Java文件下载（excel）

最简单的方法就是把文件链接写到a标签的href里，但是有人说了，这样会暴露服务器的文件路径，有风险- -

下面整理介绍几种通过代码实现的方法：

1，

@RequestMapping("download")
public ResponseEntity<byte[]> download(HttpServletRequest request) throws Exception {
String fileName = request.getParameter("fileName");
String path = request.getSession().getServletContext().getRealPath("")+File.separator+"WEB-INF"+File.separator+"download";
File file = new File(path,fileName);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
headers.setContentDispositionFormData("attachment", fileName);
return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),headers, HttpStatus.CREATED);
}

spring里的方法，跟response无关。

2，

web.xml中

<servlet-mapping>
<servlet-name>DownloadServlet</servlet-name>
<url-pattern>/files/*</url-pattern>
</servlet-mapping>

public void fileOutputStream(HttpServletRequest req, HttpServletResponse resp){
String filepath = req.getRequestURI();
int index = filepath.indexOf(Global.USERFILES_BASE_URL);
if(index >= 0) {
filepath = filepath.substring(index + Global.USERFILES_BASE_URL.length());
}
try {
filepath = UriUtils.decode(filepath, "UTF-8");
} catch (UnsupportedEncodingException e1) {
logger.error(String.format("解释文件路径失败，URL地址为%s", filepath), e1);
}
File file = new File(Global.getUserfilesBaseDir() + Global.USERFILES_BASE_URL + filepath);
try {
FileCopyUtils.copy(new FileInputStream(file), resp.getOutputStream());
resp.setHeader("Content-Type", "application/octet-stream");
return;
} catch (FileNotFoundException e) {
req.setAttribute("exception", new FileNotFoundException("请求的文件不存在"));
req.getRequestDispatcher("/WEB-INF/views/error/404.jsp").forward(req, resp);
}
}

这个方法是通过servlet拦截url请求，如果匹配到相应的路径，则下载。

3，

@RequestMapping("/exportExcel")
public void exportExcel(HttpServletRequest request,HttpServletResponse response) {
try {
String filepath = ;//已存在的文件路径
FileInputStream fis = null;
OutputStream os = null;
try {
String downLoadName = new String("导出.xls".getBytes("gbk"), "iso8859-1");
fis = new FileInputStream(filepath);
os = response.getOutputStream();// 取得输出流
response.reset();// 清空输出流
response.setHeader("Content-disposition",
"attachment; filename=" + downLoadName);// 设定输出文件头
response.setContentType("application/x-download;charset=GBK;");
byte[] mybyte = new byte[fis.available()];
int len = 0;
while ((len = fis.read(mybyte)) != -1) {
os.write(mybyte, 0, len);
}
os.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
}

这个方法其实和法2类似，都是写到response中，只不过法2用FileCopyUtils.copy()简化了操作。

记住：下载之前得确定路径正确且路径下确实存在文件哦。