code: public static String file2String(File file) throws IOException {
          if (file == null || !file.exists() || !file.isFile() || !file.canRead()) {
              return null;
          }
          FileReader reader = null;
          StringWriter writer = null;
          try {
              reader = new FileReader(file);
              writer = new StringWriter();
              char[] cbuf = new char[1024];
              int len = 0;
              while ((len = reader.read(cbuf)) != -1) {
                  writer.write(cbuf, 0, len);
              }
              return writer.toString();
          } finally {
              IOUtils.closeQuietly(reader);
              IOUtils.closeQuietly(writer);
          }
      }
docs: 读取文件内容
  
  @param file 文件
  @return 文件内容
  @throws IOException 发送IO异常