将 java class 放入 nashorn 的全局范围

Question

我这样使用沙盒 Nashorn：

ScriptEngine engine = new NashornScriptEngineFactory().getScriptEngine(
            new String[]{"--no-java", "--no-syntax-extensions", "--optimistic-types=true", "--language=es6"},
            null);

但我想在我的 javascript 中使用一个特定的 class。怎么做？例如，我有一个 class:

class MyClass
{
    public void m1()
    {
        System.out.println("This is m1");
    }
    public void m2()
    {
        System.out.println("This is m2");
    }
}

我想在脚本中使用它，比如

let a=new MyClass();
a.m1();
a.m2();

怎么做？谢谢

Answer 1

您可以使用 Bindings 向 ScriptEngine 提供 java 个对象：

import jdk.nashorn.api.scripting.NashornScriptEngineFactory;

import javax.script.Bindings;
import javax.script.ScriptEngine;
import javax.script.ScriptException;


public class MyClass {
    public static void main(String[] args) {

     ScriptEngine engine = new NashornScriptEngineFactory().getScriptEngine(
            new String[]{"--no-java", "--no-syntax-extensions", "--optimistic-types=true", "--language=es6"},
            null);

    Bindings bindings = engine.createBindings();
    bindings.put("myclass", new MyClass());
    engine.setBindings(bindings, ScriptContext.GLOBAL_SCOPE);

    String code = "myclass.m1();";

    try {
        engine.eval(code, bindings);
    } catch (ScriptException e) {
        e.printStackTrace();
    }
    }

    public void m1() {
        System.out.println("This is m1");
    }

    public void m2(String str) {
        System.out.println("This is m2 " + str);
    }

    public void m3(Class claz) {
        System.out.println(claz);
    }

}

或者如果 MyClass 确实需要在 JS 代码中实例化，你可以这样做 (works with Java >=9):

    Bindings bindings = engine.createBindings();
    bindings.put("myclass", StaticClass.forClass(MyClass.class));

    var code = "var a = new myclass(); a.m1();";

    try {
        engine.eval(code, bindings);
    } catch (ScriptException e) {
        e.printStackTrace();
    }

将 java class 放入 nashorn 的全局范围

Put java class to nashorn's global scope

java

nashorn