POST / HTTP 1.1
Host: api.boacompra.com
Accept: application/vnd.boacompra.com.v2+json; charset=UTF-8
Authorization: 10: 52e7178dea75ae0e71e0f8c2379e0278beb7e9d091763ee0a64e6719d2df0fc2
Content-Type: application/json

public class Header {
  private String secretKey = "ABCDE0987";
  private String storeId = "10";
  private String contentMD5;
  private String httpVerb;

  public Header(String content, String url) throws NoSuchAlgorithmException, MalformedURLException, UnsupportedEncodingException {
    this.setContentMd5(content);
    this.setHttpVerb(new URL(url));
  }

  private void setHttpVerb(URL url) {
    this.httpVerb = url.getPath() + (url.getQuery() != null ? '?' + url.getQuery() : "");
  }

  private void setContentMd5(String content) throws NoSuchAlgorithmException, UnsupportedEncodingException {
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte messageDigest[] = md.digest(content.getBytes("UTF-8"));
    this.contentMD5 =  new BigInteger(1,messageDigest).toString(16);
  }

  private String generateAuthorization() throws NoSuchAlgorithmException, InvalidKeyException, UnsupportedEncodingException {
    final String data = this.httpVerb+this.contentMD5;
    Mac mac = Mac.getInstance("HmacSHA256");
    mac.init(new SecretKeySpec(this.secretKey.getBytes("UTF8"), "HmacSHA256"));

    return Hex.encodeHexString(mac.doFinal(data.getBytes("UTF-8")));
  }

  public HashMap<String,String> generateHeader() throws InvalidKeyException, NoSuchAlgorithmException, UnsupportedEncodingException {
    HashMap<String, String> headers = new HashMap<>();
    headers.put("Accept", "application/vnd.boacompra.com.v2+json; charset=UTF-8");
    headers.put("Content-Type", "application/json");
    headers.put("Authorization", this.storeId+':'+this.generateAuthorization());

    return headers;

  }

}

String content = "{\"transaction-id\":123456789,\"amount\":10.57,\"notify-url\":\"https://virtualstore.com/notifications\",\"test-mode\":0}";

Header header = new Header(content, "https://api.boacompra.com/refunds");
HashMap<String, String> headerMap = header.generateHeader();

System.out.println(Arrays.asList(headerMap));

<?php

class header
{
    private $secretKey = 'ABCDE0987';
    private $storeId = 10;

    public function __construct($content, $url)
    {
        $this->setContentMd5($content);
        $this->setHttpVerb($url);
    }

    private function setContentMd5($content)
    {
        $this->contentMd5 = md5($content);
    }

    private function setHttpVerb($url)
    {
        if (parse_url($url, PHP_URL_QUERY)) {
            $this->httpVerb = parse_url($url, PHP_URL_PATH).'?'.parse_url($url, PHP_URL_QUERY);
        } else {
            $this->httpVerb = parse_url($url, PHP_URL_PATH);
        }
    }

    private function generateAuthorization()
    {
        return hash_hmac(
            'sha256',
            $this->httpVerb . $this->contentMd5,
            $this->secretKey
        );
    }




    public function generateHeader()
    {
$headers = array(
            'Accept' => 'application/vnd.boacompra.com.v2+json; charset=UTF-8',
            'Content-Type' => 'application/json',
            'Authorization' => $this->storeId . ':' . $this->generateAuthorization()
        );
        return $headers;
    }
}

echo 'POST EXAMPLE <br />';
$content = '{"transaction-id":123456789,"amount":10.57,"notify-url":"https://virtualstore.com/notifications","test-mode":0}';

$headerPost = new header($content, 'https://api.boacompra.com/refunds');
print_r($headerPost->generateHeader());

require 'uri'
require 'openssl'
require 'digest/md5'

class Header

   SECRET_KEY = 'ABCDE0987'
   STORE_ID = 10

   attr_reader :contentMD5, :httpVerb

   def initialize(content, url)
    setContentMD5(content)
    setHttpVerb(url)
   end

   private
   def setContentMD5(content)
      @contentMD5 = Digest::MD5.hexdigest(content).to_s
   end

   private
   def getQueryString(url)
    uri = URI(url)
    url.to_s.empty? || uri.query.nil? ? '' : '?' + uri.query
   end

   private
   def setHttpVerb(url)
    uri = URI::parse(url)
    @httpVerb = getQueryString(url).to_s.empty? ? uri.path : uri.path + "?" + getQueryString(url)
   end

   private
   def generateAuthorization()
    OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha256'), SECRET_KEY, @httpVerb + @contentMD5)
   end

   public
   def generateHeader()
    headers = {
     "Accept"           => 'application/vnd.boacompra.com.v2+json; charset=UTF-8',
     "Content-Type"     => 'application/json',
     "Authorization"    => STORE_ID.to_s + ":" + generateAuthorization()
    }
    headers
   end
end

puts '<pre>POST EXAMPLE <br />'
content = '{"transaction-id":123456789,"amount":10.57,"notify-url":"https://virtualstore.com/notifications","test-mode":0}';
headerGet = Header.new(content, 'https://api.boacompra.com/refunds')
puts headerGet.generateHeader()

"""Python 2.7"""
from urlparse import urlparse
import hashlib
import hmac
import md5

class Header:

  __secretKey = '123'
  __storeId = 10

  def __init__(self, content, url):
    self.__setHttpVerb(url)
    self.__setContentMd5(content)

  def __setHttpVerb(self, url):
    urlParsed = urlparse(url)
    self.__httpVerb = urlParsed.path + urlParsed.query

  def __setContentMd5(self, content):
    self.__contentMd5 = md5.new(content).hexdigest()

  def __generateAuthorization(self):
    return hmac.new(
      self.__secretKey,
      self.__httpVerb + self.__contentMd5,
      hashlib.sha256
    ).hexdigest()

  def generateHeader(self):
    return {
      'Accept': 'application/vnd.boacompra.com.v2+json; charset=UTF-8',
      'Content-Type': 'application/json',
      'Authorization': str(self.__storeId) + ':' + self.__generateAuthorization()
    }

from Header import Header

content = '{"transaction-id":123456789,"amount":10.57,"notify-url":"https://virtualstore.com/notifications","test-mode":0}'
url = 'https://api.boacompra.com/refunds'

a = Header(content, url)
print a.generateHeader()


"""Python 3.x"""
from urllib.parse import urlparse
import hashlib
import hmac

class Header:

  __secretKey = '123'
  __storeId = 10

  def __init__(self, content, url):
    self.__setHttpVerb(url)
    self.__setContentMd5(content)

  def __setHttpVerb(self, url):
    urlParsed = urlparse(url)
    self.__httpVerb = urlParsed.path + urlParsed.query

  def __setContentMd5(self, content):
    self.__contentMd5 = hashlib.md5(content.encode()).hexdigest()

  def __generateAuthorization(self):
    authContent = self.__httpVerb + self.__contentMd5

    return hmac.new(
      self.__secretKey.encode(),
      authContent.encode(),
      hashlib.sha256
    ).hexdigest()

  def generateHeader(self):
    return {
      'Accept': 'application/vnd.boacompra.com.v2+json; charset=UTF-8',
      'Content-Type': 'application/json',
      'Authorization': str(self.__storeId) + ':' + self.__generateAuthorization()
    }

from Header import Header

content = '{"transaction-id":123456789,"amount":10.57,"notify-url":"https://virtualstore.com/notifications","test-mode":0}'
url = 'https://api.boacompra.com/refunds'

a = Header(content, url)
print(a.generateHeader())

{
    "transaction-id": 123456789,
    "amount": 10.57,
    "notify-url": "https://virtualstore.com/notifications",
    "test-mode": 0,
    "reference": "BC-380465"
}

HTTP/1.1 201 Created
Content-type: application/vnd.boacompra.com.v2+json; charset=UTF-8
Location: /transactions/123456

{
    "refund-id":12345
}

{
    "errors": [
        {
            "code": "20614",
            "description": "transaction_not_found "
        }
    ]
}

{
  "errors": [
    {
      "property": "transaction-id",
      "constraint": "required",
      "code": 20698,
      "description": "The property transaction-id is required"
    },
    {
      "property": "amount",
      "constraint": "minimum",
      "minimum": 0.01,
      "code": 20698,
      "description": "Must have a minimum value of 0.01"
    }
  ]
}

{
 "notification-type": "refund",
 "refund-id": 12345,
 "transaction-id": 75040384
}