Java脚本教程 - Java调用Javascript函数

以下代码显示了如何从Java调用Javascript函数。

首先，它定义了Javascript文件中的四个函数并保存它到c:/Java_Dev/calculator.js。

var calculator = new Object();

calculator.add = function (n1, n2) n1 + n2;
calculator.subtract = function (n1, n2) n1 - n2;
calculator.multiply = function (n1, n2) n1 * n2;
calculator.divide = function (n1, n2) n1 / n2;

然后，使用eval()函数加载脚本并获取表示函数的Object。

String scriptPath = "c:/Java_Dev/calculator.js";
engine.eval("load("" + scriptPath + "")");
Object calculator = engine.get("calculator");

最后，通过名称获取函数并传递参数。

Object addResult = inv.invokeMethod(calculator, "add", x, y);
Object subResult = inv.invokeMethod(calculator, "subtract", x, y);
Object mulResult = inv.invokeMethod(calculator, "multiply", x, y);
Object divResult = inv.invokeMethod(calculator, "divide", x, y);

例子

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

public class Main {
  public static void main(String[] args) throws Exception {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    if (!(engine instanceof Invocable)) {
      System.out.println("Invoking methods is not supported.");
      return;
    }
    Invocable inv = (Invocable) engine;
    String scriptPath = "c:/Java_Dev/calculator.js";

    engine.eval("load("" + scriptPath + "")");

    Object calculator = engine.get("calculator");

    int x = 3;
    int y = 4;
    Object addResult = inv.invokeMethod(calculator, "add", x, y);
    Object subResult = inv.invokeMethod(calculator, "subtract", x, y);
    Object mulResult = inv.invokeMethod(calculator, "multiply", x, y);
    Object divResult = inv.invokeMethod(calculator, "divide", x, y);

    System.out.println(addResult);
    System.out.println(subResult);
    System.out.println(mulResult);
    System.out.println(divResult);
  }
}

上面的代码生成以下结果。

这里是c:/Java_Dev/calculator.js的源代码。

var calculator = new Object();

calculator.add = function (n1, n2) n1 + n2;
calculator.subtract = function (n1, n2) n1 - n2;
calculator.multiply = function (n1, n2) n1 * n2;
calculator.divide = function (n1, n2) n1 / n2;