Creating a new project

Leiningen can help us create a new project using templates, there is a wide variety of templates available and you can build and distribute your own in Maven.

Some of the most common types of templates are:

• Creating a jar library (the default template)
• Creating a command-line app
• Creating a Clojure web app

Let's create a new Clojure command-line app and run it:

lein new app getting-started
cd getting-started
lein run
# Hello, world!

Project structure

Leiningen is similar to other Java development tools; it uses a similar convention and allows for heavy customizations in the project.clj file.

If you are familiar with Maven or Gradle, you can think of it as pom.xml or build.gradle respectively.

The following screenshot is the project structure:

As you can see in the preceding screenshot, there are four main folders:

• resources: It holds everything that should be in the class path, such as files, images, configuration files, properties files, and other resources needed at runtime.
• src: Your Clojure source files; they are ordered in a very similar fashion to the classpath.
• dev-resources: Everything that should be in the classpath in development (when you are running Leiningen). You can override your "production" files here and add files that are needed for tests to run.
• test: Your tests; this code doesn't get packaged but it is run every time you execute the Leiningen test.

Creating a standalone app

Once your project is created, you can build and run a Java standalone command-line app quite easily, let's try it now:

lein uberjar
java -jar target/uberjar/getting-started-0.1.0-SNAPSHOT-standalone.jar
# Hello, World!

As you can see, it is quite easy to create a standalone app and it is very similar to using Maven or Gradle.