I have found the answer after looking at the luaj implementation of Lua library.
i modified my code :
package some_package;
public class aif extends OneArgFunction{
public aif() {
}
@Override
public LuaValue call(LuaValue env) {
Globals globals = env.checkglobals();
LuaTable aif = new LuaTable();
aif.set("foo", new foo());
env.set("aif", aif);
globals.package_.loaded.set("aif", aif);
return aif;
}
//the rest contains the implementations of java functions
}
I code the aif class to TwoArgFunction is because the tutorial said to do so. Now with the above code, no need to require the class in lua file