code: public static PrivateKey getSignCertPrivateKey() {
  		try {
  			Enumeration<String> aliasenum = keyStore.aliases();
  			String keyAlias = null;
  			if (aliasenum.hasMoreElements()) {
  				keyAlias = aliasenum.nextElement();
  			}
  			PrivateKey privateKey = (PrivateKey) keyStore.getKey(keyAlias,
  					SDKConfig.getConfig().getSignCertPwd().toCharArray());
  			return privateKey;
  		} catch (KeyStoreException e) {
  			LogUtil.writeErrorLog("getSignCertPrivateKey Error", e);
  			return null;
  		} catch (UnrecoverableKeyException e) {
  			LogUtil.writeErrorLog("getSignCertPrivateKey Error", e);
  			return null;
  		} catch (NoSuchAlgorithmException e) {
  			LogUtil.writeErrorLog("getSignCertPrivateKey Error", e);
  			return null;
  		}
  	}
docs: 通过keyStore 获取私钥签名证书PrivateKey对象
  
  @return