SpringBoot+WebSocket实现即时通讯（Spring方式）

2022-10-24

本文最后更新于2023.04.22-17:45，某些文章具有时效性，若有错误或已失效，请在下方留言或联系涛哥。

前言

最近由于一些原因很久没写文章了，今天给大家分享一个Spring方式使用ws长连接实现简单聊天室功能

什么是websocket？

WebSocket是一种在单个TCP连接上进行全双工通信的协议。WebSocket通信协议于2011年被IETF定为标准RFC 6455，并由RFC7936补充规范。WebSocket API也被W3C定为标准。
WebSocket使得客户端和服务器之间的数据交换变得更加简单，允许服务端主动向客户端推送数据。在WebSocket API中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输。

为什么有了HTTP协议还要WebSocket

HTTP协议采用的是客户端（浏览器）轮询的方式，即客户端发送请求，服务端做出响应，为了获取最新的数据，需要不断的轮询发出HTTP请求，占用大量带宽。
WebSocket采用了一些特殊的报头，使得浏览器和服务器只需要通过“握手”建立一条连接通道后，此链接保持活跃状态，之后的客户端和服务器的通信都使用这个连接，解决了Web实时性的问题，相比于HTTP有一下好处：

一个Web客户端只建立一个TCP连接
WebSocket服务端可以主动推送（push）数据到Web客户端
有更加轻量级的头，减少了数据传输量

特点

建立在TCP协议只上，服务端比较容易实现
于HTTP协议有良好的兼容性，默认端口也是80和443，握手阶段使用HTTP协议，因此握手时不容易屏蔽，能通过各种HTTP代理服务器
数据格式轻量，通信高效且节省带宽
支持传输文本数据和二进制数据
没有同源限制，客户端可以与任意服务器通信
也支持加密传输，WS+SSL，URL形如wss://

技术

jdk8
maven
SpringBoot2.7.4
thmeleaf
websocket

实现（简易websocket聊天室）

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 https://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>2.7.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>websocket</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>websocket</name>
    <description>websocket</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>

websocketHandler.java

package com.example.websocket.handler;


import org.springframework.stereotype.Component;
import org.springframework.web.socket.*;

import java.io.IOException;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

@Component
public class WebsocketHandler implements WebSocketHandler {

    private static final Map<String, WebSocketSession> SESSIONS = new ConcurrentHashMap<>();
    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        System.out.println("连接成功"+session.getId());
        SESSIONS.put(session.getId(), session);
        System.out.println("当前在线人数："+SESSIONS.size());
    }

    @Override
    public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {
        System.out.println("接收消息"+session.getId());
        String msg = message.getPayload().toString();
        System.out.println(msg);
//        session.sendMessage(message);
        sendMessageToAllUsers(session.getId()+":"+msg);
    }

    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        System.out.println("连接出错"+session.getId());
        if (!session.isOpen()) {
            SESSIONS.remove(session.getId());
            session.close();
        }
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {
        System.out.println("关闭连接"+session.getId());
        if(!session.isOpen()){
            SESSIONS.remove(session.getId());
            System.out.println("当前在线人数："+SESSIONS.size());
        }
    }

    @Override
    public boolean supportsPartialMessages() {
        return false;
    }

    /**
     * sendMessageToUser:发给指定用户
     *
     */
    public void sendMessageToUser(String userId, String contents) {
        WebSocketSession session = SESSIONS.get(userId);
        if (session != null && session.isOpen()) {
            try {
                TextMessage message = new TextMessage(contents);
                session.sendMessage(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * sendMessageToAllUsers:发给所有的用户
     *
     */
    public void sendMessageToAllUsers(String contents) {
        Set<String> userIds = SESSIONS.keySet();
        for (String userId : userIds) {
            this.sendMessageToUser(userId, contents);
        }
    }
}

WebsocketInterceptor.java

package com.example.websocket.interceptor;

import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.HandshakeInterceptor;

import java.util.Map;

@Component
public class WebsocketInterceptor implements HandshakeInterceptor {
    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
        System.out.println("前置拦截");
        return true;
    }

    @Override
    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception exception) {
        System.out.println("后置拦截");
    }
}

WebsocketConfig.java

package com.example.websocket.config;

import com.example.websocket.handler.WebsocketHandler;
import com.example.websocket.interceptor.WebsocketInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;

@Component
@EnableWebSocket
public class WebsocketConfig implements WebSocketConfigurer {
    @Autowired
    private  WebsocketHandler websocketHandler;
    @Autowired
    private WebsocketInterceptor websocketInterceptor;

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(websocketHandler, "/ws").setAllowedOrigins("*").addInterceptors(websocketInterceptor);
    }
}

WebsocketController.java

package com.example.websocket.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class WebsocketController {

    @GetMapping("/")
    public String init() {
        return "websocket";
    }

    @GetMapping("/chat")
    public String chat() {
        return "chatRoom";
    }
}

WebsocketApplication.java

package com.example.websocket;

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

@SpringBootApplication
public class WebsocketApplication {

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

}

前端

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>My WebSocket Test</title>
    <!-- 最新版本的 Bootstrap 核心 CSS 文件 -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">

    <!-- 可选的 Bootstrap 主题文件（一般不用引入） -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap-theme.min.css" integrity="sha384-6pzBo3FDv/PJ8r2KRkGHifhEocL+1X2rVCTTkUfGk7/0pbek5mMa1upzvWbrUbOZ" crossorigin="anonymous">

    <!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js" integrity="sha384-aJ21OjlMXNL5UyIl/XNwTMqvzeRMZH2w8c5cRVpzpU8Y5bApTppSuUkhZXN0VxHd" crossorigin="anonymous"></script>
</head>
<body>

Welcome<br/>
<div id="message"></div>
<input id="text" type="text" />
<button class="btn btn-primary" onclick="send()">Send</button>
<button class="btn btn-danger"onclick="closeWebSocket()">Close</button>
</body>

<script type="text/javascript">

    var websocket = null;

    //判断当前浏览器是否支持WebSocket
    if('WebSocket' in window){
        websocket = new WebSocket("ws://localhost:8080/ws");
    }
    else{
        alert('Not support websocket')
    }

    //连接发生错误的回调方法
    websocket.onerror = function(){
        setMessageInnerHTML("error");
    };

    //连接成功建立的回调方法
    websocket.onopen = function(event){
        setMessageInnerHTML("open");
    }

    //接收到消息的回调方法
    websocket.onmessage = function(event){
        setMessageInnerHTML(event.data);
    }

    //连接关闭的回调方法
    websocket.onclose = function(){
        setMessageInnerHTML("close");
    }

    //监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
    window.onbeforeunload = function(){
        websocket.close();
    }

    //将消息显示在网页上
    function setMessageInnerHTML(innerHTML){
        document.getElementById('message').innerHTML += innerHTML + '<br/>';
    }

    //关闭连接
    function closeWebSocket(){
        websocket.close();
    }

    //发送消息
    function send(){
        var message = document.getElementById('text').value;
        websocket.send(message);
        message.value("");
    }
</script>
</html>