如何将对象传递给一个暴露的luaj函数？ [英] How can I pass objects to an exposed luaj function?

问题描述

我试图使用Luaj + java构建一个控制器。我有以下的java类

  public class Duck {
 public void talk（）{System.out.println 鸭acks！）; } 
 public void walk（）{System.out.println（Duck walking！ } 
} 
 
 public class Person {
 public void talk（）{System.out.println（Person talks！ } 
 public void walk（）{System.out.println（Person walks！ } 
} 
  

和以下控制器的lua脚本：

  onTalk（obj）
 obj：talk（）; 
 end 
 
 onWalk（obj）
 obj：walk（）; 
 end 
  

我希望定义一个控制器保留所有程序的逻辑，我想将API从该控制器暴露到我的java代码。我试图使用以下方法：

  ScriptEngineManager sem = new ScriptEngineManager（）; 
 ScriptEngine engine = sem.getEngineByExtension（。lua）; 
 ScriptEngineFactory factory = engine.getFactory（）; 
 
 //上面定义的脚本
 CompiledScript cs =（（Compilable）engine）.compile（MY_LUA_SCRIPT）; 
 SimpleBindings b = new SimpleBindings（）; 
 
 b = newSimpletBindings（）; 
 
 LuaValue onWalkHandler =（LuaValue）b.get（onWalk）; 
 //func.call(LuaValue.valueOf(duck））; //传递鸭子对象不工作??? 
  

我无法将对象传递给LuaValue。如何将一个java对象传递给lua脚本？

PS：一般来说，当使用Java和嵌入脚本时，人们在一个脚本中捆绑函数，

我正在搜索 luaj 条目，找到您的未回答。你的问题很有趣，让我搜索。然后我意识到，它是在2年前被问的...我希望我的答案可以对别人有用！基于luaj-3.0-alpha1的代码。

我们需要一个有效的Lua脚本（您忘记了 function 关键字） ：

  function onTalk（javaObj）
 print（type（javaObj）.. ... tostring（javaObj））
 print（javaObj.name）
 javaObj：talk（）
 return true 
 end 
 
函数onWalk ）
 javaObj：walk（）
 return 1，km
 end 
  

$ b b

我添加了一些跟踪...
我也做了类似于你的类：

  Dog 
 {
 public String name; 
 Dog（String n）{name = n; } 
 public void talk（）{System.out.println（Dog+ name +barks！ } 
 public void walk（）{System.out.println（Dog+ name +walks ...）; } 
} 
 class Cat 
 {
字符串名称; 
 Cat（String n）{name = n; } 
 public void talk（）{System.out.println（Cat+ name +meows！ } 
 public void walk（）{System.out.println（Cat+ name +walks ...）; } 
} 
  

添加一个字段进行测试。对于我的测试，我只是在方法中声明了创建他们的实例的类：

  Dog dog = new Dog（Rex） ; 
 Cat cat = new Cat（Felix）; 
 

我首先尝试使用 LuaValue luaDog = LuaValue.userdataOf（dog）; 但它不工作：我们确实有userdata，如trace所示，但没有metatable，所以我们不能调用方法或访问字段。

经过很多搜索，我发现了正确的咒语：

  CompiledScript脚本=（（Compilable）scriptEngine）.compile（阅读器）; 
 Bindings sb = new SimpleBindings（）; 
 script.eval（sb）; //将Lua函数放入sb环境
 LuaValue luaDog = CoerceJavaToLua.coerce（dog）; // Java to Lua 
 LuaFunction onTalk =（LuaFunction）sb.get（onTalk）; // Get Lua function 
 LuaValue b = onTalk.call（luaDog）; //调用函数
 System.out.println（onTalk answered：+ b）; 
 LuaFunction onWalk =（LuaFunction）sb.get（onWalk）; 
 LuaValue [] dogs = {luaDog}; 
 Varargs dist = onWalk.invoke（LuaValue.varargsOf（dogs））; // Alternative 
 System.out.println（onWalk返回：+ dist）; 
 



我欣赏Luaj API ... :-)可能更多的Java程序员，而其他库似乎以更多地瞄准Lua / C程序员...

I am trying to build a controller using Luaj + java. I have the following java classes

public class Duck {
  public void talk() { System.out.println("Duck quacks!"); }
  public void walk() { System.out.println("Duck walks!"); }
}

public class Person {
  public void talk() { System.out.println("Person talks!"); }
  public void walk() { System.out.println("Person walks!"); }
}

and the following lua script for the controller:

onTalk(obj) 
  obj:talk();
end

onWalk(obj)
   obj:walk();
end

I would ideally like to define one controller (written in lua) where I will keep all of the program's logic, and I would like to expose API from that controller to my java code. I was trying to use the following approach:

ScriptEngineManager sem     = new ScriptEngineManager();
ScriptEngine        engine  = sem.getEngineByExtension(".lua");
ScriptEngineFactory factory = engine.getFactory();

// Script defined above
CompiledScript cs = ((Compilable)engine).compile(MY_LUA_SCRIPT);
SimpleBindings b = new SimpleBindings();

b = newSimpletBindings();

LuaValue onWalkHandler = (LuaValue)b.get("onWalk");
//func.call(LuaValue.valueOf(duck)); // Passing duck object does not work ???

I am not able to pass the object to the LuaValue. How can I pass a java object to the lua script?

PS: In general, when using Java and embedded scripting, do people bundle functions in one script, or is there a separate script for every callback?

解决方案

I was searching luaj entries and found your unanswered. Your question was interesting and made me search. Then I realized that it was asked 2 years ago... I hope my answer can be useful to somebody else! Code based on luaj-3.0-alpha1.

We need a valid Lua script (you forgot the function keyword):

function onTalk(javaObj)
  print(type(javaObj) .. " " .. tostring(javaObj))
  print(javaObj.name)
  javaObj:talk()
  return true
end

function onWalk(javaObj)
  javaObj:walk()
  return 1, "km"
end

I added a bit of trace... I also made classes similar to your:

class Dog
{
  public String name;
  Dog(String n) { name = n; }
  public void talk() { System.out.println("Dog " + name + " barks!"); }
  public void walk() { System.out.println("Dog " + name + " walks..."); }
}
class Cat
{
  String name;
  Cat(String n) { name = n; }
  public void talk() { System.out.println("Cat " + name + " meows!"); }
  public void walk() { System.out.println("Cat " + name + " walks..."); }
}

Adding a field to test this too. For my test, I just declared the classes inside the method creating their instances:

Dog dog = new Dog("Rex");
Cat cat = new Cat("Felix");

I first tried to convert these Java objects to Lua, using LuaValue luaDog = LuaValue.userdataOf(dog); but it doesn't work: we indeed have userdata, as shown by the traces, but no metatable, so we cannot call the methods nor access the fields.

After searching a lot, I found out the right incantation:

CompiledScript script = ((Compilable) scriptEngine).compile(reader);
Bindings sb = new SimpleBindings();
script.eval(sb); // Put the Lua functions into the sb environment
LuaValue luaDog = CoerceJavaToLua.coerce(dog); // Java to Lua
LuaFunction onTalk = (LuaFunction) sb.get("onTalk"); // Get Lua function
LuaValue b = onTalk.call(luaDog); // Call the function
System.out.println("onTalk answered: " + b);
LuaFunction onWalk = (LuaFunction) sb.get("onWalk");
LuaValue[] dogs = { luaDog };
Varargs dist = onWalk.invoke(LuaValue.varargsOf(dogs)); // Alternative
System.out.println("onWalk returned: " + dist);

I appreciate the Luaj API... :-) Probably more made for Java programmers while other libraries seem to aim more at Lua / C programmers...

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