code: protected String read(InputStream inputStream) throws IOException {
          BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, encoding));
          StringBuffer stringBuffer = new StringBuffer();
          String line = reader.readLine();
          while (line != null) {
              stringBuffer.append(line).append("\n");
              line = reader.readLine();
          }
          return stringBuffer.toString();
      }
docs: 读取文件
  
  @param inputStream
  @return
  @throws IOException