Spring MVC实现文件下载-优快云博客

本文介绍了两种使用Spring MVC实现文件下载的方法。一种是通过返回ResponseEntity对象来完成文件的下载，另一种是直接通过Servlet API将文件内容写入到响应流中。文中还提供了具体的代码实现，并附上了相关资源链接。

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方法一：

    @RequestMapping("/testHttpMessageDown")
    public ResponseEntity<byte[]> download(HttpServletRequest request) throws IOException {
        File file = new File(request.getSession().getServletContext().getClassLoader().getResource("test.xlsx").getPath());
        byte[] body = null;
        InputStream is = new FileInputStream(file);
        body = new byte[is.available()];
        is.read(body);
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Disposition", "attchement;filename=" + file.getName());
        HttpStatus statusCode = HttpStatus.OK;
        ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(body, headers, statusCode);
        return entity;
    }

方法二：

    /*
     * Download a file from 
     *   - inside project, located in resources folder.
     *   - outside project, located in File system somewhere. 
     */
    @RequestMapping(value="/download", method = RequestMethod.GET)
    public void downloadFile(HttpServletRequest request, HttpServletResponse response) throws IOException {
    
        File file = new File(request.getSession().getServletContext().getClassLoader().getResource("test.xlsx").getPath());
        
        if(!file.exists()){
            String errorMessage = "Sorry. The file you are looking for does not exist";
            System.out.println(errorMessage);
            OutputStream outputStream = response.getOutputStream();
            outputStream.write(errorMessage.getBytes(Charset.forName("UTF-8")));
            outputStream.close();
            return;
        }
        
        String mimeType= URLConnection.guessContentTypeFromName(file.getName());
        if(mimeType==null){
            System.out.println("mimetype is not detectable, will take default");
            mimeType = "application/octet-stream";
        }
        
        System.out.println("mimetype : "+mimeType);
        
        response.setContentType(mimeType);
        
        /* "Content-Disposition : inline" will show viewable types [like images/text/pdf/anything viewable by browser] right on browser 
            while others(zip e.g) will be directly downloaded [may provide save as popup, based on your browser setting.]*/
        response.setHeader("Content-Disposition", String.format("inline; filename=\"" + file.getName() +"\""));

        
        /* "Content-Disposition : attachment" will be directly download, may provide save as popup, based on your browser setting*/
        //response.setHeader("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
        
        response.setContentLength((int)file.length());

        InputStream inputStream = new BufferedInputStream(new FileInputStream(file));

        //Copy bytes from source to destination(outputstream in this example), closes both streams.
        FileCopyUtils.copy(inputStream, response.getOutputStream());
    }