語言包含：
Javascript ，PHP，Java，Groovy，C#，Objective C，Go，Ruby，Python，Perl，Dart，Swift，Rust，Powershell。

1. Javascript HMAC SHA256

Run the code online with this jsfiddle. Dependent upon an open source js library calledhttp://code.google.com/p/crypto-js/.

<script src="http://crypto-js.googlecode.com/svn/tags/3.0.2/build/rollups/hmac-sha256.js"
 
></script>
<script src="http://crypto-js.googlecode.com/svn/tags/3.0.2/build/components/enc-base64-min.js"></script>

<script>
  var hash = CryptoJS.HmacSHA256("Message", "secret");
  var hashInBase64 = CryptoJS.enc.Base64.stringify(hash);
  document.write(hashInBase64);
</script>
 

2. PHP HMAC SHA256

PHP has built ) and base64_encode (PHP , PHP ) resulting in no outside dependencies. Say what you want about PHP but they have the cleanest code for this example.

$s = hash_hmac('sha256', 'Message', 'secret', true);
echo base64_encode($s);

3. Java HMAC SHA256

Dependent on Apache Commons Codec to encode in
 
 base64.

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;

public class ApiSecurityExample {
  public static void main(String[] args) {
    try {
     String secret = "secret";
     String message = "Message";

     Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
     SecretKeySpec secret_key = new SecretKeySpec(secret.getBytes(), "HmacSHA256");
     sha256_HMAC.init(secret_key);

     String hash = Base64.encodeBase64String(sha256_HMAC.doFinal(message.getBytes()));
     System.out.println(hash);
    }
    catch (Exception e){
     System.out.println("Error");
    }
   }
}

4. Groovy HMAC SHA256

It is mostly Java code but there are some slight differences. Adapted from Dev Takeout - Groovy HMAC/SHA256 representation.

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.security.InvalidKeyException;

def hmac_sha256(String secretKey, String data) {
 try {
    Mac mac = Mac.getInstance("HmacSHA256")
    SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey.getBytes(), "HmacSHA256")
    mac.init(secretKeySpec)
    byte[] digest = mac.doFinal(data.getBytes())
    return digest
   } catch (InvalidKeyException e) {
    throw new RuntimeException("Invalid key exception while converting to HMac SHA256")
  }
}

def hash = hmac_sha256("secret", "Message")
encodedData = hash.encodeBase64().toString()
log.info(encodedData)

5. C# HMAC SHA256

using System.Security.Cryptography;

namespace Test
{
  public class MyHmac
  {
    private string CreateToken(string message, string secret)
    {
      secret = secret ?? "";
      var encoding = new System.Text.ASCIIEncoding();
      byte[] keyByte = encoding.GetBytes(secret);
      byte[] messageBytes = encoding.GetBytes(message);
      using (var hmacsha256 = new HMACSHA256(keyByte))
      {
        byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
        return Convert.ToBase64String(hashmessage);
      }
    }
  }
}

6. Go programming language - Golang HMAC SHA256

Try it online in your browser with Play GoLang
crypto/hmac package
package main

import (
    "crypto/hmac"
    "crypto/sha256"
    "encoding/base64"
    "fmt"
)

func ComputeHmac256(message string, secret string) string {
    key := []byte(secret)
    h := hmac.New(sha256.New, key)
    h.Write([]byte(message))
    return base64.StdEncoding.EncodeToString(h.Sum(nil))
}

func main() {
    fmt.Println(ComputeHmac256("Message", "secret"))
}

7. Ruby HMAC SHA256

Requires openssl and base64.

require 'openssl'
require "base64"

hash  = OpenSSL::HMAC.digest('sha256', "secret", "Message")
puts Base64.encode64(hash)

8. Python (2.7) HMAC SHA256

import hashlib
import hmac
import base64

message = bytes("Message").encode('utf-8')
secret = bytes("secret").encode('utf-8')

signature = base64.b64encode(hmac.new(secret, message, digestmod=hashlib.sha256).digest())
print(signature)
Tested with Python . Also, be sure not to name your python demo script the same as one of the imported libraries.

9. Perl HMAC SHA256

See Digest::SHA documentation. By convention, the Digest modules . We will use a modulus function below.

use Digest::SHA qw(hmac_sha256_base64);
$digest = hmac_sha256_base64("Message", "secret");

# digest is currently: qnR8UCqJggD55PohusaBNviGoOJ67HC6Btry4qXLVZc

# Fix padding of Base64 digests
) {
    $digest .= '=';
}

print $digest;
# digest is now: qnR8UCqJggD55PohusaBNviGoOJ67HC6Btry4qXLVZc=

10. Dart HMAC SHA256

Dependent upon the Dart crypto package.

import 'dart:html';
import 'dart:convert';
import 'package:crypto/crypto.dart';

void main() {

  String secret = 'secret';
  String message = 'Message';

  List<int> secretBytes = UTF8.encode('secret');
  List<int> messageBytes = UTF8.encode('Message');

  var hmac = new HMAC(new SHA256(), secretBytes);
  hmac.add(messageBytes);
  var digest = hmac.close();

  var hash = CryptoUtils.bytesToBase64(digest);

  // output to html page
  querySelector('#hash').text = hash;
  // hash => qnR8UCqJggD55PohusaBNviGoOJ67HC6Btry4qXLVZc=
}

11. Swift HMAC SHA256

I have not verified but see this stackOverflow post

Rust

Take a look at the alco/rust-digest repository for Rust (lang) guidance. I have not verified yet.

Powershell (Windows) HMAC SHA256

Mostly wrapping of .NET libraries but useful to see it in powershell's befuddling syntax. See code as gist

$message = 'Message'
$secret = 'secret'

$hmacsha = New-Object System.Security.Cryptography.HMACSHA256
$hmacsha.key = [Text.Encoding]::ASCII.GetBytes($secret)
$signature = $hmacsha.ComputeHash([Text.Encoding]::ASCII.GetBytes($message))
$signature = [Convert]::ToBase64String($signature)

echo $signature

# Do we get the expected signature?
echo ($signature -eq 'qnR8UCqJggD55PohusaBNviGoOJ67HC6Btry4qXLVZc=')