JDK8系列之JavaScript引擎Nashorn

从JDK1.8开始，Java采用Nashorn作为嵌入式 JavaScript 引擎。JDK1.6和JDK1.7采用Rhino。Nashorn 支持 ECMAScript 5.1 规范，使用基于 JSR 292 的新语言特性，其中包含在 JDK 7 中引入的 invokedynamic，将 JavaScript 编译成 Java 字节码。

下面给出一些例子加深理解，一个最简单的例子，调用1 2，计算输出打印

代码语言：javascript复制

package com.example.jdkexample.core.nashorn;


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

public class NashornJavaScriptExample {


    public static void main(String[] args) throws ScriptException {
         ScriptEngineManager engineManager = new ScriptEngineManager();
        ScriptEngine scriptEngine = engineManager.getEngineByName("JavaScript");
        String foo = "1 2";
        System.out.println(scriptEngine.eval(foo));
        
    }
}

可以利用ScriptEngine对js进行执行，然后通过Hutool转为javabean

代码语言：javascript复制

private static void testJson() throws ScriptException {
        String script = "var json ={"name":"admin" , "mobiTel":"123"};"  
                "var result ={};result.name=json.name;result.mobiTel=json.mobiTel;JSON.stringify(result);";

        ScriptEngineManager engineManager = new ScriptEngineManager();
        ScriptEngine scriptEngine = engineManager.getEngineByName("JavaScript");
        Object obj = scriptEngine.eval(script);
        User user = JSONUtil.toBean(obj.toString() , User.class);
        System.out.println(user.toString());
    }

读取js文件，然后执行js脚本

代码语言：javascript复制

private static void testJsFile()  {
        try (Reader reader= new FileReader(new File(ScriptEngineExample.class.getClassLoader().getResource("test.js").getFile()))){
            ScriptEngineManager engineManager = new ScriptEngineManager();
            ScriptEngine scriptEngine = engineManager.getEngineByName("JavaScript");
            scriptEngine.eval(reader);
        } catch (FileNotFoundException e) {
            log.error("FileNotFoundException：{}" , e);
        } catch (IOException e) {
            log.error("IOException：{}" , e);
        } catch (ScriptException e){
            log.error("ScriptException：{}" , e);
        }
    }

给出一串js，invokeFunction调用js里的函数

代码语言：javascript复制

private static void testInvokeFunction() throws ScriptException, NoSuchMethodException {
        String script = "var json ={"name":"admin" , "mobiTel":"123"};"  
                "function jsonStringify(){ var result ={};result.name=json.name;result.mobiTel=json.mobiTel;print(JSON.stringify(result));}";
        ScriptEngineManager engineManager = new ScriptEngineManager();
        ScriptEngine scriptEngine = engineManager.getEngineByName("JavaScript");
        scriptEngine.eval(script);
        Invocable invocable = (Invocable) scriptEngine;
        invocable.invokeFunction("jsonStringify");
    }

使用Bindings 传参

代码语言：javascript复制

private static void testBinding() throws ScriptException, NoSuchMethodException {
       ScriptEngineManager engineManager = new ScriptEngineManager();
       ScriptEngine scriptEngine = engineManager.getEngineByName("JavaScript");
       Bindings bindings = new SimpleBindings();
       bindings.put("username","admin");
       scriptEngine.eval("print('hello , '   username);" , bindings);
   }

jdk javascript java

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