Java8中执行js脚本

代码中除了callJSFunctionFromFile函数，其他均转载于文章JDK1.8中如何用ScriptEngine动态执行JS

import jdk.nashorn.api.scripting.ScriptObjectMirror;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.SimpleBindings;
import java.io.FileReader;
import java.util.Map;
import java.util.TreeMap;

public class JSEngine {
    public static ScriptEngine engine;
    public static String str;

    public static void getValues() throws Exception{
        str = "  var msg='hello';          "
                + "  var number = 123;         "
                + "  var array=['A','B','C'];  "
                + "  var json={                "
                + "      'name':'pd',          "
                + "      'subjson':{           "
                + "           'subname':'spd'  "
                + "           ,'id':123        "
                + "           }                "
                + "      };                    ";
        engine.eval(str);
        str="msg+=' world';number+=5";
        System.out.println(engine.get("msg"));
        System.out.println(engine.get("number"));
        //获取数组
        ScriptObjectMirror array = (ScriptObjectMirror) engine.get("array");
        System.out.println(array.getSlot(0));

        ScriptObjectMirror json = (ScriptObjectMirror) engine.get("json");
        System.out.println(json.get("name"));

        //json嵌套
        ScriptObjectMirror subjson = (ScriptObjectMirror) json.get("subjson");
        System.out.println(subjson.get("subname"));
    }

    public static void getObject() throws Exception{
        str = "  var obj=new Object();     "
                + "  obj.info='hello world';   "
                + "  obj.getInfo=function(){   "
                + "        return this.info;   "
                + "  };                        ";
        engine.eval(str);
        ScriptObjectMirror obj = (ScriptObjectMirror) engine.get("obj");
        System.out.println(obj.get("info"));
        System.out.println(obj.get("getInfo"));
        str = "obj.getInfo()";
        System.out.println(engine.eval(str));
    }

    //给js传递变量
    public static void putValue() throws Exception{
        str = "Math.pow(a,b)";
        Map<String,Object> input = new TreeMap<>();
        input.put("a",2);
        input.put("b",8);
        System.out.println(engine.eval(str,new SimpleBindings(input)));
    }

    //调用js函数
    public static void callJSFunction() throws Exception{
        str = "function add (a, b) {return a+b; }";
        //执行js脚本定义函数
        engine.eval(str);
        Invocable invocable = (Invocable) engine;
        Object res = invocable.invokeFunction("add",new Object[]{2,3});
        System.out.println(res);

    }

    //读取js文件，执行函数;易变业务使用脚本编写，这样即使修改脚本，也不需重新部署java程序
    public static void callJSFunctionFromFile() throws Exception{
        //执行js
        while (true){
            //模拟执行期间add.js被修改
            Thread.sleep(5000);
            engine.eval(new FileReader("e:\add.js"));
            Invocable invocable = (Invocable) engine;
            Object res = invocable.invokeFunction("add",new Object[]{2,3});
            System.out.println(res);
        }
    }

    public static void main(String[] args) throws Exception{
        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
        engine = scriptEngineManager.getEngineByName("javascript");
        getValues();
        getObject();
        putValue();
        callJSFunction();
        callJSFunctionFromFile();
    }

}