使用HttpURLConnection发送POST请求并携带请求参数

1、先创建URL对象，指定请求的URL地址。

URL url = new URL("http://example.com/api");

2、调用URL对象的openConnection()方法创建HttpURLConnection对象。

HttpURLConnection connection = (HttpURLConnection) url.openConnection();

3、设置请求方法为POST。

connection.setRequestMethod("POST");

4、设置请求头，包括Content-Type、Content-Length等。其中Content-Type表示请求体的格式，Content-Length表示请求体的长度。

connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");connection.setRequestProperty("Content-Length", String.valueOf(param.getBytes().length));

5、设置连接超时和读取超时时间。

connection.setConnectTimeout(5000);connection.setReadTimeout(5000);

6、允许向服务器写入写出数据。

connection.setDoOutput(true);connection.setDoInput(true);

7、获取输出流，向服务器写入数据。

OutputStream outputStream = connection.getOutputStream();outputStream.write(param.getBytes());outputStream.flush();outputStream.close();

这里的param是请求参数，需要将其转换为字节数组后写入输出流。

8、获取响应码，判断请求是否成功。

int statusCode = connection.getResponseCode();

9、读取响应数据。

InputStream inputStream = statusCode == 200 ? connection.getInputStream() : connection.getErrorStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));StringBuilder response = new StringBuilder();String line;while ((line = reader.readLine()) != null) {response.append(line);}reader.close();inputStream.close();

这里的response是响应数据，需要将其读取为字符串后使用。
完整的示例代码如下所示：

String param = "name=张三&age=18";URL url = new URL("http://example.com/api");HttpURLConnection connection = (HttpURLConnection) url.openConnection();connection.setRequestMethod("POST");connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");connection.setRequestProperty("Content-Length", String.valueOf(param.getBytes().length));connection.setConnectTimeout(5000);connection.setReadTimeout(5000);connection.setDoOutput(true);OutputStream outputStream = connection.getOutputStream();outputStream.write(param.getBytes());outputStream.flush();outputStream.close();int statusCode = connection.getResponseCode();InputStream inputStream = statusCode == 200 ? connection.getInputStream() : connection.getErrorStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));StringBuilder response = new StringBuilder();String line;while ((line = reader.readLine()) != null) { response.append(line);}reader.close();inputStream.close();connection.disconnect();System.out.println(response.toString());

需要注意的是，以上示例代码中的请求参数是以字符串形式传递的，如果需要传递复杂的请求参数，可以考虑使用JSON等格式。同时，如果请求的URL需要携带查询参数，可以在URL中添加查询参数。

下面使用HttpURLConnection 发送POST 请求 参数类型是json

下面是使用HttpURLConnection微信小程序发送订阅消息的一个例子

POST请求

json组装成了一个JSONObject

json类似是这样的

{"touser": "OPENID","template_id": "TEMPLATE_ID","page": "index","data": {"name01": {"value": "某某"},"amount01": {"value": "￥100"},"thing01": {"value": "广州至北京"} ,"date01": {"value": "2018-01-01"}}}

try {URL url = new URL(" https://api.weixin.qq.com/cgi-bin/message/subscribe/send?" +"access_token=" +"自己的小程序token");HttpURLConnection connection = (HttpURLConnection) url.openConnection();connection.setRequestMethod("POST");connection.setRequestProperty("Content-Type", "application/json");connection.setDoOutput(true);connection.setDoInput(true);//构造发送给用户的订阅消息内容Map messageContent = new HashMap();messageContent.put("character_string1", new HashMap() {{put("value", "a123456789");}});messageContent.put("amount2", new HashMap() {{put("value", "1元");}});messageContent.put("thing3", new HashMap() {{put("value", "西安大学长安学区");}});messageContent.put("time4", new HashMap() {{put("value", "2021年10月20日");}});messageContent.put("thing5", new HashMap() {{put("value", "这是备注");}});JSONObject messageContentJson = new JSONObject(messageContent);//构造订阅消息Map subscribeMessage = new HashMap();subscribeMessage.put("touser", " 。。。");//填写你的接收者openidsubscribeMessage.put("template_id", " 填写你的模板ID");//填写你的模板IDsubscribeMessage.put("data", messageContentJson);JSONObject subscribeMessageJson = new JSONObject(subscribeMessage);/*String s = subscribeMessageJson.toJSONString();System.out.println("JSONString:" + s);*/String s1 = subscribeMessageJson.toString();System.out.println("String:" + s1);byte[] bytes = s1.getBytes();DataOutputStream wr = new DataOutputStream(connection.getOutputStream());wr.write(bytes);wr.close();int statusCode = connection.getResponseCode();InputStream inputStream = statusCode == 200 ? connection.getInputStream() : connection.getErrorStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));StringBuilder response = new StringBuilder();String line;while ((line = reader.readLine()) != null) {response.append(line);}reader.close();inputStream.close();connection.disconnect();System.out.println(response.toString());connection.disconnect();} catch (Exception e) {e.printStackTrace();}