使用java原生API模拟请求下载文件

     /**
      *
      * @param urlPath
      *            下载路径
      * @param saveDir
      *            下载存放目录
      * @return 返回下载文件
      * @throws Exception
      */
     public static void downloadFile(String urlPath, String saveDir) throws Exception {
         URL url = new URL(urlPath);
         // 连接类的父类，抽象类
         URLConnection urlConnection = url.openConnection();
         // http的连接类
         HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
         // 设定请求的方法，默认是GET
         httpURLConnection.setRequestMethod("GET");
         // 设置字符编码
         httpURLConnection.setRequestProperty("Charset", "UTF-8");
         //状态码 200：成功连接
         int code = httpURLConnection.getResponseCode();
         if (code == 200) {
             System.out.println("链接地址成功！");
         }
         InputStream inputStream = httpURLConnection.getInputStream();
         File file = new File(saveDir);
         OutputStream out = new FileOutputStream(file);
         int size = 0;
         byte[] buf = new byte[1024];
         while ((size = inputStream.read(buf)) != -1) {
             out.write(buf, 0, size);
         }
         inputStream.close();
         out.close();
     }