code: public static boolean checkByPublicKey(String data, String sign, String publicKey) throws Exception {
  		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
  		byte[] encodedKey = base64.decode(publicKey);
  		PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));
  		java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
  		signature.initVerify(pubKey);
  		signature.update(data.getBytes("utf-8"));
  		return signature.verify(base64.decode(sign.getBytes("UTf-8")));
  	}
docs: 公钥验证签名
  @param data
  @param sign
  @param publicKey
  @return
  @throws Exception