Java后台Controller实现文件下载操作
ywh22122 人气:0代码
参数：
1.filePath:文件的绝对路径（d:\download\a.xlsx）
2.fileName(a.xlsx)
3.编码格式(GBK)
4.response、request不介绍了，从控制器传入的http对象
代码片.
//控制器
@RequestMapping(UrlConstants.BLACKLIST_TESTDOWNLOAD)
public void downLoad(String filePath, HttpServletResponse response, HttpServletRequest request) throws Exception {
boolean is = myDownLoad("D:\\a.xlsx","a.xlsx","GBK",response,request);
if(is)
System.out.println("成功");
else
System.out.println("失败");
}
//下载方法
public boolean myDownLoad(String filePath,String fileName, String encoding, HttpServletResponse response, HttpServletRequest request){
File f = new File(filePath);
if (!f.exists()) {
try {
response.sendError(404, "File not found!");
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
String type = fileName.substring(fileName.lastIndexOf(".") + 1);
//判断下载类型 xlsx 或 xls 现在只实现了xlsx、xls两个类型的文件下载
if (type.equalsIgnoreCase("xlsx") || type.equalsIgnoreCase("xls")){
response.setContentType("application/force-download;charset=UTF-8");
final String userAgent = request.getHeader("USER-AGENT");
try {
if (StringUtils.contains(userAgent, "MSIE") || StringUtils.contains(userAgent, "Edge")) {// IE浏览器
fileName = URLEncoder.encode(fileName, "UTF8");
} else if (StringUtils.contains(userAgent, "Mozilla")) {// google,火狐浏览器
fileName = new String(fileName.getBytes(), "ISO8859-1");
} else {
fileName = URLEncoder.encode(fileName, "UTF8");// 其他浏览器
}
response.setHeader("Content-disposition", "attachment; filename=" + fileName);
} catch (UnsupportedEncodingException e) {
logger.error(e.getMessage(), e);
return false;
}
InputStream in = null;
OutputStream out = null;
try {
//获取要下载的文件输入流
in = new FileInputStream(filePath);
int len = 0;
//创建数据缓冲区
byte[] buffer = new byte[1024];
//通过response对象获取outputStream流
out = response.getOutputStream();
//将FileInputStream流写入到buffer缓冲区
while((len = in.read(buffer)) > 0) {
//使用OutputStream将缓冲区的数据输出到浏览器
out.write(buffer,0,len);
}
//这一步走完，将文件传入OutputStream中后，页面就会弹出下载框
} catch (Exception e) {
logger.error(e.getMessage(), e);
return false;
} finally {
try {
if (out != null)
out.close();
if(in!=null)
in.close();
} catch (IOException e) {
logger.error(e.getMessage(), e);
}
}
return true;
}else {
logger.error("不支持的下载类型！");
return false;
}
}
实现效果
1.火狐浏览器效果
2.chrome效果，自动下载
补充知识：文件上传/下载的几种写法(java后端)
文件上传
1、框架已经帮你获取到文件对象File了
public boolean uploadFileToLocale(File uploadFile,String filePath) {
boolean ret_bl = false;
try {
InputStream in = new FileInputStream(uploadFile);
ret_bl=copyFile(in,filePath);
} catch (Exception e) {
e.printStackTrace();
}
return ret_bl;
}
public boolean copyFile(InputStream in,String filePath) {
boolean ret_bl = false;
FileOutputStream os=null;
try {
os = new FileOutputStream(filePath,false);
byte[] b = new byte[8 * 1024];
int length = 0;
while ((length = in.read(b)) > 0) {
os.write(b, 0, length);
}
os.close();
in.close();
ret_bl = true;
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
if(os!=null){
os.close();
}
if(in!=null){
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return ret_bl;
}
}
2、天了个撸，SB架构师根本就飘在天空没下来，根本就没想文件上传这一回事
public String uploadByHttp(HttpServletRequest request) throws Exception{
String filePath=null;
List<String> fileNames = new ArrayList<>();
//创建一个通用的多部分解析器
CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver(request.getSession().getServletContext());
//判断 request 是否有文件上传,即多部分请求
if(multipartResolver.isMultipart(request)){
//转换成多部分request
MultipartHttpServletRequest multiRequest =multipartResolver.resolveMultipart(request);
MultiValueMap<String,MultipartFile> multiFileMap = multiRequest.getMultiFileMap();
List<MultipartFile> fileSet = new LinkedList<>();
for(Entry<String, List<MultipartFile>> temp : multiFileMap.entrySet()){
fileSet = temp.getValue();
}
String rootPath=System.getProperty("user.dir");
for(MultipartFile temp : fileSet){
filePath=rootPath+"/tem/"+temp.getOriginalFilename();
File file = new File(filePath);
if(!file.exists()){
file.mkdirs();
}
fileNames.add(temp.getOriginalFilename());
temp.transferTo(file);
}
}
}
3、神啊，我正在撸框架，请问HttpServletRequest怎么获取！！！！
(1)在web.xml中配置一个监听
<listener>
<listener-class>
org.springframework.web.context.request.RequestContextListener
</listener-class>
</listener>
(2)HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();
文件下载（直接用链接下载的不算），这比较简单
1、本地文件下载（即文件保存在本地）
public void fileDownLoad(HttpServletRequest request,HttpServletResponse response,String fileName,String filePath) throws Exception {
response.setCharacterEncoding("UTF-8");
//设置ContentType字段值
response.setContentType("text/html;charset=utf-8");
//通知浏览器以下载的方式打开
response.addHeader("Content-type", "appllication/octet-stream");
response.addHeader("Content-Disposition", "attachment;filename="+fileName);
//通知文件流读取文件
InputStream in = request.getServletContext().getResourceAsStream(filePath);
//获取response对象的输出流
OutputStream out = response.getOutputStream();
byte[] buffer = new byte[1024];
int len;
//循环取出流中的数据
while((len = in.read(buffer)) != -1){
out.write(buffer,0,len);
}
}
2、远程文件下载（即网上资源下载，只知道文件URI）
public static void downLoadFromUrl(String urlStr,String fileName,HttpServletResponse response){
try {
urlStr=urlStr.replaceAll("\\\\", "/");
URL url = new URL(urlStr);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
//设置超时间为3秒
conn.setConnectTimeout(3*1000);
//防止屏蔽程序抓取而返回403错误
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
//得到输入流
InputStream inputStream = conn.getInputStream();
response.reset();
response.setContentType("application/octet-stream; charset=utf-8");
response.setHeader("Content-Disposition", "attachment; filename=" + new String(fileName.getBytes("GBK"),"ISO8859_1"));
//获取响应报文输出流对象
//获取response对象的输出流
OutputStream out = response.getOutputStream();
byte[] buffer = new byte[1024];
int len;
//循环取出流中的数据
while((len = in.read(buffer)) != -1){
out.write(buffer,0,len);
}
} catch (Exception e) {
e.printStackTrace();
}
}
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