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cljminecraft has two specific goals:

Open up support for other clojure plugins on Bukkit

The first objective is accomplished within the class and the cljminecraft.core namespace. It will take care of calling the [plugin].core/start function, passing in the Bukkit plugin object for local plugin state handling.

Provide convenience functions to make writing plugins more idiomatic to clojure

The second objective is accomplished by the various other namespaces in clj-minecraft. I'm keeping the structure fairly flat and concise so that one can write idiomatic code for 80% of the plugin code.




Install the mod

Download the latest server mod build from or build it yourself by cloning the repo and lein uberjar

Copy the jar into the Bukkit plugin folder and fire up your server. Once started, it should have opened a REPL port, by default on port 4005

If all you wanted was to enable clojure plugins on your server, you're done. If you want to write some code, read on.

Write some code

From now on, you will need leiningen installed - see

lein repl :connect 4005

Now you have an active connection to push code onto the server, let's try some stuff (the part before => is the REPL prompt...):

user=> (in-ns 'cljminecraft.core)
#<Namespace cljminecraft.core>

cljminecraft.core=> (ev/find-event "break")
("painting.painting-break-by-entity" "hanging.hanging-break" "painting.painting-break" "entity.entity-break-door" "hanging.hanging-break-by-entity" "player.player-item-break" "block.block-break")

;; block.block-break looks good.. lets see what we can get out of it
cljminecraft.core=> (ev/describe-event "block.block-break")
#{"setExpToDrop" "isCancelled" "getEventName" "setCancelled" "getExpToDrop" "getPlayer" "getBlock"}

;; Cool, getBlock looks like I can use it..
cljminecraft.core=> (defn mybreakfn [ev] {:msg (format "You broke a %s" (.getBlock ev))})

cljminecraft.core=> (ev/register-event @clj-plugin "block.block-break" #'mybreakfn)

;; Test breaking a block, I get a crazy message, let's make that more sane
cljminecraft.core=> (defn mybreakfn [ev] {:msg (format "You broke a %s" (.getType (.getBlock ev)))})

And that's a quick taste of interactive development.. The Rabbit hole goes rather deep :) enjoy.

Roll your own mod

Once you've got the cljminecraft mod installed on bukkit and you've played a bit with the REPL, you might want to build your own fully capable plugin:

lein new cljminecraft yourplugin

This will create a subfolder called yourplugin with the basics needed to get started, with some sample configuration in src/config.yml and the plugin.yml already setup under src/plugin.yml, ready to roll.

cd yourplugin
lein jar
cp target/*.jar /path/to/bukkit/plugins/

Start up your Bukkit server and go, by default, you'll see a message when you place a sign and there will be a command '/yourplugin.random' which does a dice roll. Very exciting stuff!

Remember to update your details in the plugin.yml and files - and very importantly, commit to github to share with the world.

Also, be sure to look at the wiki for more in-depth instructions on all the moving parts:

Time to hack away.


30 December 2012:

  • Implement a simple permissions extension for checking and setting specific permissions on players
    • This does not yet persist given player permissions across sessions
  • Added clj.permission as a command to give a player a specific permission
    • Autocompletion may need work as command lists within commands are untested.

29 December 2012:

  • Now sends a message to the player triggering an event when the event function returns {:msg "..."}
  • Fix up line function
  • Add actions enum to events.clj
  • Add is-block convenience function to items.clj for checking if a block is a certain material

27 December 2012:

  • Introduce cut-to-mark, copy-to-mark, pen-from-mark and clear-mark
  • Interface of line and empty line-to-mark - have to work out the math involved
  • Thinking about how to define a brush instead of just 'material' and 'painting?' in the context.

21 December 2012:

  • Revamp the block action definitions by introducing a 'defaction' macro
  • Introduce cut, copy, paste and fork - still buggy though, especially for larger areas

19 December 2012:

  • get-material now always returns MaterialData and never Material for consistency
    • Note that this could lead to API breaks
  • Implement the first working version of the block drawing primitives
    • Similar idea to Logo, forward x, turn-right, forward x, extrude :up x
  • Playing with more things in the repl.clj scratchpatch
    • Noticed that you can send a block change to a player without changing the world.. I'll look into building the functionality to setup a 'virtual' paint mode in the block drawing. Either for all players, a list of players or a single player. It would need to track the virtual paint unless cleared so that it can resend it to players as required.


A huge thanks to aiscott and basicsensei for their contributions to clj-minecraft!

Please feel free to fork and make pull requests if you want to contribute, I love code contributions - it makes the whole project that much more well rounded. On that note, we're desperately needing documentation, so if you're keen to contribute to the wiki, let me know.


Copyright (C) 2012 Deon Moolman

Distributed under the Eclipse Public License, the same as Clojure.


Clojure Bukkit plugin, Minecraft.



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