本文将介绍在spring项目中自定义注解,借助redis实现接口的限流
自定义注解类
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* 基于注解的请求限制
*/
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface AccessLimit {
/**
* 请求限制数
* @return
*/
int limit();
/**
* 时间范围
* @return
*/
int timeScope();
}
使用注解
我们在需要进行接口防刷的类或者方法上加上该注解即可,
例
/**
* 得到秒杀地址
* 由于秒杀地址较为重要和敏感,为了防止恶意用户刷接口,
* 我们将秒杀接口作为动态的
* @param user
* @param goodsId
* @param tryCode
* @return
*/
@GetMapping("/path")
@ResponseBody
@AccessLimit(limit = 5, timeScope = 5) // 限制5秒内只能请求5次
public Result<String> getMiaoshaPath(HttpServletRequest request, User user, long goodsId, String tryCode) {
// 验证码校验
Boolean verifyPass = kaptchaService.imgVerifyCode(user, goodsId, tryCode);
if (!verifyPass) {
log.info("【执行秒杀】-- 验证码错误");
throw new FlashSaleException(KAPTCHA_VERIFY_FAIL);
}
String path = miaoshaService.createPath(user, goodsId);
return Result.success(path);
};
使用拦截器,在拦截方法时拿到注解上的属性
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
// 从redis中取到值
Cookie cookie = CookieUtil.get(request, Constants.Cookie.TOKEN);
if (cookie == null) {
throw new FlashSaleException(AuthFailEnum.COOKIE_HAVE_NO_TOKEN);
}
StringRedisTemplate redisTemplate = ApplicationContextHolder.get().getBean("stringRedisTemplate", StringRedisTemplate.class);
String userStr = redisTemplate.opsForValue().get(cookie.getValue());
if (StringUtils.isEmpty(userStr)) {
throw new FlashSaleException(AuthFailEnum.REDIS_HAVE_NOT_TOKEN);
}
User user = JSON.parseObject(userStr, User.class);
UserContextHolder.set(user);
if (handler instanceof HandlerMethod) {
HandlerMethod hm = (HandlerMethod) handler;
// 拿到注解的内容
AccessLimit accessLimit = hm.getMethodAnnotation(AccessLimit.class);
if (accessLimit == null) {
// 不需要限流验证
return true;
} else {
// 需要限流验证
int limit = accessLimit.limit();
int timeScope = accessLimit.timeScope();
// 次数校验(借助redis实现基于用户的限流验证)
String requestURI = request.getRequestURI();
final String redisKey = Constants.Cache.PATH_COUNT_PREFIX + user.getId() + ":" + requestURI;
String currentCount = redisTemplate.opsForValue().get(redisKey);
if (!StringUtils.isEmpty(currentCount)) {
int count = Integer.valueOf(currentCount);
if (count < limit) {
redisTemplate.opsForValue().increment(redisKey, 1);
} else {
// 访问过于频繁
throw new FlashSaleException(PATH_LIMIT_REACHED);
}
} else {
redisTemplate.opsForValue().set(redisKey, "1", timeScope, TimeUnit.SECONDS);
}
}
}
UserContextHolder.set(user);
renewExpiretime(response, cookie, userStr);
return true;
}
总结
在实现了上述代码后,当我们访问到带有AccessLimit注解的方法或类时,只要拦截器拦截了该请求,就能通过getMethodAnnotation()拿到注解上的limit和timeScope属性,然后借助redis实现限流;比如某些接口我们可能想要2秒只能访问1次,那么就把limit=1 timeScope=2,某些接口我们想要限制1分钟访问10次,就把limit=10, timeScope=60