static class Entry extends WeakReference<ThreadLocal<?>> {
        /** The value associated with this ThreadLocal. */
        Object value;
        Entry(ThreadLocal<?> k, Object v) {
            super(k);
            value = v;
        }
    }
}

@Component
public class HostHolder {
    private ThreadLocal<User> users = new ThreadLocal<>();
    public User getUser() {
        return users.get();
    }
    public void setUser(User user) {
        users.set(user);
    }
    public void clear() {
        users.remove();
    }
}

/**
 * 登錄攔截器
 */
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 在請求處理之前進行調(diào)用，返回true則繼續(xù)向下執(zhí)行，返回false則中斷請求
        String loginId = request.getHeader("loginId");
        if (StringUtils.isNotBlank(loginId)) {
            // 如果請求頭中包含loginId，將其設置到LoginContextHolder中
            LoginContextHolder.set("loginId", loginId);
        }
        return true;
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        // 在整個請求結束之后被調(diào)用，也就是在DispatcherServlet渲染了對應的視圖之后執(zhí)行，主要是做清理工作
        // 移除LoginContextHolder中的loginId
        LoginContextHolder.remove();
    }
}