code: public static PemObject readPemObject(InputStream keyStream) {
  		PemReader pemReader = null;
  		try {
  			pemReader = new PemReader(IoUtil.getReader(keyStream, CharsetUtil.CHARSET_UTF_8));
  			return pemReader.readPemObject();
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		} finally {
  			IoUtil.close(pemReader);
  		}
  	}
docs: 读取pem文件中的信息，包括类型、头信息和密钥内容
  
  @param keyStream pem流
  @return {@link PemObject}
  @since 4.5.2