【Java基础】- HttpURLConnection详解

public void testDoGet(){
        String api="";
        HttpURLConnection connection = null;
        InputStream in=null;
        BufferedReader reader=null;
        try{
            //构造一个URL对象
            URL url = new URL(api);
            //获取URLConnection对象
            connection= (HttpURLConnection) url.openConnection();
            //getOutputStream会隐含的进行connect(即：如同调用上面的connect()方法，所以在开发中不调用connect()也可以)
            in = connection.getInputStream();
            //通过InputStreamReader将字节流转换成字符串，在通过BufferedReader将字符流转换成自带缓冲流
            reader = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8));
            StringBuilder sb = new StringBuilder();
            String line = null;
            //按行读取
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
            String response= sb.toString();
            System.out.println(response);
        }catch (Exception exception){
            exception.printStackTrace();
        }finally {
            if (connection != null) {
                connection.disconnect();
            }
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

public void testDoPost(){
        String apiUrl = "https://www.goyeer.com/api";
        String username  = "Goyeer";
        String password  = "123456";
        String tenantUrl = "";
        HttpURLConnection conn = null;
        OutputStream out = null;
        InputStream in = null;
        String idToken = null;
        try
        {
           // 构造一个URL对象
            URL url = new URL(apiUrl);
            // 获取URLConnection对象
            conn = (HttpURLConnection) url.openConnection();
            // 限制socket等待建立连接的时间，超时将会抛出java.net.SocketTimeoutException
            conn.setConnectTimeout(3000);
            // 限制输入流等待数据到达的时间，超时将会抛出java.net.SocketTimeoutException
            conn.setReadTimeout(3000);
            // 设定请求的方法为"POST"，默认是GET
            conn.setRequestMethod("POST");
            // 设置传送的内容类型是json格式
            conn.setRequestProperty("Content-Type", "application/json;charset=utf-8");
            // 接收的内容类型也是json格式
            conn.setRequestProperty("Accept", "application/json;charset=utf-8");
            // 设置是否从httpUrlConnection读入，默认情况下是true
            conn.setDoInput(true);
            // 由于URLConnection在默认的情况下不允许输出，所以在请求输出流之前必须调用setDoOutput(true)。为一个HTTP URL将doOutput设置为true时，请求方法将由GET变为POST
            conn.setDoOutput(true);
            // 是否使用缓存，Post方式不能使用缓存
            conn.setUseCaches(false);
            // 准备数据
            JSONObject json = new JSONObject();
            json.put("username", username);
            json.put("password", DigestUtils.md5Hex(password));
            json.put("tenantUrl", tenantUrl);
            // 返回一个OutputStream，可以用来写入数据传送给服务器
            out = conn.getOutputStream();
            // 将数据写入到输出流中
            out.write(json.toString().getBytes(StandardCharsets.UTF_8));
            // 刷新管道
            out.flush();
            // 建立连接
            conn.connect();
            // 判断数字响应码是否是200
            int responseCode = conn.getResponseCode();
            String result="";
            if (responseCode == 200) {
                // 获取输入流
                in = conn.getInputStream();
                // 获取返回的内容
                StringWriter sw = new StringWriter();
                InputStreamReader reader = new InputStreamReader(in, StandardCharsets.UTF_8);
                char[] buffer = new char[4096];
                for (int n = 0; -1 != (n = reader.read(buffer)); ) {
                    sw.write(buffer, 0, n);
                }
                result = sw.toString();
                System.out.println(result);
            }
        }catch (Exception exception){
            exception.printStackTrace();
        }finally {
            if (conn != null) {
                conn.disconnect();
            }
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
        }
    }