通过指定的 url 去网络或者文件服务器下载文件到本地某个文件夹

/**
     * 从网络Url中下载文件
     * @param urlStr   指定的url
     * @param fileName    下载文件到本地的名字
     * @param savePath     本地保存下载文件的路径
     * @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();
    }

　　//main函数测试
　　public static void main(String[] args) throws IOException {
        
        downLoadFromUrl("http://baidu.pdf","lq.pdf","d:/file/");
        //System.out.println(111);
        
    }