某个文件放在springboot 的resources/file 位置下
读取方式：
1、方式一
ClassPathResource classPathResource =newClassPathResource("file/test.xlsx");
InputStream inputStream =classPathResource.getInputStream();
2、方式二
InputStream inputStream =Thread.currentThread().getContextClassLoader().getResourceAsStream("file/test.xlsx");
3、方式三
InputStream inputStream =this.getClass().getResourceAsStream("/file/test.xlsx");
4、方式四
File file = ResourceUtils.getFile("classpath:file/test.xlsx");
InputStream inputStream =new FileInputStream(file);
