Java中运行javascript代码

时间：2021-09-08 14:59:44

原文作者：russle

原文地址：Java中运行javascript代码(二)

1、Java 代码

第一个示例，通过java将json对象传递给js函数

第二个示例， 将数组传递给js函数，js需要将其中个别位置的字节数组组合后再转回为10进制。

例如，将数组第5和6位，转变为数字， 0xa1, 0x9F, 也就是线组成a19f,然后转换41375。

package com.yq.jsdemo;

import com.alibaba.fastjson.JSONObject;

import lombok.extern.slf4j.Slf4j;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import java.io.File;

import java.io.Reader;

import java.nio.charset.Charset;

import java.nio.file.Files;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

/**

 * Simple to Introduction

 * className: JavaJSDemo

 *

 * @author EricYang

 * @version 2018/12/22 9:51

 */

@Slf4j

public class JavaJSListDemo {

    private static final String JS_ENGINE_NAME= "nashorn";

    private final ScriptEngineManager sem = new ScriptEngineManager();

    private final ScriptEngine engine = sem.getEngineByName(JS_ENGINE_NAME);

    public static void main(String[] args) {

        JavaJSListDemo demo = new JavaJSListDemo();

        demo.invokeFunctionByFileWithParams();

        demo.invokeFunctionByFileWithListParams();

    }

    private void invokeFunctionByFileWithParams() {

        log.info("---          invokeFunctionWithParams         ---" );

        try {

            log.info("Current dir={}", System.getProperty("user.dir"));

            File file = new File("./javademo/src/main/resources/demoWithParams.js");

            Reader reader = Files.newBufferedReader(file.toPath(), Charset.defaultCharset());

            Object obj1 = engine.eval(reader);

            Invocable jsInvoke = (Invocable) engine;

            JSONObject user = new JSONObject();

            user.put("name", "张三");

            user.put("age", 18);

            //js函数的就是去user对象age然后加上3

            Object obj2 = jsInvoke.invokeFunction("myFunc", user,3);

            log.info("function={}, result={}", obj1, obj2);

        }

        catch(Exception ex) {

            log.warn("exception", ex);

        }

    }

    private void invokeFunctionByFileWithListParams() {

        log.info("---         With List Params         ---" );

        try {

            log.info("Current dir={}", System.getProperty("user.dir"));

            File file = new File("./javademo/src/main/resources/demoWithListParams.js");

            Reader reader = Files.newBufferedReader(file.toPath(), Charset.defaultCharset());

            Object obj1 = engine.eval(reader);

            Invocable jsInvoke = (Invocable) engine;

            List<Short> dataList = new ArrayList<>();

            //15,01,00,00,00,0x0B,01,03,08,01,83,0x63,0x88,02,03,0xEA,0x1B

            dataList.add((short)0x15);

            dataList.add((short)0x01);

            dataList.add((short)0x00);

            dataList.add((short)0x00);

            dataList.add((short)0x00);

            dataList.add((short)0x0B);

            dataList.add((short)0x01);

            dataList.add((short)0x03);

            dataList.add((short)0x08);

            dataList.add((short)0x01);

            dataList.add((short)0x83);

            dataList.add((short)0x63);

            dataList.add((short)0x88);

            dataList.add((short)0x02);

            dataList.add((short)0x03);

            dataList.add((short)0xEA);

            dataList.add((short)0x1B);

            Object obj2 = jsInvoke.invokeFunction("myFunc", Arrays.toString(dataList.toArray()), "device1234");

            log.info("function={}", obj1);

            log.info("result={}", obj2);

        }

        catch(Exception ex) {

            log.warn("exception", ex);

        }

    }

}

2、JS代码

2.1demoWithParams.js

传入的user是个json对象， 将user的age属性加上inc然后返回。

function myFunc( user, inc) {

   return user.age + inc ;

}

2.2demoWithListParams.js

传入的对象是个数组， 类似"[0x83,0x63,0x88,0x02,0x03,0xEA,0x1B]"。

function myFunc(msgStr, deviceIdStr) {

    var scriptInput = JSON.parse(msgStr);

   	var temperature = scriptInput.slice(9, 13);

   	var fullTempValArray = temperature.slice(2, 4);

   	var strArrayTemp = [];

   	for(var i=0; i<2; i++) {

   		strArrayTemp.push(fullTempValArray[i].toString(16));

   	}

   	//console.log("fullTempValArray:", fullTempValArray, ", strArrayTemp:", strArrayTemp.join(''));

   	var tempVal = parseInt(strArrayTemp.join(''), 16);

   	var decimalsNumArray = temperature.slice(1, 2);

   	//tempVal是显示的值，实际值需要根据decimalsNumArray 进行处理， 这里的处理规则是如果decimalsNumArray 减去128的数字，作为小数位数。 也就是tempVal需要除以多少，例如当decimalsNum等4， tempVal需要除以10000，保留4位小数

   	var decimalsNum = parseInt(decimalsNumArray.join('')) -128;

   	var actualTempValue = Number((tempVal / (Math.pow(10, decimalsNum))).toFixed(decimalsNum));

   	//console.log(actualTempValue)

   	var humidity = scriptInput.slice(13, 17);

   	//console.log("-humidity--");

   	//console.log(humidity);

   	var fullHumiValArray = humidity.slice(2, 4);

   	var humiVal = parseInt(fullHumiValArray.join(''), 16);

   	var strArrayHumi = [];

   	for(var i=0; i<2; i++) {

   		strArrayHumi.push(fullHumiValArray[i].toString(16));

   	}

    humiVal = parseInt(strArrayHumi.join(''), 16);

   	//console.log("fullHumiValArray", fullHumiValArray, fullHumiValArray.join(''), " new:", humiVal)

   	//console.log("humiVal", humiVal)

   	decimalsNumArray = humidity.slice(1, 2);

   	decimalsNum = parseInt(decimalsNumArray.join('')) % 10;

   	var actualHumiValue = Number((humiVal / (Math.pow(10, decimalsNum))).toFixed(decimalsNum));

   	//console.log(actualHumiValue);

   	var data = {}

   	data.temperature = actualTempValue;

   	data.humidity = actualHumiValue;

   	data.deviceId = deviceIdStr;

    return JSON.stringify(data);

}

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