# Supported tags and respective `Dockerfile` links

-	[`latest`, `lein-2.5.3` (*Dockerfile*)](https://github.com/Quantisan/docker-clojure/blob/a22cdfcdf10fd5c99fa4bb993c71847ab00ee2a9/Dockerfile)
-	[`onbuild`, `lein-2.5.3-onbuild` (*onbuild/Dockerfile*)](https://github.com/Quantisan/docker-clojure/blob/a22cdfcdf10fd5c99fa4bb993c71847ab00ee2a9/onbuild/Dockerfile)

For more information about this image and its history, please see [the relevant manifest file (`library/clojure`)](https://github.com/docker-library/official-images/blob/master/library/clojure). This image is updated via pull requests to [the `docker-library/official-images` GitHub repo](https://github.com/docker-library/official-images).

For detailed information about the virtual/transfer sizes and individual layers of each of the above supported tags, please see [the `clojure/tag-details.md` file](https://github.com/docker-library/docs/blob/master/clojure/tag-details.md) in [the `docker-library/docs` GitHub repo](https://github.com/docker-library/docs).

# What is Clojure?

Clojure is a dialect of the Lisp programming language. It is a general-purpose programming language with an emphasis on functional programming. It runs on the Java Virtual Machine, Common Language Runtime, and JavaScript engines. Like other Lisps, Clojure treats code as data and has a macro system.

> [wikipedia.org/wiki/Clojure](http://en.wikipedia.org/wiki/Clojure)

![logo](https://raw.githubusercontent.com/docker-library/docs/665526c3b12cedfd721234cedb61e8433f73b75a/clojure/logo.png)

# How to use this image

## Start a Lein/Clojure instance in your app

Since the most common way to use Clojure is in conjunction with [Leiningen (`lein`)](http://leiningen.org/), this image assumes that's how you'll be working. The most straightforward way to use this image is to add a `Dockerfile` to an existing Leiningen/Clojure project:

```dockerfile
FROM clojure
COPY . /usr/src/app
WORKDIR /usr/src/app
CMD ["lein", "run"]
```

Then, run these commands to build and run the image:

```console
$ docker build -t my-clojure-app .
$ docker run -it --rm --name my-running-app my-clojure-app
```

While the above is the most straightforward example of a `Dockerfile`, it does have some drawbacks. The `lein run` command will download your dependencies, compile the project, and then run it. That's a lot of work, all of which you may not want done every time you run the image. To get around this, you can download the dependencies and compile the project ahead of time. This will significantly reduce startup time when you run your image.

```dockerfile
FROM clojure
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY project.clj /usr/src/app/
RUN lein deps
COPY . /usr/src/app
RUN mv "$(lein uberjar | sed -n 's/^Created \(.*standalone\.jar\)/\1/p')" app-standalone.jar
CMD ["java", "-jar", "app-standalone.jar"]
```

Writing the `Dockerfile` this way will download the dependencies (and cache them, so they are only re-downloaded when the dependencies change) and then compile them into a standalone jar ahead of time rather than each time the image is run.

You can then build and run the image as above.

## Compile your Lein/Clojure project into a jar from within the container

If you have an existing Lein/Clojure project, it's fairly straightforward to compile your project into a jar from a container:

```console
$ docker run -it --rm -v "$PWD":/usr/src/app -w /usr/src/app clojure lein uberjar
```

This will build your project into a jar file located in your project's `target/uberjar` directory.

# Image Variants

The `clojure` images come in many flavors, each designed for a specific use case.

## `clojure:<version>`

This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of.

## `clojure:onbuild`

This image makes building derivative images easier. For most use cases, creating a `Dockerfile` in the base of your project directory with the line `FROM clojure:onbuild` will be enough to create a stand-alone image for your project.

While the `onbuild` variant is really useful for "getting off the ground running" (zero to Dockerized in a short period of time), it's not recommended for long-term usage within a project due to the lack of control over *when* the `ONBUILD` triggers fire (see also [`docker/docker#5714`](https://github.com/docker/docker/issues/5714), [`docker/docker#8240`](https://github.com/docker/docker/issues/8240), [`docker/docker#11917`](https://github.com/docker/docker/issues/11917)).

Once you've got a handle on how your project functions within Docker, you'll probably want to adjust your `Dockerfile` to inherit from a non-`onbuild` variant and copy the commands from the `onbuild` variant `Dockerfile` (moving the `ONBUILD` lines to the end and removing the `ONBUILD` keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your `Dockerfile` as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-`ONBUILD` steps).

# License

View [license information](http://clojure.org/license) for the software contained in this image.

# Supported Docker versions

This image is officially supported on Docker version 1.9.1.

Support for older versions (down to 1.6) is provided on a best-effort basis.

Please see [the Docker installation documentation](https://docs.docker.com/installation/) for details on how to upgrade your Docker daemon.

# User Feedback

## Documentation

Documentation for this image is stored in the [`clojure/` directory](https://github.com/docker-library/docs/tree/master/clojure) of the [`docker-library/docs` GitHub repo](https://github.com/docker-library/docs). Be sure to familiarize yourself with the [repository's `README.md` file](https://github.com/docker-library/docs/blob/master/README.md) before attempting a pull request.

## Issues

If you have any problems with or questions about this image, please contact us through a [GitHub issue](https://github.com/Quantisan/docker-clojure/issues).

You can also reach many of the official image maintainers via the `#docker-library` IRC channel on [Freenode](https://freenode.net).

## Contributing

You are invited to contribute new features, fixes, or updates, large or small; we are always thrilled to receive pull requests, and do our best to process them as fast as we can.

Before you start to code, we recommend discussing your plans through a [GitHub issue](https://github.com/Quantisan/docker-clojure/issues), especially for more ambitious contributions. This gives other contributors a chance to point you in the right direction, give you feedback on your design, and help you find out if someone else is working on the same thing.
