Spring Boot 如何使用 Redis 進(jìn)行 API 防刷限流?

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限流的需求出現(xiàn)在許多常見的場景中：

• 秒殺活動，有人使用軟件惡意刷單搶貨，需要限流防止機(jī)器參與活動

• 某api被各式各樣系統(tǒng)廣泛調(diào)用，嚴(yán)重消耗網(wǎng)絡(luò)、內(nèi)存等資源，需要合理限流

• 淘寶獲取ip所在城市接口、微信公眾號識別微信用戶等開發(fā)接口，免費(fèi)提供給用戶時需要限流，更具有實時性和準(zhǔn)確性的接口需要付費(fèi)。

API 限流實戰(zhàn)

首先我們編寫注解類AccessLimit，使用注解方式在方法上限流更優(yōu)雅更方便！Spring Boot 如何集成 Redis 請點(diǎn)擊這里進(jìn)行閱讀。

三個參數(shù)分別代表有效時間、最大訪問次數(shù)、是否需要登錄，可以理解為 seconds 內(nèi)最多訪問 maxCount 次。

import?java.lang.annotation.ElementType;
import?java.lang.annotation.Retention;
import?java.lang.annotation.RetentionPolicy;
import?java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public?@interface?AccessLimit?{
????int?seconds();
????int?maxCount();
????boolean?needLogin()?default?true;
}

限流的思路：

• 通過路徑:ip的作為key，訪問次數(shù)為value的方式對某一用戶的某一請求進(jìn)行唯一標(biāo)識

• 每次訪問的時候判斷key是否存在，是否count超過了限制的訪問次數(shù)

• 若訪問超出限制，則應(yīng)response返回msg:請求過于頻繁給前端予以展示

import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.stereotype.Component;
import?org.springframework.web.method.HandlerMethod;
import?org.springframework.web.servlet.HandlerInterceptor;

import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;

@Component
public?class?AccessLimtInterceptor?implements?HandlerInterceptor?{

????@Autowired
????private?RedisService?redisService;

????@Override
????public?boolean?preHandle(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler)?throws?Exception?{

????????if?(handler?instanceof?HandlerMethod)?{
????????????HandlerMethod?hm?=?(HandlerMethod)?handler;
????????????AccessLimit?accessLimit?=?hm.getMethodAnnotation(AccessLimit.class);
????????????if?(null?==?accessLimit)?{
????????????????return?true;
????????????}
????????????int?seconds?=?accessLimit.seconds();
????????????int?maxCount?=?accessLimit.maxCount();
????????????boolean?needLogin?=?accessLimit.needLogin();

????????????if?(needLogin)?{
????????????????//判斷是否登錄
????????????}

????????????String?key?=?request.getContextPath()?+?":"?+?request.getServletPath()?+?":"?+?ip?;

????????????Integer?count?=?redisService.get(key);

????????????if?(null?==?count?||?-1?==?count)?{
????????????????redisService.set(key,?1);
????????????????redisService.expire(seconds);
????????????????return?true;
????????????}

????????????if?(count?????????????????redisService.inCr(key);
????????????????return?true;
????????????}

????????????if?(count?>=?maxCount)?{
//????????????????response?返回?json?請求過于頻繁請稍后再試
????????????????return?false;
????????????}
????????}

????????return?true;
????}
}

注冊攔截器并配置攔截路徑和不攔截路徑：

import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.context.annotation.Configuration;
import?org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import?org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

//?extends?WebMvcConfigurerAdapter?已經(jīng)廢棄，java?8開始直接繼承就可以
@Configuration
public?class?IntercepterConfig??implements?WebMvcConfigurer?{
????@Autowired
????private?AccessLimtInterceptor?accessLimtInterceptor;

????@Override
????public?void?addInterceptors(InterceptorRegistry?registry)?{
????????registry.addInterceptor(accessLimtInterceptor)
????????????????.addPathPatterns("/攔截路徑")
????????????????.excludePathPatterns("/不被攔截路徑?通常為登錄注冊或者首頁");
????}
}

在Controller層的方法上直接可以使用注解@AccessLimit

import?org.springframework.web.bind.annotation.GetMapping;
import?org.springframework.web.bind.annotation.RequestMapping;
import?org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("test")
public?class?TestControler?{

????@GetMapping("accessLimit")
????@AccessLimit(seconds?=?3,?maxCount?=?10)
????public?String?testAccessLimit()?{
????????//xxxx
????????return?"";
????}
}

作者：海向

出處：cnblogs.com/haixiang/p/12012728.html

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