springboot+websocket简单使用

一、引入依赖

<?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 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>2.7.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo1</name>
    <description>demo1</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</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>

二、config配置

package com.example.demo.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

/**
 * WebSocket配置
 *
 * @author caozz
 * @since 2023/6/20 16:30
 */
@Configuration
public class WebSocketConfig {

    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }

}

三、WebSocketServer

package com.example.demo.config;

import org.springframework.stereotype.Component;

import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;

/**
 * websocket server服务
 *
 * @author caozz
 * @since 2023/6/20 16:40
 */
@ServerEndpoint("/{userId}")
@Component
public class WebSocketServer {

    private static int onlineCount = 0;     // 在线人数
    public static ConcurrentHashMap<String,WebSocketServer> webSocketMap = new ConcurrentHashMap<>();   // session管理map
    private Session session;    // 会话session
    private String userId="";   // 当前用户

    /**
     * 初始化连接
     *
     * @param session 会话session
     * @param userId 当前用户id
     */
    @OnOpen
    public void onOpen(Session session, @PathParam("userId") String userId) {
        System.out.println("客户端："+userId+"连接成功");
        this.session = session;
        this.userId=userId;

        // 保存各用户的会话session
        if(webSocketMap.containsKey(userId)){
            webSocketMap.remove(userId);
            webSocketMap.put(userId, this);
        }else{
            webSocketMap.put(userId, this);
            addOnlineCount();
        }

        try {
            sendMessage(userId + " connect success!");
        } catch (IOException e) {

        }
    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose() {
        System.out.println("连接已经关闭了,");
        if(webSocketMap.containsKey(userId)){
            webSocketMap.remove(userId);
            subOnlineCount();
        }
    }

    /**
     * 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) {
        System.out.println("来自客户端的消息："+message);
        //返回消息给客户端
        try {
            // session 就是客户端和服务器自连接起来建立的会话
            // 直到关闭连接直接这个会话一直是连接的，所以我们在这个过程中可以用它给客户端推送消息
            session.getBasicRemote().sendText("client,I have received your message");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 异常处理
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        System.out.println("System Error！msg:" + error);
        error.printStackTrace();
    }

    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }

    /**
     * 发送自定义消息
     *
     * @param message 消息体
     * */
    public void sendInfo(String message) throws IOException {

        List<String> keys = new ArrayList<>(webSocketMap.keySet());

            for (String key : keys) {
                webSocketMap.get(key).sendMessage(message);
            }

    }

    public static synchronized int getOnlineCount() {
        return onlineCount;
    }

    public static synchronized void addOnlineCount() {
        WebSocketServer.onlineCount++;
    }

    public static synchronized void subOnlineCount() {
        WebSocketServer.onlineCount--;
    }
}

四、推送消息

这里不一定要访问接口，也可以服务端监听数据变化，或者数据入库时触发

package com.example.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import static com.example.demo.config.WebSocketServer.webSocketMap;

/**
 * @Author: caozhouzhou
 * @Date: 2023/6/20 16:53
 **/
@RestController
public class HelloWorld {

    @GetMapping("/hello")
    public String hello() throws Exception {
        for (String userId:webSocketMap.keySet()) {
            webSocketMap.get(userId).sendMessage("我是服务端，现在广播推送一条消息。。。");
        }
        return "SUCCESS";
    }
}