Example in Java

import java.util.*;
import java.text.*;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.net.URLEncoder;
import java.net.URLDecoder;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

class MeridixSignature
{
	public static void main(String[] args) throws UnsupportedEncodingException, NoSuchAlgorithmException {
		String token = "gf94bfdds9bd4b8885466baa8dsc28";
		System.out.printf("Token:\n%s\n", token);
		
		String secret = "56fhu73df434a8";
		System.out.printf("Secret:\n%s\n", secret);
		
		String request = "http://site.meridix.se/api/customer/listcustomers";
		System.out.printf("Request:\n%s\n", request);
		
		String nonce = UUID.randomUUID().toString().substring(0, 8);
		System.out.printf("Nonce:\n%s\n", nonce);
		
		SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
		dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
		String timestamp = dateFormat.format(new Date());
		System.out.printf("Timestamp:\n%s\n", timestamp);
		
		List<String> parameters = new ArrayList<String>();
		parameters.add("auth_nonce=" + nonce);
		parameters.add("auth_timestamp=" + timestamp);
		parameters.add("auth_token=" + token);
		Collections.sort(parameters);
		
		String parametersConcated = org.apache.commons.lang3.StringUtils.join(parameters, "&");
		System.out.printf("ParametersConcated:\n%s\n", parametersConcated);
		
		String parametersConcatedEncoded = URLEncoder.encode(parametersConcated, "UTF-8");
		System.out.printf("ParametersConcatedEncoded:\n%s\n", parametersConcatedEncoded);
		
		String requestEncoded = URLEncoder.encode(request, "UTF-8");
		System.out.printf("RequestEncoded:\n%s\n", requestEncoded);
		
		// IMPORTANT - The GET&-prefix must be change to POST& etc. when using different HTTP Verbs than GET.
		String verbRequestQuery = "GET&" + requestEncoded + "&" + parametersConcatedEncoded + "&" + secret;
		System.out.printf("VerbRequestQuery:\n%s\n", verbRequestQuery);
		
		String signature = generateMD5Hash(verbRequestQuery);
		System.out.printf("Signature:\n%s\n", signature);
        String signedRequest = request + "?" + parametersConcated + "&auth_signature=" + signature;
		System.out.printf("SignedRequest:\n%s\n", signedRequest);
	}
	
	public static String pad(String s, int length, char pad) {
		StringBuffer buffer = new StringBuffer(s);
		while (buffer.length() < length) {
			buffer.insert(0, pad);
		}
		return buffer.toString();
	}
	
	public static String generateMD5Hash(String input) throws NoSuchAlgorithmException, UnsupportedEncodingException {
		MessageDigest digester = MessageDigest.getInstance("MD5");
		digester.update(input.getBytes("UTF-8"));
		return pad((new BigInteger(1,digester.digest())).toString(16),32,'0');
	}
}