Spring Boot + Vue3 实时对战系统：WebSocket 匹配与 JWT 验证实战

引言

在现代 Web 开发中，前端和后端的协作至关重要，特别是在需要实时交互和数据更新的应用场景下。WebSocket 作为一种全双工通信协议，让前后端之间的实时数据传输更加高效稳定。本文将探讨如何设计和实现一个实时匹配系统，前端负责展示用户界面并与后端交互，后端则通过 WebSocket 协议处理数据通信。

前端状态管理

在 Vue3 项目中，我们需要用 Vuex 来维护全局的 WebSocket 连接和匹配状态。这里定义了一个 pk 模块，用来存储 socket 实例、对手信息以及当前是匹配中还是对战中的状态。

store/pk.js:

import ModuleUser from './user'
export default {
  state: {
    socket: null, // ws 链接
    opponent_username: "",
    opponent_photo: "",
    status: "matching", // matching 表示匹配界面，playing 表示对战界面
  },
  getters: {},
  mutations: {
    updateSocket(state, socket) { state.socket = socket; },
    updateOpponent(state, opponent) {
      state.opponent_username = opponent.username;
      state.opponent_photo = opponent.photo;
    },
    updateStatus(state, status) { state.status = status; }
  },
  actions: {},
  modules: {
    user: ModuleUser,
  }
}

记得在 store/index.js 中引入这个模块：

import { createStore } from 'vuex'
import ModuleUser from './user'
import ModulePk from './pk'
export default createStore({
  state: {},
  getters: {},
  mutations: {},
  actions: {},
  modules: {
    user: ModuleUser,
    pk: ModulePk,
  }
})

建立 WebSocket 连接

在前端页面中，我们使用 Vue 的生命周期钩子来管理连接的建立和销毁。这里要注意，URL 拼接时要用反引号，方便嵌入变量。

views/pk/PKIndex.vue:

<template>
  <PlayGround/>
</template>
<script>
import PlayGround from '@/components/PlayGround.vue'
import { onMounted, onUnmounted } from 'vue'
import { useStore } from 'vuex'

export default {
  name: 'PKindex',
  components: { PlayGround },
  setup() {
    const store = useStore()
    // 注意：实际生产环境建议替换为 token 验证
    const socketUrl = `ws://127.0.0.1:3000/websocket/${store.state.user.id}/`
    let socket = null

    onMounted(() => {
      socket = new WebSocket(socketUrl)
      socket.onopen = () => {
        console.log('connected!')
        store.commit('updateSocket', socket)
      }
      socket.onmessage = msg => {
        const data = JSON.parse(msg.data)
        console.log(data)
      }
      socket.onclose = () => {
        console.log('disconnected!')
      }
    })

    onUnmounted(() => {
      if (socket) socket.close()
    })
  }
}
</script>
<style scoped></style>

到这里，前端已经能和后端建立基础连接了。不过直接用 userId 做路径参数存在安全隐患，用户可能伪装成任意 ID。接下来我们加上 JWT 验证。

安全升级：JWT 验证

修改连接 URL，将 userId 换成 token。后端接收到 token 后解析出用户 ID，如果无效直接关闭连接。

consumer/utils/JwtAuthentication.java:

package org.example.backend.consumer.utils;
import io.jsonwebtoken.Claims;
import org.example.backend.utils.JwtUtil;

public class JwtAuthentication {
    public static Integer getUserId(String token) {
        int userId = -1; // -1 表示不存在
        try {
            Claims claims = JwtUtil.parseJWT(token);
            userId = Integer.parseInt(claims.getSubject());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return userId;
    }
}

后端 WebSocketServer 也需要相应调整：

@OnOpen
public void onOpen(Session session, @PathParam("token") String token) throws IOException {
    this.session = session;
    System.out.println("connected to websocket");
    Integer userId = JwtAuthentication.getUserId(token);
    this.user = userMapper.selectById(userId);
    
    if (user != null) {
        users.put(userId, this);
    } else {
        this.session.close(); // 验证失败直接断开
    }
}

匹配逻辑实现

前端界面切换

我们需要根据状态动态渲染'匹配界面'或'对战界面'。

views/pk/PKIndexView.vue:

<template>
  <PlayGround v-if="$store.state.pk.status === 'playing'"/>
  <MatchGround v-if="$store.state.pk.status === 'matching'"/>
</template>

匹配组件设计

匹配界面用 Grid 布局，左右各显示一个头像，中间放按钮。点击按钮发送 WebSocket 消息通知后端。

components/MatchGround.vue:

<template>
  <div class="matchground">
    <div class="row">
      <div class="col-6">
        <div class="user-photo"><img :src="$store.state.user.photo" alt=""></div>
        <div class="user-username">{{ $store.state.user.username }}</div>
      </div>
      <div class="col-6">
        <div class="user-photo"><img :src="$store.state.pk.opponent_photo" alt=""></div>
        <div class="user-username">{{ $store.state.pk.opponent_username }}</div>
      </div>
      <div class="col-12" style="text-align: center; padding-top: 15vh;">
        <button @click="click_match_btn" type="button" class="btn btn-warning btn-lg">
          {{ match_btn_info }}
        </button>
      </div>
    </div>
  </div>
</template>
<script>
import { ref } from 'vue'
import { useStore } from 'vuex';

export default {
  setup() {
    const store = useStore();
    let match_btn_info = ref("开始匹配");

    const click_match_btn = () => {
      if (match_btn_info.value === "开始匹配") {
        match_btn_info.value = "取消";
        store.state.pk.socket.send(JSON.stringify({ event: "start-matching" }));
      } else {
        match_btn_info.value = "开始匹配";
        store.state.pk.socket.send(JSON.stringify({ event: "stop-matching" }));
      }
    }
    return { match_btn_info, click_match_btn };
  }
}
</script>
<style scoped>
div.matchground { width: 60vw; height: 70vh; margin: 40px auto; background-color: rgba(50,50,50,0.5); }
div.user-photo { text-align: center; padding-top: 10vh; }
div.user-photo > img { border-radius: 50%; width: 20vh; }
div.user-username { text-align: center; font-size: 24px; font-weight: 600; color: white; padding-top: 2vh; }
</style>

后端匹配池处理

后端维护一个线程安全的匹配池 matchpool。当收到 start-matching 消息时加入池子，如果池子里有两人，就配对成功并创建游戏。

consumer/WebSocketServer.java:

@Component
@ServerEndpoint("/websocket/{token}")
public class WebSocketServer {
    final private static ConcurrentHashMap<Integer, WebSocketServer> users = new ConcurrentHashMap<>();
    final private static CopyOnWriteArraySet<User> matchpool = new CopyOnWriteArraySet<>();
    private User user;
    private Session session = null;
    private static UserMapper userMapper;

    @Autowired
    public void setUserMapper(UserMapper userMapper) {
        WebSocketServer.userMapper = userMapper;
    }

    @OnOpen
    public void onOpen(Session session, @PathParam("token") String token) throws IOException {
        this.session = session;
        Integer userId = JwtAuthentication.getUserId(token);
        this.user = userMapper.selectById(userId);
        if (this.user != null) {
            users.put(userId, this);
        } else {
            this.session.close();
        }
    }

    @OnClose
    public void onClose() {
        if (this.user != null) {
            users.remove(this.user.getId());
            matchpool.remove(this.user);
        }
    }

    private void startMatching() {
        matchpool.add(this.user);
        while (matchpool.size() >= 2) {
            Iterator<User> it = matchpool.iterator();
            User a = it.next(), b = it.next();
            matchpool.remove(a);
            matchpool.remove(b);
            Game game = new Game(13, 14, 20);
            game.createMap();
            JSONObject respA = new JSONObject();
            respA.put("event", "start-matching");
            respA.put("opponent_username", b.getUsername());
            respA.put("opponent_photo", b.getPhoto());
            respA.put("gamemap", game.getG());
            users.get(a.getId()).sendMessage(respA.toJSONString());

            JSONObject respB = new JSONObject();
            respB.put("event", "start-matching");
            respB.put("opponent_username", a.getUsername());
            respB.put("opponent_photo", a.getPhoto());
            respB.put("gamemap", game.getG());
            users.get(b.getId()).sendMessage(respB.toJSONString());
        }
    }

    private void stopMatching() {
        matchpool.remove(this.user);
    }

    @OnMessage
    public void onMessage(String message, Session session) {
        JSONObject data = JSONObject.parseObject(message);
        String event = data.getString("event");
        if ("start-matching".equals(event)) {
            startMatching();
        } else if ("stop-matching".equals(event)) {
            stopMatching();
        }
    }

    public void sendMessage(String message) {
        synchronized (this.session) {
            try {
                this.session.getBasicRemote().sendText(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

前端收到匹配成功的消息后，更新对手信息和地图，然后切换到对战状态：

socket.onmessage = msg => {
  const data = JSON.parse(msg.data);
  if (data.event === "start-matching") {
    store.commit("updateOpponent", {
      username: data.opponent_username,
      photo: data.opponent_photo,
    });
    setTimeout(() => {
      store.commit("updateStatus", "playing");
    }, 2000);
    store.commit("updateGamemap", data.gamemap);
  }
};

游戏地图生成算法

为了增加游戏的可玩性，我们需要在后端生成随机地图。这里用 Java 复用了之前前端的 DFS 迷宫生成逻辑。

consumer/utils/Game.java:

package org.example.backend.consumer.utils;
import java.util.Random;

public class Game {
    final private Integer rows;
    final private Integer cols;
    final private Integer inner_walls_count;
    final private int[][] g;
    final private static int[] dx = {-1, 0, 1, 0}, dy = {0, 1, 0, -1};

    public Game(Integer rows, Integer cols, Integer inner_walls_count) {
        this.rows = rows;
        this.cols = cols;
        this.inner_walls_count = inner_walls_count;
        this.g = new int[rows][cols];
    }

    public int[][] getG() {
        return g;
    }

    private boolean check_connectivity(int sx, int sy, int tx, int ty) {
        if (sx == tx && sy == ty) return true;
        g[sx][sy] = 1;
        for (int i = 0; i < 4; i++) {
            int x = sx + dx[i], y = sy + dy[i];
            if (x >= 0 && x < this.rows && y >= 0 && y < this.cols && g[x][y] == 0) {
                if (check_connectivity(x, y, tx, ty)) {
                    g[sx][sy] = 0;
                    return true;
                }
            }
        }
        g[sx][sy] = 0;
        return false;
    }

    private boolean draw() {
        for (int i = 0; i < this.rows; i++) {
            for (int j = 0; j < this.cols; j++) {
                g[i][j] = 0;
            }
        }
        for (int r = 0; r < this.rows; r++) {
            g[r][0] = g[r][this.cols - 1] = 1;
        }
        for (int c = 0; c < this.cols; c++) {
            g[0][c] = g[this.rows - 1][c] = 1;
        }
        Random random = new Random();
        for (int i = 0; i < this.inner_walls_count / 2; i++) {
            for (int j = 0; j < 1000; j++) {
                int r = random.nextInt(this.rows);
                int c = random.nextInt(this.cols);
                if (g[r][c] == 1 || g[this.rows - 1 - r][this.cols - 1 - c] == 1) continue;
                if (r == this.rows - 2 && c == 1 || r == 1 && c == this.cols - 2) continue;
                g[r][c] = g[this.rows - 1 - r][this.cols - 1 - c] = 1;
                break;
            }
        }
        return check_connectivity(this.rows - 2, 1, 1, this.cols - 2);
    }

    public void createMap() {
        for (int i = 0; i < 1000; i++) {
            if (draw()) break;
        }
    }
}

这个类主要负责生成带有边界和内部随机墙壁的连通游戏地图，使用了深度优先搜索（DFS）算法来检查地图的连通性。初始化地图大小和墙壁数量，生成并检查连通性，最后提供获取地图的方法供其他模块使用。

小结

整个流程下来，前端通过 WebSocket 保持长连接，后端利用匹配池处理并发请求。JWT 保证了连接的安全性，而 Java 端的算法确保了每次对局地图的随机性和可玩性。这种架构能有效支撑即时对战应用的核心需求。