Java脚本教程 - Java脚本实现接口

在脚本中实现Java接口

Java Scripting API允许我们以脚本语言实现Java接口。

例子

假设我们想在Javascript中实现下面的Java接口。

public interface Calculator {
   double add (double n1, double n2);
}

cal.js文件的内容，保存在c:/Java_dev/cal.js下

function add(n1, n2) {
  n1 + n2;
}

从Java代码调用JavaScript中实现的Java接口。

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


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("Interface implementation in script"
          + "is not supported.");
      return;
    }
    Invocable inv = (Invocable) engine;
    String scriptPath = "c:/Java_Dev/cal.js";
    engine.eval("load("" + scriptPath + "")");
    Calculator calc = inv.getInterface(Calculator.class);
    if (calc == null) {
      System.err.println("Calculator interface "
          + "implementation not found.");
      return;
    }
    double x = 2.0;
    double y = 1.0;
    double addResult = calc.add(x, y);

    System.out.println(addResult);
  }
}