一、websocket介绍

WebSocket 是一种基于 TCP 协议的全双工通信协议，它允许客户端和服务器之间建立持久的、双向的通信连接。相比传统的 HTTP 请求 - 响应模式，WebSocket 提供了实时、低延迟的数据传输能力。通过 WebSocket，客户端和服务器可以在任意时间点互相发送消息，实现实时更新和即时通信的功能。WebSocket 协议经过了多个浏览器和服务器的支持，成为了现代 Web 应用中常用的通信协议之一。它广泛应用于聊天应用、实时数据更新、多人游戏等场景，为 Web 应用提供了更好的用户体验和更高效的数据传输方式。

二、代码工程

本实验将会指导你如何在 Spring Boot 中整合、使用 WebSocket

maven依赖

<?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">    <parent>        <artifactId>springboot-demo</artifactId>        <groupId>com.et</groupId>        <version>1.0-SNAPSHOT</version>    </parent>    <modelVersion>4.0.0</modelVersion>
    <artifactId>websocket</artifactId>
    <properties>        <maven.compiler.source>8</maven.compiler.source>        <maven.compiler.target>8</maven.compiler.target>    </properties>    <dependencies>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-autoconfigure</artifactId>        </dependency>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-websocket</artifactId>        </dependency>        <dependency>            <groupId>com.alibaba</groupId>            <artifactId>fastjson</artifactId>            <version>2.0.40</version>            <scope>compile</scope>        </dependency>    </dependencies></project>

配置文件

server:  port: 8088

websocket配置类

package com.et.websocket.config;
import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.web.socket.config.annotation.EnableWebSocket;import org.springframework.web.socket.server.standard.ServerEndpointExporter;
@Configuration@EnableWebSocketpublic class WebSocketConfiguration {
    @Bean    public ServerEndpointExporter serverEndpointExporter() {        return new ServerEndpointExporter();    }}

websocket服务类

WebSocket 一共有四个事件，分别对应 JSR-356 定义的 @OnOpen、@OnMessage、@OnClose、@OnError 注解。

@OnOpen：标注客户端打开 WebSocket 服务端点调用方法
@OnClose：标注客户端关闭 WebSocket 服务端点调用方法
@OnMessage：标注客户端发送消息，WebSocket 服务端点调用方法
@OnError：标注客户端请求 WebSocket 服务端点发生异常调用方法

package com.et.websocket.channel;
import com.alibaba.fastjson2.JSON;import com.alibaba.fastjson2.JSONObject;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Component;import org.springframework.util.StringUtils;
import javax.websocket.*;import javax.websocket.server.PathParam;import javax.websocket.server.ServerEndpoint;import java.io.IOException;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.atomic.AtomicInteger;
@ServerEndpoint("/websocket/{userId}")@Componentpublic class WebSocketServer {
    private static final Logger log = LoggerFactory.getLogger(WebSocketServer.class);
    /**     * 当前在线连接数     */    private static AtomicInteger onlineCount = new AtomicInteger(0);
    /**     * 用来存放每个客户端对应的 WebSocketServer 对象     */    private static ConcurrentHashMap<String, WebSocketServer> webSocketMap = new ConcurrentHashMap<>();
    /**     * 与某个客户端的连接会话，需要通过它来给客户端发送数据     */    private Session session;
    /**     * 接收 userId     */    private String userId = "";
    /**     * 连接建立成功调用的方法     */    @OnOpen    public void onOpen(Session session, @PathParam("userId") String userId) {        this.session = session;        this.userId = userId;        if (webSocketMap.containsKey(userId)) {            webSocketMap.remove(userId);            webSocketMap.put(userId, this);        } else {            webSocketMap.put(userId, this);            addOnlineCount();        }        log.info("用户连接:" + userId + ",当前在线人数为:" + getOnlineCount());        try {            sendMessage("连接成功！");        } catch (IOException e) {            log.error("用户:" + userId + ",网络异常!!!!!!");        }    }
    /**     * 连接关闭调用的方法     */    @OnClose    public void onClose() {        if (webSocketMap.containsKey(userId)) {            webSocketMap.remove(userId);            subOnlineCount();        }        log.info("用户退出:" + userId + ",当前在线人数为:" + getOnlineCount());    }
    /**     * 收到客户端消息后调用的方法     *     * @param message 客户端发送过来的消息     */    @OnMessage    public void onMessage(String message, Session session) {        log.info("用户消息:" + userId + ",报文:" + message);        if (!StringUtils.isEmpty(message)) {            try {                JSONObject jsonObject = JSON.parseObject(message);                jsonObject.put("fromUserId", this.userId);                String toUserId = jsonObject.getString("toUserId");                if (!StringUtils.isEmpty(toUserId) && webSocketMap.containsKey(toUserId)) {                    webSocketMap.get(toUserId).sendMessage(jsonObject.toJSONString());                } else {                    log.error("请求的 userId:" + toUserId + "不在该服务器上");                }            } catch (Exception e) {                e.printStackTrace();            }        }    }
    /**     * 发生错误时调用     *     * @param session     * @param error     */    @OnError    public void onError(Session session, Throwable error) {        log.error("用户错误:" + this.userId + ",原因:" + error.getMessage());        error.printStackTrace();    }
    /**     * 实现服务器主动推送     */    public void sendMessage(String message) throws IOException {        this.session.getBasicRemote().sendText(message);    }
    public static synchronized AtomicInteger getOnlineCount() {        return onlineCount;    }
    public static synchronized void addOnlineCount() {        WebSocketServer.onlineCount.getAndIncrement();    }
    public static synchronized void subOnlineCount() {        WebSocketServer.onlineCount.getAndDecrement();    }}

启动类

package com.et.websocket;
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplicationpublic class DemoApplication {
   public static void main(String[] args) {      SpringApplication.run(DemoApplication.class, args);   }}

代码仓库

https://github.com/Harries/springboot-demo

三、测试

打开postman，新建2个websocket测试连接，ws://127.0.0.1:8088/websocket/wupx，点击开启连接按钮，消息记录中会多一条由服务器端发送的连接成功！记录。输入ws://127.0.0.1:8088/websocket/huxy，点击开启连接按钮，然后回到第一次打开的网页在消息框中输入{"toUserId":"huxy","message":"i love you"}，点击发送到服务端，第二个网页中会收到服务端推送的消息{"fromUserId":"wupx","message":"i love you","toUserId":"huxy"}。控制台输出

2024-02-26 15:26:48.699 INFO 27848 --- [nio-8088-exec-2] c.et.websocket.channel.WebSocketServer : 用户连接:huxy,当前在线人数为:12024-02-26 15:26:56.581 INFO 27848 --- [nio-8088-exec-4] c.et.websocket.channel.WebSocketServer : 用户连接:wupx,当前在线人数为:22024-02-26 15:27:26.401 INFO 27848 --- [nio-8088-exec-5] c.et.websocket.channel.WebSocketServer : 用户消息:wupx,报文:{"toUserId":"huxy","message":"i love you"}

四、引用

https://www.cnblogs.com/wupeixuan/p/13389757.html
http://www.liuhaihua.cn/archives/710240.html

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