code: public static PublicKey loadPublicKey(String publicKeyStr) throws Exception {
  		try {
  			byte[] buffer = base64.decode(publicKeyStr);
  			KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
  			X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
  			return (RSAPublicKey) keyFactory.generatePublic(keySpec);
  		} catch (NoSuchAlgorithmException e) {
  			throw new Exception("无此算法");
  		} catch (InvalidKeySpecException e) {
  			throw new Exception("公钥非法");
  		} catch (NullPointerException e) {
  			throw new Exception("公钥数据为空");
  		}
  	}
docs: 从字符串中加载公钥
  
  @param publicKeyStr
  公钥数据字符串
  @throws Exception
  加载公钥时产生的异常