重点：

1、jmeter中的jsr223 preprocessor中内嵌的javascript版本是ECMA 5.1,postman中可以执行的脚本（ECMA 6）,过来需要进行降级实现(ECMA 5.1)

2、jmeter压测中的number of threads(users)代表并发数,ramp-up period(seconds)代表多少秒内发起users,duration(seconds)代表持续多长时间

可被执行的javascript代码:

//加载外部资源
load("https://www.xxx.com/crypto-js-3.1.2/core.js");
load("https://www.xxx.com/crypto-js-3.1.2/hmac.js");
load("https://www.xxx.com/crypto-js-3.1.2/enc-base64.js");
load("https://www.xxx.com/crypto-js-3.1.2/sha256.js");

//加密函数
function encryptSHA256(content, secret) {
  var hmac = CryptoJS.HmacSHA256(content, secret);
  return CryptoJS.enc.Base64.stringify(hmac)
}
//随机数函数
function getNonce(len) {
  // 密码字典
  var str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  // 大写字母密码字典
  var bigStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  // 小写字母的密码字典
  var upperStr = 'abcdefghijklmnopqrstuvwxyz';
  // 数字的密码字典
  var numStr = '0123456789';
  var builder = '';
  var count = 0;
  var isContainBigChar = false;
  var isContainUpperChar = false;
  var isContainNumChar = false;
  while (count < len - 3) {
    //生成 0 ~ 密码字典-1之间的随机数
    var i = Math.floor(Math.random() * str.length);
    builder += str[i];
    count++;
    if (!isContainBigChar && bigStr.indexOf(str[i])!=-1) {
      isContainBigChar = true;
    }
    if (!isContainUpperChar && upperStr.indexOf(str[i])!=-1) {
      isContainUpperChar = true;
    }
    if (!isContainNumChar && numStr.indexOf(str[i])!=-1) {
      isContainNumChar = true;
    }
  }
  // 如果不存在的，则加，确保一定会存在数字，大写字母，小写字母
  if (!isContainBigChar) {
    builder += bigStr[Math.floor(Math.random() * bigStr.length)];
  }
  if (!isContainUpperChar) {
    builder += upperStr[Math.floor(Math.random() * upperStr.length)];
  }
  if (!isContainNumChar) {
    builder += numStr[Math.floor(Math.random() * numStr.length)];
  }
  while (builder.length < len) {
    builder += str[Math.floor(Math.random() * str.length)];
  }
  return builder;

}
//定义http头所需变量
var appKey = '350dd9d1e3fd425681df8cb1eccd4663';
var secretKey = '9fae5a9334a52718a6d9784b32857fb0e06251754f213ea04ce5cfaa8562caaa';

var timestamp = Date.now();
var nonce = getNonce(8);
//获取request内容
var sampler = ctx.getCurrentSampler ();
var args = sampler.getProperty ("HTTPsampler.Arguments");
var httpArg = args.getObjectValue ().getArguments ().get (0);
var jsonObject = httpArg.getObjectValue ().getProperty ("Argument.value").getStringValue ();

jsonObject.appKey=appKey;
jsonObject.timestamp=String(timestamp);
jsonObject.nonce=nonce;
jsonObject.xidList=JSON.stringify(jsonObject.xidList);
//5.1语法
var plainText = '';
for (x in jsonObject) {
	plainText += ''+x+'='+[x]+'&';
}
plainText = plainText.slice(0, -1);
//生成加密内容
var sign = encryptSHA256(plainText, secretKey);
//置入变量,在后续请求中使用该变量
vars.put("appKey",appKey)
vars.put("timestamp",timestamp)
vars.put("sign",sign)
vars.put("nonce",nonce)

感谢: teacher c,teacher w.