java下载文件的四种方式

 

try
        {
            // path是指欲下载的文件的路径。
            String path = "D:/file/aa.zip";
            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，输出文件
            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();
        }

 

// 下载本地文件
        String fileName = "aa.zip"; // 文件的默认保存名
        
        // 读到流中
        InputStream inStream = new FileInputStream("aa.zip");// 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();
        }

 

 

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/aa.gif");
        
        try
        {
            URLConnection conn = url.openConnection();
            InputStream inStream = conn.getInputStream();
            FileOutputStream fs = new FileOutputStream("F:/aa.gif");
            
            byte[] buffer = new byte[1204];
            int length;
            while ((byteread = inStream.read(buffer)) != -1)
            {
                bytesum += byteread;
                System.out.println(bytesum);
                fs.write(buffer, 0, byteread);
            }
        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }

 

//支持在线打开文件的一种方式
    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();
    }