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();
    }