java.net.URL请求远程文件下载

1:浏览器请求下载

    public void listStockcodeUplaod(HttpServletRequest req,
            HttpServletResponse res) throws Exception {
        String urlPath = req.getParameter("url");
        String name = req.getParameter("name");

        URL url = new URL(urlPath);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        // 设置超时间为3秒
        conn.setConnectTimeout(10 * 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();
        // 获取自己数组
        byte[] getData = new byte[1024];
        int len = 0;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while ((len = inputStream.read(getData)) != -1) {
            bos.write(getData, 0, len);
        }
        bos.close();
        getData = bos.toByteArray();

        // 以流的形式下载文件。
        // byte[] buffer = new byte[fis.available()];
        inputStream.read(getData);
        inputStream.close();
        // 清空response
        res.reset();
        // 设置response的Header
        res.addHeader("Content-Disposition", "attachment;filename=sss.pdf");
        res.addHeader("Content-Length", "" + getData.length);
        OutputStream toClient = new BufferedOutputStream(res.getOutputStream());
        res.setContentType("application/octet-stream");
        toClient.write(getData);
        toClient.flush();
        toClient.close();

        System.out.println("info:" + url + " download success");
    }

2.同上

    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;
    }

    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();
        }
    }

    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();
        }
    }

3.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();
    }

4 url下载到本地

/** 
     * 从网络Url中下载文件 
     * @param urlStr 
     * @param fileName 
     * @param savePath 
     * @throws IOException 
     */  
    public static void  downLoadFromUrl(String urlStr,String fileName,String savePath) throws IOException{  
        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();    
        //获取自己数组  
        byte[] getData = readInputStream(inputStream);      
  
        //文件保存位置  
        File saveDir = new File(savePath);  
        if(!saveDir.exists()){  
            saveDir.mkdir();  
        }  
        File file = new File(saveDir+File.separator+fileName);      
        FileOutputStream fos = new FileOutputStream(file);       
        fos.write(getData);   
        if(fos!=null){  
            fos.close();    
        }  
        if(inputStream!=null){  
            inputStream.close();  
        }  
  
  
        System.out.println("info:"+url+" download success");   
  
    }  
  
  
  
    /** 
     * 从输入流中获取字节数组 
     * @param inputStream 
     * @return 
     * @throws IOException 
     */  
    public static  byte[] readInputStream(InputStream inputStream) throws IOException {    
        byte[] buffer = new byte[1024];    
        int len = 0;    
        ByteArrayOutputStream bos = new ByteArrayOutputStream();    
        while((len = inputStream.read(buffer)) != -1) {    
            bos.write(buffer, 0, len);    
        }    
        bos.close();    
        return bos.toByteArray();    
    }    
  
    public static void main(String[] args) {  
        try{  
            downLoadFromUrl("http://101.95.48.97:8005/res/upload/interface/apptutorials/manualstypeico/6f83ce8f-0da5-49b3-bac8-fd5fc67d2725.png",  
                    "百度.jpg","d:/resource/images/diaodiao/country/");  
        }catch (Exception e) {  
            // TODO: handle exception  
        }  
    }