字节流

    @PostMapping("/downloadExcel")
    public ResponseEntity<byte[]> downloadExcel() throws Exception {
        // Excel文件名
        String fileName = "StockInfo.xlsx";

        // 使用ByteArrayOutputStream作为输出流
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ExcelWriter excelWriter = EasyExcel.write(byteArrayOutputStream).build();
        WriteSheet writeSheet = EasyExcel.writerSheet("Data Sheet").build();

        // 准备要写入的数据
        List<List<Object>> data = new ArrayList<>();
        data.add(Arrays.asList("1","2","3","4","5","6"));

        // 将数据写入Excel
        excelWriter.write(data, writeSheet);
        // 关闭ExcelWriter
        excelWriter.finish();

        // 设置HTTP头部信息
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.parseMediaType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"));
        headers.setContentDispositionFormData("attachment", URLEncoder.encode(fileName, "UTF-8"));

        // 返回ResponseEntity，包含Excel文件内容和头部信息
        return ResponseEntity.ok().headers(headers).body(byteArrayOutputStream.toByteArray());
    }

文件流

    @PostMapping("/downloadExcel")
    public ResponseEntity<Resource> downloadExcel() throws Exception {
        // Excel文件名
        String fileName = "StockInfo.xlsx";
        // 创建Excel文件在服务器的临时存储路径
        File tempFile = File.createTempFile("StockInfo", ".xlsx");

        // 使用FileOutputStream作为输出流
        FileOutputStream fileOutputStream = new FileOutputStream(tempFile);
        ExcelWriter excelWriter = EasyExcel.write(fileOutputStream).build();
        WriteSheet writeSheet = EasyExcel.writerSheet("Data Sheet").build();

        // 准备要写入的数据
        List<List<Object>> data = new ArrayList<>();
        data.add(Arrays.asList("1","2","3","4","5","6"));

        // 将数据写入Excel
        excelWriter.write(data, writeSheet);
        // 关闭ExcelWriter
        excelWriter.finish();
        // 关闭文件输出流
        fileOutputStream.close();

        // 设置HTTP头部信息
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.parseMediaType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"));
        headers.setContentDispositionFormData("attachment", URLEncoder.encode(fileName, "UTF-8"));
        
        // 使用FileSystemResource包装文件，以便于在HTTP响应中传输
        Resource resource = new FileSystemResource(tempFile);

        // 返回ResponseEntity，包含Excel文件内容和头部信息
        return ResponseEntity.ok().headers(headers).contentLength(resource.contentLength()).body(resource);