GET方法

@Test
    public void testGet() throws Exception {
        //1.确定要访问/爬取的URL
        URL url = new URL("https://www.itcast.cn/");

        //2.获取连接对象
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();

        //3.设置连接信息：请求方式/请求参数/请求头....
        urlConnection.setRequestMethod("GET");
        urlConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36");
        urlConnection.setConnectTimeout(30000);

        //4.获取数据
        InputStream in = urlConnection.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String line;
        String html = "";
        while ((line = reader.readLine()) != null){
            html += line + "\n";
        }
        System.out.println(html);

        //5.关闭资源
        in.close();
        reader.close();
    }

POST方法

@Test
    public void testPost() throws Exception {
        //1.确定URL
        URL url = new URL("https://www.itcast.cn/");
        //2.获取连接
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        //3.设置连接信息
        urlConnection.setDoOutput(true);
        urlConnection.setRequestMethod("POST"); //请求方式默认是GET
        urlConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36");
        urlConnection.setConnectTimeout(30000);
        OutputStream out = urlConnection.getOutputStream();
        out.write("username=xx".getBytes());

        //4.获取数据
        InputStream in = urlConnection.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String line;
        String html = "";
        while ((line = reader.readLine()) != null){
            html += line + "\n";
        }
        System.out.println(html);

        //5.关闭资源
        in.close();
        reader.close();
    }