SpringMVC文件下载

基于此篇文章中的一些没有注释的相关问题，今天进行SpringMVC的文件下载的更新：

新方法：

1.控制层，新建一个方法，返回值类型为ResponseEntity<byte[]>的方法，并在其函数的后面添加对应的后台需要处理的参数,比如可以传递FIleName

 /**
     * 文件下载
     *
     * @param id
     * @return
     */
    @GetMapping("/download/")
    public ResponseEntity<byte[]> download(@PathVariable("id") String id) throws IOException {
        File file = xxxService.buildXlsFileById(id);
        return ResponseUtils.buildResponseEntity(file);
    }

2. 编写service返回File文件对象,从Service层中查询数据库操作，并查询文件真正的路径位置，然后返回File对象

public File buildXlsById(String id){
       //do something to find this file
       File file=new File("1.txt");
       return file;
}  

　3. 编写ResponseUtils中的相关方法

/**
     * 构建下载类
     * @param file
     * @return
     * @throws IOException
     */
    public static ResponseEntity<byte[]> buildResponseEntity(File file) throws IOException {
        byte[] body = null;
        //获取文件
        InputStream is = new FileInputStream(file);
        body = new byte[is.available()];
        is.read(body);
        HttpHeaders headers = new HttpHeaders();
        //设置文件类型
        headers.add("Content-Disposition", "attchement;filename=" + file.getName());
        //设置Http状态码
　　　　 HttpStatus statusCode = HttpStatus.OK;
        //返回数据
　　　　 ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(body, headers, statusCode);
        return entity;
    }

　　

　　4.编写相对应得URL即可

老方法

/**
     * 文件下载
     * @Description: 
     * @param fileName
     * @param request
     * @param response
     * @return
     */
    @RequestMapping("/download")
    public String downloadFile(@RequestParam("fileName") String fileName,
            HttpServletRequest request, HttpServletResponse response) {
        if (fileName != null) {
            String realPath = request.getServletContext().getRealPath(
                    "WEB-INF/File/");
            File file = new File(realPath, fileName);
            if (file.exists()) {
                response.setContentType("application/force-download");// 设置强制下载不打开
                response.addHeader("Content-Disposition",
                        "attachment;fileName=" + fileName);// 设置文件名
                byte[] buffer = new byte[1024];
                FileInputStream fis = null;
                BufferedInputStream bis = null;
                try {
                    fis = new FileInputStream(file);
                    bis = new BufferedInputStream(fis);
                    OutputStream os = response.getOutputStream();
                    int i = bis.read(buffer);
                    while (i != -1) {
                        os.write(buffer, 0, i);
                        i = bis.read(buffer);
                    }
                } catch (Exception e) {
                    // TODO: handle exception
                    e.printStackTrace();
                } finally {
                    if (bis != null) {
                        try {
                            bis.close();
                        } catch (IOException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                    if (fis != null) {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
        return null;
    }