WebSocket简单介绍

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WebSocket 是什么

阮一峰老师有过一篇博文清晰易懂地介绍了 WebSocket

下面主要通过一个例子介绍 WebSocket 在 Spring中是如何使用的.

前端代码

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>

    <!-- 播放音乐 -->
    <audio id="notice" loop="loop">
        <source src="music.m4a" type="audio/mp4">
    </audio>

    <script>
        var websocket = null;
        if('WebSocket' in window) {
            websocket = new WebSocket('ws://localhost:8080/webSocket');
        } else {
            alert('该浏览器不支持WebSocket!');
        }

        websocket.onopen = function (event) {
            console.log('建立连接');
            websocket.send("Hello, WebSocket! 来自客户端");
        }

        websocket.onclose = function (event) {
            console.log('连接关闭');
        }

        websocket.onmessage = function (event) {
            console.log('收到消息: ' + event.data);
            // 播放音乐, 提醒消息
            document.getElementById("notice").play();

            setTimeout(function() {
                document.getElementById("notice").pause();
            }, 2000);
        }


        websocket.onerror = function () {
            alert('websocket通信发生错误!');
        }

        websocket.onbeforeunload = function () {
            websocket.close();
        }
    </script>
</body>
</html>

后端主要代码(SpringBoot)

其中主要依赖如下

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<dependencies>
    <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.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

WebSocketConfig.java
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package com.example.websocket_demo.config;

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

@Component
public class WebSocketConfig {

    @Bean
    public ServerEndpointExporter serverEndpointConfig() {
        return new ServerEndpointExporter();
    }
}
WebSocket.java
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package com.example.websocket_demo.service;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import java.util.concurrent.CopyOnWriteArraySet;

@Component
@ServerEndpoint("/webSocket")
@Slf4j
public class WebSocket {

    private Session session;

    private static CopyOnWriteArraySet<WebSocket> webSocketSet = new CopyOnWriteArraySet<>();

    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        webSocketSet.add(this);
        log.info("[webSocket消息] 有新的连接, 总数: {}", webSocketSet.size());
    }

    @OnClose
    public void onClose() {
        webSocketSet.remove(this);
        log.info("[webSocket消息] 连接断开, 总数: {}", webSocketSet.size());
    }

    @OnMessage
    public void onMessage(String message) {
        log.info("[webSocket消息] 收到客户端发来的消息: {}", message);
    }

    public void sendMessage(String message) {
        for (WebSocket webSocket: webSocketSet) {
            log.info("[webSocket消息] 广播消息, message={}", message);
            try {
                webSocket.session.getBasicRemote().sendText(message);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}
MainController.java
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package com.example.websocket_demo.controller;

import com.example.websocket_demo.service.WebSocket;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MainController {

    @Autowired
    private WebSocket webSocket;

    @GetMapping("/testWebSocket")
    public String testWebSocket() {
        webSocket.sendMessage("有新的订单!");
        return "ok";
    }
}

效果展示

如下图所示, 在我们访问 /testWebSocket 后, 会有一条消息从服务端发送到我们的前端页面