code: public static PrivateKey loadPrivateKeyFromKeyStore(KeyStore keyStore,String alias,String keyPass){
          try {			
          	return (PrivateKey) keyStore.getKey(alias, keyPass.toCharArray());
  		} catch (Exception e) {
  			throw new RuntimeException(e);
  		}
      }
docs: 从KeyStore获取私钥
  @param location
  @param alias
  @param keyStore
  @param storePass
  @param keyPass
  @return