Spring Boot WebSocket 建立一個簡單的網頁聊天室

本篇介紹如何用Spring Boot WebSocket實作一個簡單的網頁聊天室(Chat room)。

本篇內容參考於Building a chat application with Spring Boot and WebSocket。

用Spring Tool Suit(STS)建立一個Spring Boot專案，勾選[WebSocket]

專案剛建立好的目錄結構如下：

專案剛建立好的pom.xml內容：

pom.xml

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>idv.matt</groupId>
    <artifactId>spring-boot-websocket-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-websocket-demo</name>
    <description>Demo project for Spring Boot WebSocket</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <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>

本範例一共用要建立以下檔案

後端：

• WebSocketConfig.java
• ChatMessage.java
• ChatController.java
• WebSocketEventListener.java

前端：

• index.html
• main.css
• main.js

WebSocketConfig是用來配置訊息代理(MessageBroker)的類別，在此要註冊WebSocket的endpoint及設定訊息傳送路徑的prefix。

WebSocketConfig

package idv.matt.demo.config;

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 {
   
    @Override
    public void registerStompEndpoints(StompEndpointRegistry endpointRegistry) {
        // 註冊一個給Client連至WebSocket Server的節點(websocket endpoint)
        endpointRegistry.addEndpoint("/chatroom").withSockJS(); 
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry brokerRegister) {
        
        // 啟用一個訊息代理並設定訊息發送目地的前綴路徑
        brokerRegister.enableSimpleBroker("/topic");
        
        // 設定導向至訊息處理器的前綴路徑
        brokerRegister.setApplicationDestinationPrefixes("/app");
    }

}

ChatMessage為包裝傳輸訊息的容器。

ChatMessage

package idv.matt.demo.message;

/**
 * 傳輸的訊息
 */
public class ChatMessage {
    /** 訊息種類 */
    private ChatType type;
    /** 訊息發送者的名稱 */
    private String sender;
    /** 訊息內容 */
    private String content;

    /**
     * 訊息種類Enum
     */
    public enum ChatType {
        CHAT,
        JOIN,
        LEAVE
    }
    
    // 省略getter setter 
}

ChatController用來接收及發送訊息。@MessageMapping設定前端送來訊息的路徑。@SendTo設定發送訊息給前端的路徑。

ChatController

package idv.matt.demo.controller;

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;

import idv.matt.demo.message.ChatMessage;

/**
 * 接收Client送來的WebSocket訊息及推送給前端的訊息
 */
@Controller
public class ChatController {
    
    /**
     * 處理前端加入聊天室的訊息，並把訊息推送給前端
     */
    @MessageMapping("/join")
    @SendTo("/topic/public")
    public ChatMessage addUser(@Payload ChatMessage chatMessage, 
            SimpMessageHeaderAccessor headerAccessor) {
        // 把username加入WebSocket的Session
        headerAccessor.getSessionAttributes().put("username", chatMessage.getSender());
        return chatMessage; // 返回時會將訊息送至/topic/public
    }
    
    /**
     * 處理前端送來的聊天訊息，並把訊息推送給前端
     */
    @MessageMapping("/chat")
    @SendTo("/topic/public")
    public ChatMessage sendMessage(@Payload ChatMessage chatMessage) {
        return chatMessage; // 返回時會將訊息送至/topic/public
    }

}

WebSocketEventListener負責監聽WebSocket的連線。

WebSocketEventListener

package idv.matt.demo.listener;

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;

import idv.matt.demo.message.ChatMessage;

/**
 * WebSocket連線事件監聽器
 */
@Component
public class WebSocketEventListener {
    
    /** STOMP 訊息發送器 */
    @Autowired
    private SimpMessageSendingOperations messagingTemplate;

    /**
     * 連線時的處理
     */
    @EventListener
    public void handleWebSocketConnectListener(SessionConnectedEvent event) {
        System.out.println("收到一個新的WebSocket連線");
    }
    
    /**
     * 離線時的處理
     */
    @EventListener
    public void handleWebSocketDisconnectListener(SessionDisconnectEvent event) {
        StompHeaderAccessor headerAccessor = StompHeaderAccessor.wrap(event.getMessage());

        // 從WebSocket Session中取得使用者名稱
        String username = (String) headerAccessor.getSessionAttributes().get("username");
        if(username != null) {
            System.out.println("使用者" + username + "已離線");

            // 建立一個離線訊息送給前端
            ChatMessage chatMessage = new ChatMessage();
            chatMessage.setType(ChatMessage.ChatType.LEAVE);
            chatMessage.setSender(username);

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

下面建立前端頁面所需的檔案，先在專案的src/main/resources下建立public資料夾，然後在public資料夾中再建立css及js資料夾

index.html放在public資料夾；
main.css放在css資料夾；
main.js放在js資料夾。

index.html

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Spring Boot WebSocket Chat Application</title>
<link rel="stylesheet" href="/css/main.css" />
</head>
<body>
    <noscript>
        <h2>Sorry! Your browser doesn't support Javascript</h2>
    </noscript>

    <!-- 進入頁面 -->
    <div id="username-page">
        <div class="username-page-container">
            <h1 class="title">輸入名稱</h1>
            
            <form id="usernameForm" name="usernameForm">
                <div class="form-group popup">
                    <input type="text" id="name" placeholder="輸入名稱..."
                        autocomplete="off" class="form-control popup" />
                    <span class="popuptext" id="hint">請輸入名稱</span>
                </div>
                <div class="form-group">
                    <button type="submit" class="accent username-submit">開始聊天</button>
                </div>
            </form>
        </div>
    </div>

    <!-- 聊天室頁面 -->
    <div id="chat-page" class="hidden">
        <div class="chat-container">
            <div class="chat-header">
                <h2>Spring Boot WebSocket Chat Demo</h2>
            </div>
            <div class="connecting">Connecting...</div>
            <ul id="messageArea">

            </ul>
            <form id="messageForm" name="messageForm">
                <div class="form-group">
                    <div class="input-group clearfix">
                        <input type="text" id="message" placeholder="輸入訊息..."
                            autocomplete="off" class="form-control" />
                        <button type="submit" class="primary">送出</button>
                    </div>
                </div>
            </form>
        </div>
    </div>

    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/sockjs-client/1.1.4/sockjs.min.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/stomp.js/2.3.3/stomp.min.js"></script>
    <script type="text/javascript" charset="UTF-8" src="/js/main.js?version=1"></script>
</body>
</html>

main.css

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

html, body {
    height: 100%;
    overflow: hidden;
}

body {
    margin: 0;
    padding: 0;
    font-weight: 400;
    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size: 1rem;
    line-height: 1.58;
    color: #333;
    background-color: #f4f4f4;
    height: 100%;
}

body:before {
    height: 50%;
    width: 100%;
    position: absolute;
    top: 0;
    left: 0;
    background: #008080;
    content: "";
    z-index: 0;
}

.clearfix:after {
    display: block;
    content: "";
    clear: both;
}

.hidden {
    display: none;
}

.form-control {
    width: 100%;
    min-height: 38px;
    font-size: 15px;
    border: 1px solid #c8c8c8;
}

.form-group {
    margin-bottom: 15px;
}

input {
    padding-left: 10px;
    outline: none;
}

h1, h2, h3, h4, h5, h6 {
    margin-top: 20px;
    margin-bottom: 20px;
}

h1 {
    font-size: 1.7em;
}

a {
    color: #128ff2;
}

button {
    box-shadow: none;
    border: 1px solid transparent;
    font-size: 14px;
    outline: none;
    line-height: 100%;
    white-space: nowrap;
    vertical-align: middle;
    padding: 0.6rem 1rem;
    border-radius: 2px;
    transition: all 0.2s ease-in-out;
    cursor: pointer;
    min-height: 38px;
}

button.default {
    background-color: #e8e8e8;
    color: #333;
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.12);
}

button.primary {
    background-color: #128ff2;
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.12);
    color: #fff;
}

button.accent {
    background-color: #ff4743;
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.12);
    color: #fff;
}

#username-page {
    text-align: center;
}

.username-page-container {
    background: #fff;
    box-shadow: 0 1px 11px rgba(0, 0, 0, 0.27);
    border-radius: 2px;
    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;
}

.username-page-container .username-submit {
    margin-top: 10px;
}

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

.chat-container {
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    background-color: #fff;
    box-shadow: 0 1px 11px rgba(0, 0, 0, 0.27);
    margin-top: 30px;
    height: calc(100% - 60px);
    max-height: 600px;
    position: relative;
}

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

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

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

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

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

#chat-page .chat-message {
    padding-left: 68px;
    position: relative;
}

#chat-page .chat-message i {
    position: absolute;
    width: 42px;
    height: 42px;
    overflow: hidden;
    left: 10px;
    display: inline-block;
    vertical-align: middle;
    font-size: 18px;
    line-height: 42px;
    color: #fff;
    text-align: center;
    border-radius: 50%;
    font-style: normal;
    text-transform: uppercase;
}

#chat-page .chat-message span {
    color: #333;
    font-weight: 600;
}

#chat-page .chat-message p {
    color: #43464b;
}

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

#messageForm .input-group button {
    float: left;
    width: 80px;
    height: 38px;
    margin-left: 5px;
}

.chat-header {
    text-align: center;
    padding: 15px;
    border-bottom: 1px solid #ececec;
}

.chat-header h2 {
    margin: 0;
    font-weight: 500;
}

.connecting {
    padding-top: 5px;
    text-align: center;
    color: #777;
    position: absolute;
    top: 65px;
    width: 100%;
}

@media screen and (max-width: 730px) {
    .chat-container {
        margin-left: 10px;
        margin-right: 10px;
        margin-top: 10px;
    }
}

@media screen and (max-width: 480px) {
    .chat-container {
        height: calc(100% - 30px);
    }
    .username-page-container {
        width: auto;
        margin-left: 15px;
        margin-right: 15px;
        padding: 25px;
    }
    #chat-page ul {
        height: calc(100% - 120px);
    }
    #messageForm .input-group button {
        width: 65px;
    }
    #messageForm .input-group input {
        width: calc(100% - 70px);
    }
    .chat-header {
        padding: 10px;
    }
    .connecting {
        top: 60px;
    }
    .chat-header h2 {
        font-size: 1.1em;
    }
}

/* Popup container */
.popup {
  position: relative;
}
/* The actual popup (appears on top) */
.popup .popuptext {
    visibility: hidden;
    width: 160px;
    background-color: #ff8080;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 8px 0;
    position: absolute;
    z-index: 1;
    bottom: 125%;
    left: 10%;
    margin-left: -80px;
}

/* Popup arrow */
.popup .popuptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #ff8080 transparent transparent transparent;
}

/* Toggle this class when clicking on the popup container (hide and show the popup) */
.popup .show {
    visibility: visible;
    -webkit-animation: fadeIn 0.5s;
    animation: fadeIn 0.5s
}

/* Add animation (fade in the popup) */
@-webkit-keyframes fadeIn {
    from {opacity: 0;} 
    to {opacity: 1;}
}

@keyframes fadeIn {
    from {opacity: 0;}
    to {opacity:1 ;}
}

main.js

'use strict';

var usernamePage = document.querySelector('#username-page');
var chatPage = document.querySelector('#chat-page');
var usernameForm = document.querySelector('#usernameForm');
var messageForm = document.querySelector('#messageForm');
var messageInput = document.querySelector('#message');
var messageArea = document.querySelector('#messageArea');
var connectingElement = document.querySelector('.connecting');
var nameInput = document.querySelector('#name');
var popup = document.querySelector('#hint');

var stompClient = null;
var username = null;

/**
 * 頭像的顏色
 */
var colors = [ '#2196F3', '#32c787', '#00bcd4','#4dbb00', '#ff5652', '#ffc107',
        '#ff85af', '#ff9800', '#39bbb0', '#b0c503' ];

/**
 * 連線
 * @param event
 * @returns
 */
function connect(event) {
    username = document.querySelector('#name').value.trim();

    if (username) {
        usernamePage.classList.add('hidden');
        chatPage.classList.remove('hidden');

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

        stompClient.connect({}, onConnected, onError);
    } else {
        popHint();
    }
    event.preventDefault();
}

/**
 * 連線建立後要處理的邏輯
 * @returns
 */
function onConnected() {
    // 訂閱/topic/public
    stompClient.subscribe('/topic/public', onMessageReceived); // 當後端送訊息至/topic/public時，會執行onMessageReceived()。

    // 發送訊息至/app/join，也就是送到ChatController.addUser()
    stompClient.send("/app/join", {}, 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';
}

/**
 * 彈出提示
 * @returns
 */
function popHint() {
    popup.classList.toggle("show");
}

/**
 * 發送訊息
 * @param event 發送訊息事件
 * @returns
 */
function sendMessage(event) {
    var messageContent = messageInput.value.trim();
    if (messageContent && stompClient) {
        var chatMessage = {
            sender : username,
            content : messageInput.value,
            type : 'CHAT'
        };
        // 發送訊息至/app/chat，也就是送到ChatController.sendMessage()
        stompClient.send("/app/chat", {}, JSON.stringify(chatMessage));
        messageInput.value = '';
    }
    event.preventDefault();
}

/**
 * 從後端接受訊息後要進行的處理
 * @param payload 後端送來的訊息
 * @returns
 */
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 + ' 加入聊天室';
    } else if (message.type === 'LEAVE') {
        messageElement.classList.add('event-message');
        message.content = message.sender + ' 離開聊天室';
    } else {
        messageElement.classList.add('chat-message');

        var avatarElement = getAvatarElement(message.sender);
        messageElement.appendChild(avatarElement);

        var usernameElement = getUsernameElement(message.sender);
        messageElement.appendChild(usernameElement);
    }

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

    messageElement.appendChild(textElement);

    messageArea.appendChild(messageElement);
    messageArea.scrollTop = messageArea.scrollHeight;
}

/**
 * 取得頭像元素
 * @param sender 訊息發送者名稱
 * @returns
 */
function getAvatarElement(sender) {
    var avatarElement = document.createElement('i');
    var avatarText = document.createTextNode(sender[0]);
    avatarElement.appendChild(avatarText);
    avatarElement.style['background-color'] = getAvatarColor(sender);
    return avatarElement;
}

/**
 * 取得頭像顏色
 * @param sender 訊息發送者名稱
 * @returns
 */
function getAvatarColor(sender) {
    var hash = 0;
    for (var i = 0; i < sender.length; i++) {
        hash = 31 * hash + sender.charCodeAt(i);
    }
    var index = Math.abs(hash % colors.length);
    return colors[index];
}

/**
 * 取得使用者名稱的元素
 * @param sender 使用者名稱
 * @returns
 */
function getUsernameElement(sender) {
    var usernameElement = document.createElement('span');
    var usernameText = document.createTextNode(sender);
    usernameElement.appendChild(usernameText);
    return usernameElement;
}

/**
 * 移除彈出的提示
 * @param event
 * @returns
 */
function removePopup (event) {
    popup.classList.remove("show");
}

nameInput.addEventListener('focus', removePopup, true)
usernameForm.addEventListener('submit', connect, true)
messageForm.addEventListener('submit', sendMessage, true)

完成後的目錄結構如下：

然後啟動Spring Boot專案，在瀏覽器輸入http://localhost:8080/即可進入畫面。

如果本篇有幫助到您，幫忙點一下廣告支持，感恩。

• Building a chat application with Spring Boot and WebSocket
• Using WebSocket to build an interactive web application
• Spring Doc - WebSockets
• Stomp - The Simple Text Oriented Messaging Protocol
• MDN Web docs - The WebSocket API (WebSockets)
• sockjs/sockjs-client
• STOMP.js
• STOMP Over WebSocket