基于HmacSHA256的安全令牌

				Mac sha256_HMAC = null;
				BASE64Decoder decoder = null;
				BASE64Encoder encoder = null;
				try {
					decoder = new sun.misc.BASE64Decoder();
					SecretKey secret_key = new SecretKeySpec(decoder.decodeBuffer(sAccessKey), "HmacSHA256");
					sha256_HMAC = Mac.getInstance(secret_key.getAlgorithm());
					sha256_HMAC.init(secret_key);
					byte[] digest = sha256_HMAC.doFinal(sStringToSign.getBytes("UTF-8"));
					encoder = new sun.misc.BASE64Encoder();
					sToken = encoder.encode(digest); 
				} catch (NoSuchAlgorithmException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (InvalidKeyException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalStateException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (UnsupportedEncodingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}