后端发送HTTP POST请求的代码：
protected void handleRequest(HttpServletRequest req, HttpServletResponse resp) throws IOException {
System.out.println("com.tievd.servlet.DevArceQueryServlet.handleRequest()");
JSONObject params = new JSONObject();
params.put("status", "ON");
params.put("appid", "黄毅123");
params.put("appsecret", "通过1110");
params.put("page_size", 3);
params.put("page_index", 1);
params.put("trade_id", "好123");
//创建执行请求的HttpClient对象
HttpClient client = HttpClients.createDefault();
String url = "http://localhost:8080/OutDataApi/QuerysDeviceChannels";
//创建post请求对象
HttpPost post = new HttpPost(url);
//创建StringEntity对象，并将参数封装到该对象中，注意必须设置编码格式，否则参数会乱码
StringEntity entity = new StringEntity(params.toString(), "UTF-8");
//将参数放入请求对象中
post.setEntity(entity);
//发送请求
HttpResponse response = client.execute(post);
if (response.getStatusLine().getStatusCode() == 200) {
//获取返回的数据
HttpEntity result = response.getEntity();
String messageString = EntityUtils.toString(result, "UTF-8");
System.out.println(messageString);
JSONObject message = JSONObject.fromObject(messageString);
}
}