2010-06-16 01:58:14 +00:00
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# Tutorial
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For those of you new to the JVM who have never touched Ant or Maven in
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anger: don't panic. Leiningen is designed with you in mind. This
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2010-06-17 04:10:56 +00:00
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tutorial will help you get started and explain Leiningen's take on
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project building and JVM-land dependency management.
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2010-06-16 01:58:14 +00:00
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## Creating a Project
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We'll assume you've got Leiningen installed as per the
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2010-06-19 03:56:36 +00:00
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[README](http://github.com/technomancy/leiningen/blob/master/README.md).
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2010-06-16 01:58:14 +00:00
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Generating a new project is easy:
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$ lein new myproject
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Created new project in: myproject
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$ cd myproject
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$ tree
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.
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|-- project.clj
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|-- README
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|-- src
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| `-- myproject
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| `-- core.clj
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`-- test
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`-- myproject
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`-- core_test.clj
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2010-06-17 04:10:56 +00:00
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Here we've got your project's README, a src/ directory containing
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implementation code, a test/ directory, and a project.clj file which
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2010-06-16 01:58:14 +00:00
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describes your project to Leiningen. The src/myproject/core.clj file
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corresponds to the myproject.core namespace.
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Note that we use that instead of just myproject since single-segment
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namespaces are discouraged in Clojure. Also the file
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test/myproject/core_test.clj corresponds with the myproject.core-test
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namespace--you need to remember to replace dashes in namespace names
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with underscores in file names on disk since the JVM has trouble
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loading files with dashes in the name.
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## Packaging
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You can package your project up now, even though at this stage it's
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fairly useless:
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$ lein jar
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2010-06-17 04:10:56 +00:00
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Created ~/src/myproject/myproject-1.0.0-SNAPSHOT.jar
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2010-06-16 01:58:14 +00:00
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Libraries for the JVM are packaged up as .jar files, which are
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2010-06-19 03:56:36 +00:00
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basically just .zip files with a little extra JVM-specific metadata.
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They usually contain .class files (JVM bytecode) and .clj source
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files, but they can also contain other things like config
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files. Leiningen downloads them from remote Maven repositories for
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you.
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2010-06-16 01:58:14 +00:00
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## project.clj
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$ cat project.clj
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(defproject myproject "1.0.0-SNAPSHOT"
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:description "FIXME: write"
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:dependencies [[org.clojure/clojure "1.1.0"]
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[org.clojure/clojure-contrib "1.1.0"]])
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Fill in the :description with a short paragraph so that your project
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will show up in search results once you upload to Clojars (as
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described below). At some point you'll need to flesh out the README
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too, but for now let's skip ahead to setting :dependencies. Note that
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Clojure is just another dependency here. Unlike most languages, it's
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easy to swap out any version of Clojure. If you're using Clojure
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Contrib, make sure that version matches the Clojure version.
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2010-06-16 01:58:14 +00:00
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If you've got a simple pure-clojure project, you will be fine with the
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default of depending only on Clojure and Contrib, but otherwise you'll
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need to list other dependencies.
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2010-06-16 01:58:14 +00:00
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## Dependencies
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[Clojars](http://clojars.org) is the Clojure community's centralized
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jar repository, and it's where you'll find Clojure dependencies for your
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project. Each dependency even lists out the snippet you'll need to put
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in your project.clj to use it. Java libraries can be found by
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searching [Jarvana](http://jarvana.com), though you'll need to
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2010-06-22 02:21:13 +00:00
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translate their notation into Leiningen's. Maven needs its
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dependencies to be specified in XML format:
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2010-06-22 02:21:13 +00:00
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<dependency>
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<groupId>org.clojure</groupId>
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<artifactId>clojure</artifactId>
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<version>1.1.0</version>
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</dependency>
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2010-06-22 02:21:13 +00:00
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Leiningen describes packages using identifiers that look like this:
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[org.clojure/clojure "1.1.0"]
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* "org.clojure" is called the "group-id"
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* "clojure is called the "artifact-id"
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* "1.1.0" is the version of the jar file you require
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2010-06-19 03:56:36 +00:00
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If you omit the group-id, then Leiningen will use the artifact-id for
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it. This is the convention generally used for Leiningen libraries. The
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name and version at the top of the defproject form follows the same
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rules.
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Sometimes versions will end in "-SNAPSHOT". This means that it is not
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an official release but a development build. Relying on snapshot
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dependencies is discouraged but is sometimes necessary if you need bug
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fixes etc. that have not made their way into a release yet. Adding a
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snapshot dependency to your project will cause Leiningen to actively
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go seek out the latest version of the dependency once a day when you
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run <tt>lein deps</tt>, (whereas normal release versions are cached in
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the local repository) so if you have a lot of snapshots it will slow
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things down.
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Speaking of the local repository, all the dependencies you pull in
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using Leiningen or Maven get cached in $HOME/.m2/repository since
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Leiningen uses the Maven API under the covers. You can install the
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current project in the local repository with this command:
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$ lein install
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Wrote pom.xml
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[INFO] Installing myproject-1.0.0-SNAPSHOT.jar to ~/.m2/repository/myproject/myproject/1.0.0-SNAPSHOT/myproject-1.0.0-SNAPSHOT.jar
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2010-06-19 03:56:36 +00:00
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Generally Leiningen will fetch your dependencies when they're needed,
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but if you have just added a new dependency and you want to force it
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to fetch it, you can do that too:
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2010-06-16 01:58:14 +00:00
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$ lein deps
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2010-06-17 04:10:56 +00:00
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Copying 2 files to ~/src/myproject/lib
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Copied :dependencies into ~/src/myproject/lib.
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2010-06-16 01:58:14 +00:00
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Dependencies are downloaded from Clojars, the central Maven (Java)
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repository, the [official Clojure build
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server](http://build.clojure.org), and any other repositories that you
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add to your project.clj file. See :repositories in
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[sample.project.clj](http://github.com/technomancy/leiningen/blob/master/sample.project.clj).
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If you've confirmed that your project will work with a number of
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different versions of a given dependency, you can provide a range
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instead of a single version:
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[org.clojure/clojure "[1.1,1.2]"] ; <= will match 1.1.0 through 1.2.0.
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See [Maven's version range
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specification](http://maven.apache.org/plugins/maven-enforcer-plugin/rules/versionRanges.html)
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for details.
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## Dev Dependencies
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Sometimes you want to pull in dependencies that are really only for
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your convenience while developing; they aren't strictly required for
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the project to function. Leiningen calls these
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:dev-dependencies. They're listed in project.clj alongside regular
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dependencies and downloaded when you run <tt>lein deps</tt>, but they
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are not brought along when another project depends on your
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project. Using [swank-clojure](http://github.com/technomancy/swank-clojure)
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for Emacs support would be a typical example; you may not want it
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included at runtime, but it's useful while you're hacking on the project.
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## Writing the Code
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This is the part Leiningen can't really help you with; you're on your
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own here. Well--not quite. Leiningen can help you with running your
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tests.
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$ lein test
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Testing myproject.core-test
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FAIL in (replace-me) (core_test.clj:6)
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No tests have been written.
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expected: false
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actual: false
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Ran 1 tests containing 1 assertions.
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1 failures, 0 errors.
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Of course, we haven't written any tests yet, so we've just got the
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skeleton failing tests that Leiningen gave us with <tt>lein
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new</tt>. But once we fill it in the test suite will become more
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useful. Sometimes if you've got a large test suite you'll want to run
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just one or two namespaces at a time:
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$ lein test myproject.parser-test
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Testing myproject.parser-test
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Ran 2 tests containing 10 assertions.
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0 failures, 0 errors.
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## Compiling
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If you're lucky you'll be able to get away without doing any AOT
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(ahead-of-time) compilation. But there are some Java interop features
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that require it, so if you need to use them you should add an :aot
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option into your project.clj file. It should be a seq of namespaces
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you want AOT-compiled. Again, the
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[sample.project.clj](http://github.com/technomancy/leiningen/blob/master/sample.project.clj)
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has example usage.
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Like dependencies, this should happen for you automatically, but if
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you need to force it you can:
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$ lein compile
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Compiling myproject.core
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2010-06-16 01:58:14 +00:00
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## Publishing
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2010-06-17 04:10:56 +00:00
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If your project is a library and you would like others to be able to
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use it as a dependency in their projects, you will need to get it into
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a public repository. While it's possible to maintain your own or get
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it into Maven central, the easiest way is to publish it at
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[Clojars](http://clojars.org). Once you have created an account there,
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publishing is easy:
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$ lein jar && lein pom
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$ scp pom.xml myproject-1.0.0.jar clojars@clojars.org:
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Once that succeeds it will be available as a package on which other
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projects may depend. You will need to have permission to publish to
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the project's group-id under Clojars, though if that group-id doesn't
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exist yet then Clojars will automatically create it and give you
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permissions.
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Sometimes you'll need to publish libraries that you don't directly
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maintain, either because the original maintainer hasn't published it
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or because you need some bugfixes that haven't been applied upstream
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yet. In this case you don't want to publish it under its original
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group-id, since this will prevent the true maintainer from using that
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group-id once they publish it. In this case you should use
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"org.clojars.$USERNAME" as the group-id when you upload your fork.
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2010-06-16 01:58:14 +00:00
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## Uberjar
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2010-06-17 04:10:56 +00:00
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Not all Leiningen projects are libraries though--sometimes you want to
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distribute your project to end-users who don't want to worry about
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having a copy of Clojure lying around. You can use the
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<tt>uberjar</tt> task to create a standalone, executable jar.
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2010-06-17 04:19:04 +00:00
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For this to work you'll need to specify in project.clj a namespace as
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your :main that contains a <tt>-main</tt> function which will get
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called when your standalone jar is run. This namespace should have a
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<tt>(:gen-class)</tt> declaration in the <tt>ns</tt> form at the
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top. The <tt>-main</tt> function will get passed the command-line
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arguments.
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2010-06-17 04:10:56 +00:00
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$ lein uberjar
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Created ~/src/myproject/myproject-1.0.0.jar
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Including myproject-1.0.0.jar
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Including clojure-contrib-1.1.0.jar
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Including clojure-1.1.0.jar
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2010-06-17 04:19:04 +00:00
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Created myproject-1.0.0-standalone.jar
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This creates a single jar file that contains the contents of all your
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dependencies. Users can run it with a simple <tt>java</tt> invocation,
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or on some systems just by double-clicking the jar file.
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2010-06-17 04:19:04 +00:00
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$ java -jar myproject-1.0.0-standalone.jar
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## That's It!
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If you prefer a visual introduction, try the Full Disclojure
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screencast on [project management](http://vimeo.com/8934942). Now go
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start coding your next project!
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