Java应用层协议WebSocket实现消息推送

2023-02-22 12:02:32 协议推送应用层

前言

大部分的web开发者，开发的业务都是基于Http协议的：前端请求后端接口，携带参数，后端执行业务代码，再返回结果给前端。作者参与开发的项目，有一个报警推送的功能，服务端实时推送报警信息给浏览器端；还有像抖音里面，如果有人关注、回复你的评论时，抖音就会推送相关消息给你了，你就会收到一条消息。

有些同学会说了，基于Http协议也能实现啊：前端定时访问后端（每隔3s或者几秒），后端返回消息数据，前端拿到后弹出消息。这种方式太low了，而且每个浏览器都这样，使用系统的人一多，服务器的压力就太大了些。那到底用什么技术手段实现呢？我们的主角就登场了。

websocket是在单个tcp连接上进行全双工通信的应用层协议(Http协议也是应用层)，浏览器端和服务端都可主动发送数据给另一端。这样是不是比Http协议更适合消息推送这种场景。

浏览器端

作者建了一个SpringBoot项目，html放在src\main\resources\static下：

<!DOCTYPE html>
<html lang="zh" xmlns:th="http://www.thymeleaf.org">
<head>
<!--    解决中文乱码-->
    <meta charset="UTF-8"/>
    <title></title>
    <script type="text/javascript" src="./js/Jquery.min.js"></script>
</head>
<body>
    <input id="input1" type="text" /><br/>
    <input type="button" value="浏览器发送服务端" onclick="btnClick()" />
    <input type="button" value="服务端发送浏览器" onclick="btnClick1()" />
    <input type="button" value="重新打开连接" onclick="btnClick2()" />
    <br/>
    <textarea id="textArea" style="height: 50px"></textarea>
<script>
    var ws;
    WEBSocketInit();
    function webSocketInit() {
        ws =new WebSocket('ws://localhost:8080/bootdemo/webSocket/10086');
        // 获取连接状态
        console.log('ws连接状态[初始]：' + ws.readyState);
        //监听是否连接成功
        ws.onopen = function () {
            console.log('ws连接状态[成功]：' + ws.readyState);
        };
        // 接听服务器发回的信息并处理展示
        ws.onmessage = function (obj) {
            console.log('接收到来自服务器的消息：');
            var txt = $("#textArea").val();
            $("#textArea").val(txt + "\n" + obj.data);
            $("#textArea").scrollTop($("#textArea")[0].scrollHeight);
            //完成通信后关闭WebSocket连接
            // ws.close();
        };
        // 监听连接关闭事件
        ws.onclose = function () {
            // 监听整个过程中websocket的状态
            console.log('ws连接状态[关闭]：' + ws.readyState);
        };
        // 监听并处理error事件
        ws.onerror = function (error) {
            console.log(error);
        };
    }
    function btnClick() {
        console.log("浏览器端发送消息：");
        //连接成功则发送一个数据
        ws.send($("#input1").val());
    }
    function btnClick1() {
        $.ajax({
            url: 'http://localhost:8080/bootdemo/pushWebSocket/publish?' +
            'userId=10086&message=' + $("#input1").val(),
            type: 'GET',
            success: function (data) {
                // console.log(data);
            }
        });
    }
    function btnClick2() {
        webSocketInit();
    }
</script>
</body>
</html>

服务器端

先引入依赖：

    <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.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <scope>provided</scope>
    </dependency>

bean上添加@ServerEndpoint，作为WebSocket的服务端。

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArraySet;
@Component
@Slf4j
@ServerEndpoint("/webSocket/{userId}")
public class WebSocketServer {
    //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;
    private static final CopyOnWriteArraySet<WebSocketServer> webSockets =
    new CopyOnWriteArraySet<>();
    // 用来存在线连接数
    private static final Map<String, Session> sessionPool = 
    new HashMap<String, Session>();
    
    @OnOpen
    public void onOpen(Session session, @PathParam(value = "userId") 
    String userId) {
        try {
            this.session = session;
            webSockets.add(this);
            sessionPool.put(userId, session);
        }
        catch (Exception e) {
        }
    }
    
    @OnMessage
    public void onMessage(String message) {
        log.info("websocket消息: 收到客户端消息:" + message);
    }
    public void sendOneMessage(String userId, String message) {
        Session session = sessionPool.get(userId);
        if (session != null && session.isOpen()) {
            try {
                log.info("服务端推送消息：" + message);
                session.getAsyncRemote().sendText(message);
            }
            catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

进行注册：

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

推送消息的控制器：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import java.util.HashMap;
import java.util.Map;
@Controller
@RequestMapping("/pushWebSocket")
public class WebSocketController {
    @Autowired
    private WebSocketServer webSocketServer;
    @GetMapping("/publish")
    @ResponseBody
    public Map publish(String userId, String message) {
        webSocketServer.sendOneMessage(userId, message);
        HashMap<String, Object> map = new HashMap<>();
        map.put("code", 200);
        return map;
    }
}

还有我的配置文件application.properties：

# web port

server.port=8080

server.servlet.context-path=/bootdemo

运行启动类后，访问html(localhost:8080/bootdemo/index.html)如下：

有的同学一思索，点击图中的第2个按钮"服务端发送浏览器"，你这好像也是前端先请求，再推送的消息；我们的WebSocketController#publish方法，在真实的场景下，可以在后端的定时任务中、消息中间件的消费者端调用，不用前端先发送请求。

当然SpringBoot有专门构建WebSocket服务端的方式。

核心配置类：

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerReGIStry;
import org.springframework.web.socket.server.HandshakeInterceptor;
import javax.servlet.http.httpservletRequest;
import java.util.Map;
@Configuration
@EnableWebSocket
@Slf4j
public class WebSocketConfig1 implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry 
    registry) {
        registry.addHandler(new MyWebSocketHandler(), "/webSocket/{userId}")//设置连接路径和处理
                .setAllowedOrigins("*")
                .addInterceptors(new MyWebSocketInterceptor());//设置拦截器
    }
    class MyWebSocketInterceptor implements HandshakeInterceptor {
        //前置拦截一般用来注册用户信息，绑定 WebSocketSession
        @Override
        public boolean beforeHandshake(ServerHttpRequest request, 
        ServerHttpResponse response, WebSocketHandler wsHandler, 
        Map<String, Object> attributes) throws Exception {
            log.info("前置拦截~~");
            if (!(request instanceof ServletServerHttpRequest)) {
                return true;
            }
            HttpServletRequest servletRequest = 
            ((ServletServerHttpRequest)request).getServletRequest();
            Map map = (Map)servletRequest.getAttribute(HandlerMapping.
            URI_TEMPLATE_VARIABLES_ATTRIBUTE);
            String userId = (String)map.get("userId");
            attributes.put("userId", userId);
            return true;
        }
        @Override
        public void afterHandshake(ServerHttpRequest request, 
        ServerHttpResponse response, WebSocketHandler wsHandler, 
        Exception exception) {
            log.info("后置拦截~~");
        }
    }
}

核心处理器：

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.*;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
@Slf4j
@Component
public class MyWebSocketHandler implements WebSocketHandler {
    private static final Map<String, WebSocketSession> SESSIONS = 
    new ConcurrentHashMap<>();
	
    @Override
    public void afterConnectionEstablished(WebSocketSession session) 
    throws Exception {
        String userId = (String) session.getAttributes().get("userId");
        SESSIONS.put(userId, session);
    }
	
    @Override
    public void handleMessage(WebSocketSession session, 
    WebSocketMessage<?> message) throws Exception {
        String msg = message.getPayload().toString();
        log.info("收到客户端消息：" + msg);
    }
	
    @Override
    public void handleTransportError(WebSocketSession session, 
    Throwable exception) throws Exception {
        log.info("连接出错");
        if (session.isOpen()) {
            session.close();
        }
    }
	
    @Override
    public void afterConnectionClosed(WebSocketSession session, 
    CloseStatus closeStatus) throws Exception {
        log.info("连接关闭：status:" + closeStatus);
    }
	
    @Override
    public boolean supportsPartialMessages() {
        return false;
    }
	
    public void sendMessage(String userId, String message) {
        WebSocketSession webSocketSession = SESSIONS.get(userId);
        if (webSocketSession == null || !webSocketSession.isOpen()) {
            return;
        }
        try {
            webSocketSession.sendMessage(new TextMessage(message));
        }
        catch (Exception ex) {
            log.error("推送消息异常：" + ex);
        }
    }
}

控制器也改造下：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import java.util.HashMap;
import java.util.Map;
@Controller
@RequestMapping("/pushWebSocket")
public class WebSocketController {
    @Autowired
    private MyWebSocketHandler handler;
    @GetMapping("/publish")
    @ResponseBody
    public Map publish(String userId, String message) {
        handler.sendMessage(userId, message);
        HashMap<String, Object> map = new HashMap<>();
        map.put("code", 200);
        return map;
    }
}

前端部分不用做修改，和之前一样的代码。

到此这篇关于Java应用层协议WebSocket实现消息推送的文章就介绍到这了,更多相关JAVA WEBSocket内容请搜索以前的文章或继续浏览下面的相关文章希望大家以后多多支持！

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Java应用层协议WebSocket实现消息推送

目录

前言

浏览器端

服务器端