java - Nashorn 脚本引擎。如何将 "org"对象从全局范围共享到局部范围？

Question

Nashorn 脚本引擎不共享从全局范围到引擎范围的“com”和“org”对象/命名空间。因为“com”和“org”是引擎提供的Java包。

在示例中，我将 a 和 org 变量放入 engine2 的全局范围。

• a = 3 已共享
• org = 10 存在于 GLOBAL_SCOPE 中，但未共享到 ENGINE_SCOPE

代码:

public static void main(String[] args) throws ScriptException {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    Bindings bindings = engine.createBindings();
    bindings.put("a", 3);
    bindings.put("org", 10);
    log("bingings-org", bindings.get("org"));
    manager.setBindings(bindings);

    ScriptEngine engine2 = manager.getEngineByName("JavaScript");
    log("global-a", engine2.getBindings(ScriptContext.GLOBAL_SCOPE).get("a"));
    log("local-a", engine2.get("a"));
    log("global-org", engine2.getBindings(ScriptContext.GLOBAL_SCOPE).get("org"));
    log("local-org", engine2.get("org"));
}

1. 有没有办法将“org”和“com”包从全局范围共享到本地范围？
2. 是否存在描述情况的文档？

Answer 1

搜索脚本全局变量时，搜索顺序是先ENGINE_SCOPE，然后GLOBAL_SCOPE。 Nashorn 引擎的 ENGINE_SCOPE 绑定(bind)是包装为 javax.script.Bindings 对象的 ECMAScript“全局”对象。正如您所观察到的，ENGINE_SCOPE 具有“org”、“com”等的映射 - 它们是 Java 包前缀对象。因此，这些将从 GLOBAL_SCOPE 绑定(bind)中隐藏任何“org”、“com”等。两种解决方案:

1. 您有向脚本公开的“上下文”变量。因此，您可以使用相同的方法来获取 GLOBAL_SCOPE 映射。

   private static void log(String msg, Object obj) {
       System.out.println(msg + " " + obj);
   }
   
   public static void main(String[] args) throws ScriptException {
       ScriptEngineManager manager = new ScriptEngineManager();
       Bindings bindings = new SimpleBindings();
       bindings.put("a", 3);
       bindings.put("org", 10);
       log("bingings-org", bindings.get("org"));
       manager.setBindings(bindings);
   
       ScriptEngine engine = manager.getEngineByName("JavaScript");
       log("global-a", engine.getBindings(ScriptContext.GLOBAL_SCOPE).get("a"));
       log("local-a", engine.get("a"));
       log("global-org", engine.getBindings(ScriptContext.GLOBAL_SCOPE).get("org"));
       log("local-org", engine.get("org"));
   
       // Use "context" to access GLOBAL_SCOPE "org" from script
       engine.eval(
           "var GLOBAL_SCOPE = javax.script.ScriptContext.GLOBAL_SCOPE;\n" +
           "var g = context.getBindings(GLOBAL_SCOPE);\n" +
           "print(g.get('org'))"); 
   }
   

2. 您可以删除 ENGINE_SCOPE 绑定(bind)中的“org”、“com”等。

   private static void log(String msg, Object obj) {
       System.out.println(msg + " " + obj);
   }
   
   public static void main(String[] args) throws ScriptException {
       ScriptEngineManager manager = new ScriptEngineManager();
       Bindings bindings = new SimpleBindings();
       bindings.put("a", 3);
       bindings.put("org", 10);
       log("bingings-org", bindings.get("org"));
       manager.setBindings(bindings);
   
       ScriptEngine engine = manager.getEngineByName("JavaScript");
       log("global-a", engine.getBindings(ScriptContext.GLOBAL_SCOPE).get("a"));
       log("local-a", engine.get("a"));
       log("global-org", engine.getBindings(ScriptContext.GLOBAL_SCOPE).get("org"));
       log("local-org", engine.get("org"));
       // "org" in ENGINE_SCOPE hides GLOBAL_SCOPE "org".
       // delete the "org" in ENGINE_SCOPE
       // you could delete "org" from Java code as well using
       // "remove" method of Bindings object
       engine.eval("delete org");
       System.out.println("after deleting ENGINE_SCOPE org");
       log("local-org", engine.get("org"));
   }