Preface

In a project development , Using the Netty Network application framework , as well as MQTT Send and receive message data , This requires the background to actively push the obtained messages to the front end , So it was used MQTT, It is hereby recorded that .

One 、 What is? websocket？

WebSocket The protocol is based on TCP A new network protocol . It realizes full duplex communication between client and server , I've learned computer network , Since it's full duplex , It means that the server can actively send information to the client . This is in line with our push technology or the function of multi person online chat .

blockbuster ！Spring Boot 2.5.0 Hot release , Can you still learn to move ？

Why not use HTTP What about the agreement? ？ This is because HTTP It's simplex communication , Communication can only be initiated by the client , The client asks for , The server handles , This is too much trouble . therefore websocket emerge as the times require .

Dry goods ： In depth analysis of MySQL Index and SQL Tuning practice

Let's start using Springboot Start integrating . The following cases are all tested successfully on my own computer , You can modify it according to your own functions . My project structure is as follows ：

What is a data Lake ？ Why data lake ？ How to build a lake ？ how ETL？

Two 、 Use steps

1. Add dependency

Maven rely on ：

 <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
</dependency>

2. Enable Springboot Yes WebSocket Support for

Enable WebSocket The support is also very simple , A few lines of code ：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;
/**
* @ Auther: Ma Chaowei
* @ Date: 2020/06/16/14:35
* @ Description: Turn on WebSocket Support
*/
@Configuration
public class WebSocketConfig {
@Bean
public ServerEndpointExporter serverEndpointExporter() {
return new ServerEndpointExporter();
}
}

3. The core configuration ：WebSocketServer

because WebSocket It is similar to the form of client server ( use ws agreement ), So here WebSocketServer In fact, it's equivalent to a ws Agreed Controller

• @ ServerEndpoint An annotation is a class level annotation , Its main function is to define the current class as a websocket Server side , The value of the annotation will be used to monitor the terminal access of the user connection URL Address , The client can use this URL To connect to WebSocket Server side
• Create a new one ConcurrentHashMap webSocketMap Used to receive the current userId Of WebSocket, It's convenient to pass between userId Push messages .

Here is the specific business code ：

package cc.mrbird.febs.external.webScoket;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.time.LocalDateTime;
import java.util.List;
import java.util.concurrent.CopyOnWriteArraySet;
/**
* Created with IntelliJ IDEA.
* @ Auther: Ma Chaowei
* @ Date: 2020/06/16/14:35
* @ Description:
* @ ServerEndpoint An annotation is a class level annotation , Its main function is to define the current class as a websocket Server side ,
* The value of the annotation will be used to monitor the terminal access of the user connection URL Address , The client can use this URL To connect to WebSocket Server side
*/
@Component
@Slf4j
@Service
@ServerEndpoint("/api/websocket/{sid}")
public class WebSocketServer {
// Static variables , To record the current number of online connections . It should be designed to be thread safe .
private static int onlineCount = 0;
//concurrent Thread safety of package Set, Used to store the corresponding MyWebSocket object .
private static CopyOnWriteArraySet<WebSocketServer> webSocketSet = new CopyOnWriteArraySet<WebSocketServer>();
// A connection session with a client , It is needed to send data to the client
private Session session;
// receive sid
private String sid = "";
/**
* Connection establishment method called successfully
*/
@OnOpen
public void onOpen(Session session, @PathParam("sid") String sid) {
this.session = session;
webSocketSet.add(this); // Join in set in
this.sid = sid;
addOnlineCount(); // The online number 1
try {
sendMessage("conn_success");
log.info(" There's a new window to start listening :" + sid + ", The current online population is :" + getOnlineCount());
} catch (IOException e) {
log.error("websocket IO Exception");
}
}
/**
* Connection closes the called method
*/
@OnClose
public void onClose() {
webSocketSet.remove(this); // from set Delete in
subOnlineCount(); // The online number minus 1
// When disconnected , Update motherboard occupancy to release
log.info(" Released sid by ："+sid);
// Here you are When released , Business to deal with
log.info(" There is a connection closed ！ The current online population is " + getOnlineCount());
}
/**
* Method called upon receipt of a client message
* @ Param message The message sent by the client
*/
@OnMessage
public void onMessage(String message, Session session) {
log.info(" Received from window " + sid + " Information about :" + message);
// Group-sent message
for (WebSocketServer item : webSocketSet) {
try {
item.sendMessage(message);
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* @ Param session
* @ Param error
*/
@OnError
public void onError(Session session, Throwable error) {
log.error(" An error occurred ");
error.printStackTrace();
}
/**
* Realize server active push
*/
public void sendMessage(String message) throws IOException {
this.session.getBasicRemote().sendText(message);
}
/**
* Group custom messages
*/
public static void sendInfo(String message, @PathParam("sid") String sid) throws IOException {
log.info(" Push message to window " + sid + ", Push content :" + message);
for (WebSocketServer item : webSocketSet) {
try {
// You can only push this one here sid Of , by null Then all push
if (sid == null) {
// item.sendMessage(message);
} else if (item.sid.equals(sid)) {
item.sendMessage(message);
}
} catch (IOException e) {
continue;
}
}
}
public static synchronized int getOnlineCount() {
return onlineCount;
}
public static synchronized void addOnlineCount() {
WebSocketServer.onlineCount++;
}
public static synchronized void subOnlineCount() {
WebSocketServer.onlineCount--;
}
public static CopyOnWriteArraySet<WebSocketServer> getWebSocketSet() {
return webSocketSet;
}
}

4. test Controller

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
/**
* Created with IntelliJ IDEA.
*
* @ Auther: Ma Chaowei
* @ Date: 2020/06/16/14:38
* @ Description:
*/
@Controller("web_Scoket_system")
@RequestMapping("/api/socket")
public class SystemController {
// Page request
@GetMapping("/index/{userId}")
public ModelAndView socket(@PathVariable String userId) {
ModelAndView mav = new ModelAndView("/socket1");
mav.addObject("userId", userId);
return mav;
}
// Push data interface
@ResponseBody
@RequestMapping("/socket/push/{cid}")
public Map pushToWeb(@PathVariable String cid, String message) {
Map<String,Object> result = new HashMap<>();
try {
WebSocketServer.sendInfo(message, cid);
result.put("code", cid);
result.put("msg", message);
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
}

5. The test page index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Java Back end WebSocket Of Tomcat Realization </title>
<script type="text/javascript" src="js/jquery.min.js"></script>
</head>
<body>
<div id="main" style="width: 1200px;height:800px;"></div>
Welcome<br/><input id="text" type="text" />
<button onclick="send()"> Send a message </button>
<hr/>
<button onclick="closeWebSocket()"> close WebSocket Connect </button>
<hr/>
<div id="message"></div>
</body>
<script type="text/javascript">
var websocket = null;
// Determine whether the current browser supports it WebSocket
if('WebSocket' in window) {
// Change your address to
websocket = new WebSocket("ws://192.168.100.196:8082/api/websocket/100");
} else {
alert(' Current browser Not support websocket')
}
// Callback method for connection error
websocket.onerror = function() {
setMessageInnerHTML("WebSocket Connection error ");
};
// Callback method for successful connection establishment
websocket.onopen = function() {
setMessageInnerHTML("WebSocket Successful connection ");
}
var U01data, Uidata, Usdata
// The callback method that receives the message
websocket.onmessage = function(event) {
console.log(event);
setMessageInnerHTML(event);
setechart()
}
// Call-back method for connection closure
websocket.onclose = function() {
setMessageInnerHTML("WebSocket Connection is closed ");
}
// Listen for window closing events , When the window closes , Active close websocket Connect , Prevent Windows from closing before the connection has been disconnected ,server The end throws an exception .
window.onbeforeunload = function() {
closeWebSocket();
}
// Displays the message on the web page
function setMessageInnerHTML(innerHTML) {
document.getElementById('message').innerHTML += innerHTML + '<br/>';
}
// close WebSocket Connect
function closeWebSocket() {
websocket.close();
}
// Send a message
function send() {
var message = document.getElementById('text').value;
websocket.send('{"msg":"' + message + '"}');
setMessageInnerHTML(message + "&#13;");
}
</script>
</html>

6. Result display

backstage ： If there is a connection request

The front desk shows ：

Regular expressions are commonly used （ Quick reference manual ）

summary

I have a problem in the middle , That is to say WebSocket Start up prior to spring Containers , Which leads to WebSocketServer Call business in Service Null pointer exception will be reported

So you need to be in WebSocketServer Will be used in the service Give static initialization ： As shown in the figure ：

Spring Security 5.5 Release , Formal dress OAuth2.0 The fifth mode of Authorization

You also need to do the following configuration ：

520, Send a wave of high quality Java Classic books ！ There must be something you want that hasn't started yet ！