Создайте простое приложение Chat с Spring Boot и Websocket

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
    http://maven.apache.org/xsd/maven-4.0.0.xsd">


    <modelVersion>4.0.0</modelVersion>

    <groupId>org.o7planning</groupId>
    <artifactId>SpringBootWebSocket</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>SpringBootWebSocket</name>
    <description>Spring Boot + WebSocket Example</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.2.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

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

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

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

package org.o7planning.springbootwebsocket;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootWebSocketApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootWebSocketApplication.class, args);
    }
    
}

var socket = new SockJS('/ws');
stompClient = Stomp.over(socket);

stompClient.connect({}, onConnected, onError);

// See more in main.js file.

package org.o7planning.springbootwebsocket.config;

import org.o7planning.springbootwebsocket.interceptor.HttpHandshakeInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
    
    @Autowired
    private HttpHandshakeInterceptor handshakeInterceptor;

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS().setInterceptors(handshakeInterceptor);
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.setApplicationDestinationPrefixes("/app");
        registry.enableSimpleBroker("/topic");
    }

}

package org.o7planning.springbootwebsocket.interceptor;

import java.util.Map;

import javax.servlet.http.HttpSession;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.HandshakeInterceptor;

@Component
public class HttpHandshakeInterceptor implements HandshakeInterceptor {

    private static final Logger logger = LoggerFactory.getLogger(HttpHandshakeInterceptor.class);
    
    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler,
            Map<String, Object> attributes) throws Exception {
        
        logger.info("Call beforeHandshake");
        
        if (request instanceof ServletServerHttpRequest) {
            ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) request;
            HttpSession session = servletRequest.getServletRequest().getSession();
            attributes.put("sessionId", session.getId());
        }
        return true;
    }

    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler,
            Exception ex) {
        logger.info("Call afterHandshake");
    }
    
}

package org.o7planning.springbootwebsocket.model;

public class ChatMessage {
    
    private MessageType type;
    private String content;
    private String sender;

    public enum MessageType {
        CHAT, JOIN, LEAVE
    }

    public MessageType getType() {
        return type;
    }

    public void setType(MessageType type) {
        this.type = type;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getSender() {
        return sender;
    }

    public void setSender(String sender) {
        this.sender = sender;
    }
    
}

package org.o7planning.springbootwebsocket.listener;

import org.o7planning.springbootwebsocket.model.ChatMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.event.EventListener;
import org.springframework.messaging.simp.SimpMessageSendingOperations;
import org.springframework.messaging.simp.stomp.StompHeaderAccessor;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.messaging.SessionConnectedEvent;
import org.springframework.web.socket.messaging.SessionDisconnectEvent;

@Component
public class WebSocketEventListener {

    private static final Logger logger = LoggerFactory.getLogger(WebSocketEventListener.class);

    @Autowired
    private SimpMessageSendingOperations messagingTemplate;

    @EventListener
    public void handleWebSocketConnectListener(SessionConnectedEvent event) {
        logger.info("Received a new web socket connection");
    }

    @EventListener
    public void handleWebSocketDisconnectListener(SessionDisconnectEvent event) {
        StompHeaderAccessor headerAccessor = StompHeaderAccessor.wrap(event.getMessage());

        String username = (String) headerAccessor.getSessionAttributes().get("username");
        
        if(username != null) {
            logger.info("User Disconnected : " + username);

            ChatMessage chatMessage = new ChatMessage();
            chatMessage.setType(ChatMessage.MessageType.LEAVE);
            chatMessage.setSender(username);

            messagingTemplate.convertAndSend("/topic/publicChatRoom", chatMessage);
        }
    }
    
}

package org.o7planning.springbootwebsocket.controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class MainController {

    @RequestMapping("/")
    public String index(HttpServletRequest request, Model model) {
        String username = (String) request.getSession().getAttribute("username");

        if (username == null || username.isEmpty()) {
            return "redirect:/login";
        }
        model.addAttribute("username", username);

        return "chat";
    }

    @RequestMapping(path = "/login", method = RequestMethod.GET)
    public String showLoginPage() {
        return "login";
    }

    @RequestMapping(path = "/login", method = RequestMethod.POST)
    public String doLogin(HttpServletRequest request, @RequestParam(defaultValue = "") String username) {
        username = username.trim();

        if (username.isEmpty()) {
            return "login";
        }
        request.getSession().setAttribute("username", username);

        return "redirect:/";
    }

    @RequestMapping(path = "/logout")
    public String logout(HttpServletRequest request) {
        request.getSession(true).invalidate();
        
        return "redirect:/login";
    }
    
}

package org.o7planning.springbootwebsocket.controller;

import org.o7planning.springbootwebsocket.model.ChatMessage;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
import org.springframework.stereotype.Controller;

@Controller
public class WebSocketController {



    @MessageMapping("/chat.sendMessage")
    @SendTo("/topic/publicChatRoom")
    public ChatMessage sendMessage(@Payload ChatMessage chatMessage) {
        return chatMessage;
    }

    @MessageMapping("/chat.addUser")
    @SendTo("/topic/publicChatRoom")
    public ChatMessage addUser(@Payload ChatMessage chatMessage, SimpMessageHeaderAccessor headerAccessor) {
        // Add username in web socket session
        headerAccessor.getSessionAttributes().put("username", chatMessage.getSender());
        return chatMessage;
    }

}

<!DOCTYPE html>
<html>
   <head>
      <title>Login</title>
      <link rel="stylesheet" href="/css/main.css" />
   </head>
   <body>
      <div id="login-container">
         <h1 class="title">Enter your username</h1>
         <form id="loginForm" name="loginForm" method="POST">
            <input type="text" name="username" />
            <button type="submit">Login</button>
         </form>
      </div>
   </body>
</html>

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <title>Spring Boot WebSocket</title>
      <link rel="stylesheet" th:href="@{/css/main.css}" />
      
      <!-- https://cdnjs.com/libraries/sockjs-client -->
      <script src="https://cdnjs.cloudflare.com/ajax/libs/sockjs-client/1.1.4/sockjs.min.js"></script>
      <!-- https://cdnjs.com/libraries/stomp.js/ -->
      <script  src="https://cdnjs.cloudflare.com/ajax/libs/stomp.js/2.3.3/stomp.min.js"></script>
      
   </head>
   <body>
      <div id="chat-container">
         <div class="chat-header">
            <div class="user-container">
               <span id="username" th:utext="${username}"></span>
               <a th:href="@{/logout}">Logout</a>
            </div>
            <h3>Spring WebSocket Chat Demo</h3>
         </div>
         
         <hr/>
         
         <div id="connecting">Connecting...</div>
         <ul id="messageArea">
         </ul>
         <form id="messageForm" name="messageForm">
            <div class="input-message">
               <input type="text" id="message" autocomplete="off"
                  placeholder="Type a message..."/>
               <button type="submit">Send</button>
            </div>
         </form>
      </div>
      
      <script th:src="@{/js/main.js}"></script>
      
   </body>
</html>

* {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

html, body {
    height: 100%;
    overflow: hidden;
}
 
#login-page {
    text-align: center;
}

.nickname  {
    color:blue;margin-right:20px;
}
.hidden {
    display: none;
}

.user-container {
    float: right;
    margin-right:5px;
}

#login-container {
    background: #f4f6f6 ;
    border: 2px solid #ccc;
    width: 100%;
    max-width: 500px;
    display: inline-block;
    margin-top: 42px;
    vertical-align: middle;
    position: relative;
    padding: 35px 55px 35px;
    min-height: 250px;
    position: absolute;
    top: 50%;
    left: 0;
    right: 0;
    margin: 0 auto;
    margin-top: -160px;
}
 

#chat-container {
    position: relative;
    height: 100%;
}

#chat-container #messageForm {
    padding: 20px;
}

#chat-container {
    border: 2px solid #d5dbdb;
    background-color:  #d5dbdb ;
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
    
    margin-top: 30px;
    height: calc(100% - 60px);
    max-height: 600px;
    position: relative;
    
}

#chat-container ul {
    list-style-type: none;
    background-color: #fff;
    margin: 0;
    overflow: auto;
    overflow-y: scroll;
    padding: 0 20px 0px 20px;
    height: calc(100% - 150px);
}
 
#chat-container #messageForm {
    padding: 20px;
}

#chat-container ul li {
    line-height: 1.5rem;
    padding: 10px 20px;
    margin: 0;
    border-bottom: 1px solid #f4f4f4;
}

#chat-container ul li p {
    margin: 0;
}

#chat-container .event-message {
    width: 100%;
    text-align: center;
    clear: both;
}

#chat-container .event-message p {
    color: #777;
    font-size: 14px;
    word-wrap: break-word;
}

#chat-container .chat-message {
    position: relative;
}

#messageForm .input-message  {
    float: left;
    width: calc(100% - 85px);
}

.connecting {
    text-align: center;
    color: #777;
    width: 100%;
}

'use strict';


var messageForm = document.querySelector('#messageForm');
var messageInput = document.querySelector('#message');
var messageArea = document.querySelector('#messageArea');
var connectingElement = document.querySelector('#connecting');

var stompClient = null;
var username = null;
 

function connect() {
    username = document.querySelector('#username').innerText.trim();
     
    var socket = new SockJS('/ws');
    stompClient = Stomp.over(socket);

    stompClient.connect({}, onConnected, onError);
}

// Connect to WebSocket Server.
connect();

function onConnected() {
    // Subscribe to the Public Topic
    stompClient.subscribe('/topic/publicChatRoom', onMessageReceived);

    // Tell your username to the server
    stompClient.send("/app/chat.addUser",
        {},
        JSON.stringify({sender: username, type: 'JOIN'})
    )

    connectingElement.classList.add('hidden');
}


function onError(error) {
    connectingElement.textContent = 'Could not connect to WebSocket server. Please refresh this page to try again!';
    connectingElement.style.color = 'red';
}


function sendMessage(event) {
    var messageContent = messageInput.value.trim();
    if(messageContent && stompClient) {
        var chatMessage = {
            sender: username,
            content: messageInput.value,
            type: 'CHAT'
        };
        stompClient.send("/app/chat.sendMessage", {}, JSON.stringify(chatMessage));
        messageInput.value = '';
    }
    event.preventDefault();
}


function onMessageReceived(payload) {
    var message = JSON.parse(payload.body);

    var messageElement = document.createElement('li');

    if(message.type === 'JOIN') {
        messageElement.classList.add('event-message');
        message.content = message.sender + ' joined!';
    } else if (message.type === 'LEAVE') {
        messageElement.classList.add('event-message');
        message.content = message.sender + ' left!';
    } else {
        messageElement.classList.add('chat-message');   
        var usernameElement = document.createElement('strong');
        usernameElement.classList.add('nickname');
        var usernameText = document.createTextNode(message.sender);
        var usernameText = document.createTextNode(message.sender);
        usernameElement.appendChild(usernameText);
        messageElement.appendChild(usernameElement);
    }

    var textElement = document.createElement('span');
    var messageText = document.createTextNode(message.content);
    textElement.appendChild(messageText);

    messageElement.appendChild(textElement);

    messageArea.appendChild(messageElement);
    messageArea.scrollTop = messageArea.scrollHeight;
}
 
 
messageForm.addEventListener('submit', sendMessage, true);