从 Java 8 Nashorn 引擎运行“Graphviz”viz.js

Question

我正在尝试从服务器上的 Java 8（Nashorn 引擎）渲染 graphviz，但出现错误：

Exception in thread "main" javax.script.ScriptException: ReferenceError: "Promise" is not defined in <eval> at line number 120
    at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:455)
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:387)
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeMethod(NashornScriptEngine.java:196)
    at test1.VizDemo.main(VizDemo.java:24)
Caused by: <eval>:120 ReferenceError: "Promise" is not defined

到目前为止，这是我的（简单）程序：

import java.io.InputStreamReader;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class VizDemo {

  public static void main(String args[]) throws Exception {

    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");

    engine.eval(new InputStreamReader(VizDemo.class.getResourceAsStream(
      "./viz.js")));
    engine.eval(new InputStreamReader(VizDemo.class.getResourceAsStream(
      "./full.render.js")));

    Object v = engine.eval("new Viz();");
    System.out.println("v=" + v);

    if (engine instanceof Invocable) {
      Invocable invEngine = (Invocable) engine;
      Object result = invEngine.invokeMethod(v, "renderSVGElement",
          "digraph { a -> b; a -> c; }");
      System.out.println("result=" + result);
    }
  }

}

我错过了什么？或者……真的可以在 Java 8 中运行 Javascript 吗？

Answer 1

Nashorn 不支持Promise，你需要实现一个“Pollyfill”来提供Promise 支持。这是一个实现：https://github.com/shendepu/nashorn-polyfill