BTERHmacPostBodyDigest.java

package org.knowm.xchange.bter.service;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;

import javax.crypto.Mac;

import org.knowm.xchange.service.BaseParamsDigest;

import si.mazi.rescu.RestInvocation;

/**
 * This may be used as the value of a @HeaderParam, @QueryParam or @PathParam to create a digest of the post body (composed of @FormParam's). Don't
 * use as the value of a @FormParam, it will probably cause an infinite loop.
 * <p/>
 * This may be used for REST APIs where some parameters' values must be digests of other parameters. An example is the MtGox API v1, where the
 * Rest-Sign header parameter must be a digest of the request body (which is composed of @FormParams).
 */
public class BTERHmacPostBodyDigest extends BaseParamsDigest {

  /**
   * Constructor
   * 
   * @param secretKeyBase64
   * @throws IllegalArgumentException if key is invalid (cannot be base-64-decoded or the decoded key is invalid).
   */
  private BTERHmacPostBodyDigest(String secretKeyBase64) {

    super(secretKeyBase64, HMAC_SHA_512);
  }

  public static BTERHmacPostBodyDigest createInstance(String secretKeyBase64) {

    return secretKeyBase64 == null ? null : new BTERHmacPostBodyDigest(secretKeyBase64);
  }

  @Override
  public String digestParams(RestInvocation restInvocation) {

    try {
      String postBody = restInvocation.getRequestBody();
      Mac mac = getMac();
      mac.update(postBody.getBytes("UTF-8"));
      return String.format("%0128x", new BigInteger(1, mac.doFinal()));
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("Illegal encoding, check the code.", e);
    }
    // return Base64.encodeBytes(mac.doFinal()).trim();
  }
}