.clj ├── README.md ├── resources ├── src │ └── playground │ └── core.clj └── test └── playground └── core_test.clj 6 directories, 7 files
Each Clojure project contains a project metadata...
An integrated development environment (IDE) is a software application that provides utilities for programmers to develop, build, and debug software applications. It consists of a code editor, build automation tool, and a debugger. Clojure has a growing number of IDEs available, out of which Emacs (https://en.wikipedia.org/wiki/Emacs) and Vim (https://en.wikipedia.org/wiki/Vim_(text_editor)) stand out. Although this book does not cover IDEs, wherever one is referred to, uses Emacs as the IDE. Both Emacs and Vim are text editors that need additional plugins to support Clojure. Emacs needs CIDER (https://github.com/clojure-emacs/cider), whereas Vim gets REPL support using Fireplace (https://github.com/tpope/vim-fireplace).
Some other Clojure IDEs that are widely used are:
In this chapter, we focused on the development environment for the Helping Hands application. Since Clojure is our language of choice for implementation, we first looked at the history of Clojure and Lisp and understood why it is well suited for our use case. We also looked at the REPL environment and two build tools for Clojure—Leiningen and Boot. Further, we defined a reference Leiningen project configuration for our application and learned how to run an application and test it. We also learned how to generate documentation and reports, and how to create a deployable artifact. At the end, we briefly looked at the Clojure IDEs that can make our application development work easy.
In the next chapter, we will learn about REST specification. We will learn how to define REST APIs for microservices in the Helping Hands application that can help with direct messaging among the services.
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