Java下载文件的几种方式含本地文件下载

1.以流的方式下载.
public HttpServletResponse download(String path, HttpServletResponse response) {
try {
// path是指欲下载的文件的路径。
File file = new File(path);
// 取得文件名。
String filename = file.getName();
// 取得文件的后缀名。
String ext = filename.substring(filename.lastIndexOf(“.”) + 1).toUpperCase();

        // 以流的形式下载文件。
        InputStream fis = new BufferedInputStream(new FileInputStream(path));
        byte[] buffer = new byte[fis.available()];
        fis.read(buffer);
        fis.close();
        // 清空response
        response.reset();
        // 设置response的Header
        response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
        response.addHeader("Content-Length", "" + file.length());
        OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
        response.setContentType("application/octet-stream");
        toClient.write(buffer);
        toClient.flush();
        toClient.close();
    } catch (IOException ex) {
        ex.printStackTrace();
    }
    return response;
}

2.下载本地文件
public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
// 下载本地文件
String fileName = “Operator.doc”.toString(); // 文件的默认保存名
// 读到流中
InputStream inStream = new FileInputStream(“c:/Operator.doc”);// 文件的存放路径
// 设置输出的格式
response.reset();
response.setContentType(“bin”);
response.addHeader(“Content-Disposition”, “attachment; filename=\”” + fileName + “\””);
// 循环取出流中的数据
byte[] b = new byte[100];
int len;
try {
while ((len = inStream.read(b)) > 0)
response.getOutputStream().write(b, 0, len);
inStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
3.下载网络文件
public void downloadNet(HttpServletResponse response) throws MalformedURLException {
// 下载网络文件
int bytesum = 0;
int byteread = 0;

    URL url = new URL("windine.blogdriver.com/logo.gif");

    try {
        URLConnection conn = url.openConnection();
        InputStream inStream = conn.getInputStream();
        //设置超时时间
        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)");
        // 下载本地的文件
        FileOutputStream fs = new FileOutputStream("c:/abc.gif");
        /** web下载放开此注释
     // 设置response的Header
        response.addHeader("Content-Disposition", "attachment;filename=" + new             String(filename.getBytes()));
        response.setContentType("application/octet-stream");

**/
byte[] buffer = new byte[1204];
int length;
while ((byteread = inStream.read(buffer)) != -1) {
//bytesum += byteread;
//System.out.println(bytesum);
fs.write(buffer, 0, byteread);
// web下载放开此注释
//response.getOutputStream().write(buffer, 0, byteread);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
4.支持在线打开的方式
public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception {
File f = new File(filePath);
if (!f.exists()) {
response.sendError(404, “File not found!”);
return;
}
BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
byte[] buf = new byte[1024];
int len = 0;

    response.reset(); // 非常重要
    if (isOnLine) { // 在线打开方式
        URL u = new URL("file:///" + filePath);
        response.setContentType(u.openConnection().getContentType());
        response.setHeader("Content-Disposition", "inline; filename=" + f.getName());
        // 文件名应该编码成UTF-8
    } else { // 纯下载方式
        response.setContentType("application/x-msdownload");
        response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());
    }
    OutputStream out = response.getOutputStream();
    while ((len = br.read(buf)) > 0)
        out.write(buf, 0, len);
    br.close();
    out.close();
}

5.springMVC文件下载更方便
@RequestMapping(value=”/download”,method=RequestMethod.GET) //匹配的是href中的download请求
public ResponseEntity download(HttpServletRequest request,@RequestParam(“filename”) String filename,
Model model) throws IOException{

    String downloadFilePath="D:\\userUploadFile\\Files";//从我们的上传文件夹中去取

    File file = new File(downloadFilePath+File.separator+filename);//新建一个文件

    HttpHeaders headers = new HttpHeaders();//http头信息

    String downloadFileName = new String(filename.getBytes("UTF-8"),"iso-8859-1");//设置编码

    headers.setContentDispositionFormData("attachment", downloadFileName);

    headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);

    //MediaType:互联网媒介类型  contentType：具体请求中的媒体类型信息

    return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),headers,HttpStatus.CREATED);

}