TreadLocal同一线程数据共享

使用案例（在购物车页面获取登录用户信息）

使用拦截器

/**
 *在执行目标方法之前，判断用户的登录状态。并封装传递给controller目标请求
 *
 **/
@Component
public class CartInterceptor implements HandlerInterceptor {

   public static ThreadLocal<UserInfoTo> threadLocal = new ThreadLocal<>();

   @Override
   public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
         throws Exception {
      UserInfoTo userInfoTo = new UserInfoTo();
      //正常用户信息存放至session
      HttpSession session = request.getSession();
      MemberRespVo member = (MemberRespVo) session.getAttribute(AuthServerConstant.LOGIN_USER);
      if (member !=null){
         //用户登录
         userInfoTo.setUserId(member.getId());
      }
      Cookie[] cookies = request.getCookies();
      //临时用户信息存放至cookie
      if (cookies!=null && cookies.length>0){
         for (Cookie cookie : cookies) {
            //user-key
            String name = cookie.getName();
            if (name.equals(CartConstant.TMP_USER_COOKIE_NAME)){
               userInfoTo.setUserKey(cookie.getValue());
               userInfoTo.setTempUser(true);
            }
         }
         //如果没有临时用户,创建一个user-key
         if (!StringUtils.isEmpty(userInfoTo.getUserKey())){
            String uuid = UUID.randomUUID().toString().replace("-","");
            userInfoTo.setUserKey(uuid);
         }
      }
      //目标方法执行之前
      threadLocal.set(userInfoTo);
      return true;
   }

   /**
    * 业务执行之后,分配临时用户，让浏览器保存
    */
   @Override
   public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {

      UserInfoTo userInfoTo = threadLocal.get();

      if (!userInfoTo.isTempUser()){
         Cookie cookie = new Cookie(CartConstant.TMP_USER_COOKIE_NAME, userInfoTo.getUserKey());
         cookie.setDomain("gulimall.com");
         cookie.setMaxAge(CartConstant.TMP_USER_COOKIE_TIMEOUT);
         response.addCookie(cookie);
      }
   }
}

 要使拦截器生效还需配置WebMvcConfigurer

public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry){
        registry.addInterceptor(new CartInterceptor()).addPathPatterns("/**");
    }
}

在需要用到地方使用拦截器组件.出threadLocal

    private BoundHashOperations<String, Object, Object> getCartOps() {
        UserInfoTo userInfoTo = CartInterceptor.threadLocal.get();
        String cartKey = "";
        if (userInfoTo.getUserId() != null) {
            //gulimall:cart:1
            cartKey    = CART_PREFIX + userInfoTo.getUserId();
        }    else {
            cartKey = CART_PREFIX + userInfoTo.getUserKey();
        }
        BoundHashOperations<String, Object, Object> operations = redisTemplate.boundHashOps(cartKey);

        return operations;
    }