向Nashorn脚本提供JavaScript日期 [英] Supply JavaScript date to Nashorn script

问题描述

我正在研究Java中的API，该API允许用户编写脚本并访问Nashorn脚本引擎传入的一组特定方法（以API对象的形式）。

I am working on an API in Java that allows users to write scripts and access a specific set of methods that are passed in (in the form of an API object) by the Nashorn script engine.

我想在JavaScript中调用函数getDate（），该函数将返回Java端提供的一些任意日期（作为本机JavaScript日期）。

I want to, in the JavaScript, call a function getDate(), which will return some arbitrary date (as a native JavaScript date) that's provided from the Java side.

我曾尝试将org.java.util.Date放在API对象上，但这不会像JS日期那样。目标是使具有JS经验的最终用户尽可能地简化此操作。

I have tried simply putting an org.java.util.Date on the API object, but that won't behave like a JS date. The goal is to make this as simple as possible for end-users who are experienced with JS.

Java示例：

public class MyAPI {
    public void log(String text){
        System.out.println(text);
    }

    public Date getDate(){
        // Return something that converts to a native-JS date
    }

    public static void main(){
        // MyClassFilter implements Nashorn's ClassFilter
        ScriptEngine engine = new NashornScriptEngineFactory().getScriptEngine(new MyClassFilter());
        ((Invokable) engine).invokeFunction("entryPoint", new MyAPI());
    }

JavaScript示例

JavaScript example

function entryPoint(myApi){
    var date = myApi.getDate();
    myApi.log(date.getMinutes());
}

推荐答案

Nashorn引擎具有对象在内部使用，它们表示Javascript对象。如您所料， java.util.Date！= new Date（）（在javascript中）。引擎使用名为 jdk.nashorn.internal.objects.NativeDate 的类表示其JS日期。

The Nashorn engine has objects it uses internally which represent the Javascript objects. As you have guessed the java.util.Date != new Date() (in javascript). The engine uses a class called jdk.nashorn.internal.objects.NativeDate to represent its JS date.

如果我要进行构建，则不会在Java中构建 NativeDate ，而是在其中使用包装器 MyApi 对象的Javascript，其中将包含其他一些本机JS方法，例如 getDate（）。

If I were building this out I would not have the NativeDate constructed in the Java but instead have a wrapper in Javascript for the MyApi object which would contain a few other native JS methods, such as getDate().

var MYAPI_JAVASCRIPT = {
    log: function() {
        print(arguments);
    },
    getDate: function() {
        return new Date();
    }
}

然后可以将该对象作为方法参数传递。

You could then pass that object as the method parameter.

但是，如果您确实打算在自己的计算机上使用 NativeDate 然后，您可以像这样构造Java代码：

However if your really set on using the NativeDate in your Java code then you can construct one like so:

public NativeDate getDate() {
    return (NativeDate) NativeDate.construct(true, null);
}

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