Using user scripts for NPC AI in java

Question

For my WIP game (or maybe future games) i think about adding custom, user written scripts for the enemie/NPC AI. Doing this any user, who knows how to write scripts can write AIs for the enemies. I want to use LUA (or other scripts if it is easier), but i have really no idea how i can:

1. Embed LUA and other scripting languages in java code
2. Let this scripts control a specific NPC or type of NPC
3. Have special functions in the scripting language to control if the player is near to NPC or similar things.

Computercraft mod for Minecraft is a good example for what i want to achieve (more or less). Just instead of executing exact commands (go 1 tile foreward go 2 tiles left etc.) i want to use the script for AI. Have you any tutorial, advice or something like that?

Answer 1

http://sourceforge.net/projects/luaj/

Here's a readme for you to go through.

Basically what you want at certain points in your code invoke Lua scripts that can perform AI calculations and spit out the result back to your Java engine. Of course, this all depends on your engine, how flexible it is in terms of possible integration, etc.

EDIT:

You need to give those scripts some context, that is setup Lua environment so that it's aware of your engine (objects/tables, functions). For example, if you want to enable users to move AI character, then you have to register (for instance) an AIEnemy object in Lua, give it some methods (move, shoot), etc. These methods then link (call) to equivalent methods in your Java engine and pass appropriate parameters.

Embedding Lua and making your app work with it is a real fun, though I've never done it in Java (C/C++).

Having said that, it requires some serious thought into design of the integration. Experiment with really simple stuff to get the feel of it, best even outside your game development. Once you get it, move forward to more serious integration.

Just as a sidenote. Don't let Lua simplicity fool you. It is a very powerful language.