jmeter自带加密工具类DigestUtils

// md5
import org.apache.commons.codec.digest.DigestUtils; 

String str = "${appid}" + "${appkey}" + "${salt}";
String sign = DigestUtils.md5Hex(str);
vars.put("sign",sign);

// sha256
import org.apache.commons.codec.digest.DigestUtils;

String keytoSign = "需要进行加密的字符串";
String sign = DigestUtils.sha256Hex(keytoSign);
log.info("================"+sign);

vars.put("sign",sign);