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();            FileOutputStream fs = new FileOutputStream("c:/abc.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();        }    }

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();    }