ahao-spring-boot-file-download

简介

作为后端开发, 最经常的需求就是导出Excel表的需求, 本质上就是下载文件的需求. 目前我了解到有4种下载方法

1. 临时文件下载(不依赖任何jar)
2. ServletOutputStream下载(依赖Servlet api)
3. 返回ResponseEntity下载(依赖Spring)
4. 返回View下载(依赖Spring)

临时文件下载

将数据导出到Excel保存到本地临时文件夹/opt/file后, 使用nginx对静态资源做反向代理. 这样访问http://192.168.0.2/1.txt就可以直接下载/opt/file/1.txt文件了, 注意改成nginx所在主机的IP地址.

location / {
    root /opt/file;
    try_files $uri $uri/ =404;
}

然后写一个Shell定时删除30天前的临时文件.

#!/bin/sh
location="/opt/file/"
find $location -mtime +30 -type f | xargs rm -f

原生 ServletOutputStream 输出流下载

依赖Servlet-api

@GetMapping(value = "/download.txt")
public void download(HttpServletResponse response) throws IOException {
    // 1. 初始化响应头
    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition", "attachment; filename="+"hello"+".txt");
    
    // 2. 生成响应体
    byte[] buf = "你好世界".getBytes(StandardCharsets.UTF_8);
    OutputStream os = response.getOutputStream();
    os.write(buf);
    os.flush();
}

Resource 下载

@GetMapping(value = "/download.txt")
public ResponseEntity<Resource> download() {
    // 1. 初始化响应头
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    headers.add("Content-Disposition", "attachment; filename="+"hello"+".txt");
    
    // 2. 生成响应体
    byte[] buf = "你好世界".getBytes(StandardCharsets.UTF_8);
    ByteArrayInputStream bais = new ByteArrayInputStream(buf);
    Resource body = new InputStreamResource(bais);

    // 3. 返回
    return new ResponseEntity<>(body, headers, HttpStatus.OK);
}

View 下载

@GetMapping("/download.xlsx")
public View xlsx() {
    return new AbstractXlsxView() {
        @Override
        protected void buildExcelDocument(Map<String, Object> model, Workbook workbook, HttpServletRequest request, HttpServletResponse response) throws Exception {
            // 1. 设置文件名和响应头
            response.setHeader("Content-Disposition", "attachment; filename=\""+"hello.xlsx"+"\"");

            // 2. 写入数据
            Sheet sheet = workbook.createSheet();
            Row header = sheet.createRow(0);
            header.createCell(col).setCellValue("你好世界");
        }
    };
}