code: private static PublicKey getPublicKey(String modulus, String exponent) {
  		try {
  			BigInteger b1 = new BigInteger(modulus);
  			BigInteger b2 = new BigInteger(exponent);
  			KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC");
  			RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
  			return keyFactory.generatePublic(keySpec);
  		} catch (Exception e) {
  			LogUtil.writeErrorLog("构造RSA公钥失败：" + e);
  			return null;
  		}
  	}
docs: 使用模和指数生成RSA公钥 注意：此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同
  
  @param modulus
  模
  @param exponent
  指数
  @return