1、防刷限流实现1

1、本章诉求

限流的需求出现在许多常见的场景中：

秒杀活动，有人使用软件恶意刷单抢货，需要限流防止机器参与活动
某api被各式各样系统广泛调用，严重消耗网络、内存等资源，需要合理限流

2、流程设计

在这里插入图片描述

3、方案实现

3.1、实现思路：

通过ip:api路径的作为key，访问次数为value的方式对某一用户的某一请求进行唯一标识
每次访问的时候判断key是否存在，是否count超过了限制的访问次数
若访问超出限制，则应response返回msg:请求过于频繁给前端予以展示

3.2、编码实现

技术要点：redis、自定义注解、拦截器

application.yml

server:
  port: 8080

spring:
  redis:
    database: 0
    host: 127.0.0.1
    port: 6379
    timeout: 30000ms
    lettuce:
      pool:
        max-active: 8
        max-idle: 8
        max-wait: 500ms
        min-idle: 0

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>coderhome-access-limit</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- spring data redis -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

        <!-- spring2.X集成redis所需common-pool2-->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.6.0</version>
        </dependency>
    </dependencies>

</project>

启动类WebApplication

package club.coderhome;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class WebApplication {

    public static void main(String[] args) {
        SpringApplication.run(WebApplication.class, args);
    }

}

RedisConfig

package club.coderhome.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

/**
 * @Author 北冥有鱼
 * @Description redis配置类
 * @Date 2023/5/5 20:15
 */
@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory connectionFactory) {
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(connectionFactory);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new Jackson2JsonRedisSerializer(Object.class));
        return redisTemplate;
    }
    @Bean
    public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory connectionFactory) {
        StringRedisTemplate redisTemplate = new StringRedisTemplate();
        redisTemplate.setConnectionFactory(connectionFactory);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new StringRedisSerializer());
        return redisTemplate;
    }
}

编写自定义注解类CurrentLimit

/**
 * @Author 北冥有鱼
 * @Description 限流注解:三个参数分别代表有效时间、最大访问次数、是否需要登录，可以理解为 expirationTime 内最多访问 maxCount 次。
 * @Date 2023/5/5 20:42
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CurrentLimit {

    //有效时间,单位ms,默认10000ms
    int expirationTime() default 10000;

    //最大访问次数
    int maxCount();

    //是否需要登录
    boolean needLogin() default true;
}

拦截器CurrentLimtInterceptor

/**
 * @Author 北冥有鱼
 * @Description 自定义限流拦截器
 * @Date 2023/5/5 20:47
 */
@Component
public class CurrentLimtInterceptor implements HandlerInterceptor {

    @Resource
    private RedisTemplate redisTemplate;

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

        if (handler instanceof HandlerMethod) {
            HandlerMethod hm = (HandlerMethod) handler;
            //获取注解信息
            CurrentLimit accessLimit = hm.getMethodAnnotation(CurrentLimit.class);
            if (null == accessLimit) {
                return true;
            }
            int expirationTime = accessLimit.expirationTime();
            int maxCount = accessLimit.maxCount();
            boolean needLogin = accessLimit.needLogin();

            if (needLogin) {
                //判断是否登录
            }

            //客户端ip地址
            String ip = request.getRemoteAddr();
            String key = ip + ":" + request.getServletPath();

            Integer count = (Integer) redisTemplate.opsForValue().get(key);
            //第一次访问
            if (null == count || -1 == count) {
                //设置值，并设置过期时间
                redisTemplate.opsForValue().set(key, 1, expirationTime, TimeUnit.MILLISECONDS);
                return true;
            }

            //如果访问次数<最大次数，则加1操作
            if (count < maxCount) {
                redisTemplate.opsForValue().increment(key, 1);
                return true;
            }

            //超过最大值返回操作频繁
            if (count >= maxCount) {
                System.out.println("count==" + count);
                //解决乱码问题
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("请求过于频繁，请稍后再试");
                return false;
            }
        }
        return true;
    }
}

注册拦截器并配置拦截规则

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {

    @Autowired
    private CurrentLimtInterceptor currentLimtInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(currentLimtInterceptor)
                .addPathPatterns("/draw/**")//拦截器拦截的请求路径
                .excludePathPatterns("/access/login");
    }
}

在Controller层的方法上直接可以使用注解@AccessLimit

@RestController
@RequestMapping("/draw")
public class DrawController {

    @ResponseBody
    @GetMapping("/doDraw")
    @CurrentLimit(expirationTime = 30000, maxCount = 3)
    public String accessLimit() {
        return "恭喜你，抽中iphone25一台";
    }
}