Java8中执行js脚本

时间：2022-06-28 08:37:09

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();

    }

}

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