基于SpringBoot+WebSocket实现网页在线聊天室

浏览器页面
  ├── login.html    登录页
  ├── register.html 注册页
  └── client.html   聊天主界面
↓ HTTP / WebSocket
Spring Boot 后端
  ├── Controller    接口层（用户/好友/消息/会话）
  ├── Interceptor   登录拦截器
  ├── Exception     全局异常处理
  ├── WebSocket     实时消息推送
  └── MyBatis       数据持久层
↓ MySQL
用户表、好友表、会话表、消息表、会话用户关联表

@PostMapping("/login")
public Object login(String username, String password, HttpServletRequest req) {
    User user = userMapper.selectByName(username);
    if(user == null || !user.getPassword().equals(password)) {
        return new User();
    }
    HttpSession session = req.getSession(true);
    session.setAttribute("user", user);
    return user;
}

@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
    HttpSession session = request.getSession(false);
    if (session == null || session.getAttribute("user") == null) {
        response.setContentType("application/json;charset=utf-8");
        response.setStatus(401);
        response.getWriter().write("请先登录");
        return false;
    }
    return true;
}

// 在线用户管理（线程安全）
private ConcurrentHashMap<Integer, WebSocketSession> sessions = new ConcurrentHashMap<>();
public void online(int userId, WebSocketSession session) {
    sessions.put(userId, session);
}
public WebSocketSession getSession(int userId) {
    return sessions.get(userId);
}

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(NoResourceFoundException.class)
    public Result handleNoResource() {
        return Result.success(null);
    }
    @ExceptionHandler(Exception.class)
    public Result handleError(Exception e) {
        return Result.fail("服务器异常");
    }
}