Signing a Query Request

import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLEncoder;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SignatureException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;

public class SignatureExample {
    private static final String CHARACTER_ENCODING = "UTF-8";
    final static String ALGORITHM = "HmacSHA256";

    public static void main(String[] args) throws Exception {
        // Change this secret key to yours
        String secretKey = "Your secret key";

        // Use the endpoint for your marketplace
        String serviceUrl = "https://mws.amazonservices.com/";

        // Create set of parameters needed and store in a map
        HashMap<String, String> parameters = new HashMap<String,String>();

        // Add required parameters. Change these as needed.
        parameters.put("AWSAccessKeyId", urlEncode("Your Access Key Id"));
        parameters.put("Action", urlEncode("GetFeedSubmissionList"));
        parameters.put("MWSAuthToken", urlEncode("Your MWS Auth Token"));
        parameters.put("SellerId", urlEncode("Your Seller Id"));
        parameters.put("SignatureMethod", urlEncode(ALGORITHM));
        parameters.put("SignatureVersion", urlEncode("2"));
        parameters.put("SubmittedFromDate",
          urlEncode("2013-05-01T12:00:00Z"));
        parameters.put("Timestamp", urlEncode("2013-05-02T16:00:00Z"));
        parameters.put("Version", urlEncode("2009-01-01"));

        // Format the parameters as they will appear in final format
        // (without the signature parameter)
        String formattedParameters = calculateStringToSignV2(parameters,
            serviceUrl);

        String signature = sign(formattedParameters, secretKey);

        // Add signature to the parameters and display final results
        parameters.put("Signature", urlEncode(signature));
        System.out.println(calculateStringToSignV2(parameters,
            serviceUrl));
    }

    /* If Signature Version is 2, string to sign is based on following:
    *
    *    1. The HTTP Request Method followed by an ASCII newline (%0A)
    *
    *    2. The HTTP Host header in the form of lowercase host,
    *       followed by an ASCII newline.
    *
    *    3. The URL encoded HTTP absolute path component of the URI
    *       (up to but not including the query string parameters);
    *       if this is empty use a forward '/'. This parameter is followed
    *       by an ASCII newline.
    *
    *    4. The concatenation of all query string components (names and
    *       values) as UTF-8 characters which are URL encoded as per RFC
    *       3986 (hex characters MUST be uppercase), sorted using
    *       lexicographic byte ordering. Parameter names are separated from
    *       their values by the '=' character (ASCII character 61), even if
    *       the value is empty. Pairs of parameter and values are separated
    *       by the '&' character (ASCII code 38).
    *
    */
    private static String calculateStringToSignV2(
        Map<String, String> parameters, String serviceUrl)
            throws SignatureException, URISyntaxException {
        // Sort the parameters alphabetically by storing
        // in TreeMap structure
        Map<String, String> sorted = new TreeMap<String, String>();
        sorted.putAll(parameters);

        // Set endpoint value
        URI endpoint = new URI(serviceUrl.toLowerCase());

        // Create flattened (String) representation
        StringBuilder data = new StringBuilder();
        data.append("POST\n");
        data.append(endpoint.getHost());
        data.append("\n/");
        data.append("\n");

        Iterator<Entry<String, String>> pairs =
          sorted.entrySet().iterator();
        while (pairs.hasNext()) {
            Map.Entry<String, String> pair = pairs.next();
            if (pair.getValue() != null) {
                data.append( pair.getKey() + "=" + pair.getValue());
            }
            else {
                data.append( pair.getKey() + "=");
            }

            // Delimit parameters with ampersand (&)
            if (pairs.hasNext()) {
                data.append( "&");
            }
        }

        return data.toString();
    }

    /*
     * Sign the text with the given secret key and convert to base64
     */
    private static String sign(String data, String secretKey)
            throws NoSuchAlgorithmException, InvalidKeyException,
                   IllegalStateException, UnsupportedEncodingException {
        Mac mac = Mac.getInstance(ALGORITHM);
        mac.init(new SecretKeySpec(secretKey.getBytes(CHARACTER_ENCODING),
            ALGORITHM));
        byte[] signature = mac.doFinal(data.getBytes(CHARACTER_ENCODING));
        String signatureBase64 = new String(Base64.encodeBase64(signature),
            CHARACTER_ENCODING);
        return new String(signatureBase64);
    }

    private static String urlEncode(String rawValue) {
        String value = (rawValue == null) ? "" : rawValue;
        String encoded = null;

        try {
            encoded = URLEncoder.encode(value, CHARACTER_ENCODING)
                .replace("+", "%20")
                .replace("*", "%2A")
                .replace("%7E","~");
        } catch (UnsupportedEncodingException e) {
            System.err.println("Unknown encoding: " + CHARACTER_ENCODING);
            e.printStackTrace();
        }

        return encoded;
    }
  }

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