springboot工程中限流方式

限流，是防止用户恶意刷新接口。常见的限流方式有阿里开源的sentinel、redis等。
1、google的guava，令牌桶算法实现限流
Guava的 RateLimiter提供了令牌桶算法实现：平滑突发限流(SmoothBursty)和平滑预热限流(SmoothWarmingUp)实现。

// RateLimiter提供了两个工厂方法，最终会调用下面两个函数，生成RateLimiter的两个子类。
static RateLimiter create(SleepingStopwatch stopwatch, double permitsPerSecond) {
 	RateLimiter rateLimiter = new SmoothBursty(stopwatch, 1.0 /* maxBurstSeconds */);
    rateLimiter.setRate(permitsPerSecond);
 	return rateLimiter;
}
static RateLimiter create(
 	SleepingStopwatch stopwatch, double permitsPerSecond, long warmupPeriod, TimeUnit unit,
 double coldFactor) {
 	RateLimiter rateLimiter = new SmoothWarmingUp(stopwatch, warmupPeriod, unit, coldFactor);
    rateLimiter.setRate(permitsPerSecond);
 	return rateLimiter;
}
    

平滑突发限流：使用 RateLimiter的静态方法创建一个限流器，设置每秒放置的令牌数为10个。返回的RateLimiter对象可以保证1秒内不会给超过10个令牌，并且以固定速率进行放置，达到平滑输出的效果。
平滑预热限流：RateLimiter的 SmoothWarmingUp是带有预热期的平滑限流，它启动后会有一段预热期，逐步将分发频率提升到配置的速率。

@RestController
public class HomeController {

    // 这里的10表示每秒允许处理的量为10个
    private RateLimiter limiter = RateLimiter.create(10);
    private RateLimiter limiter2 = RateLimiter.create(2, 1000, TimeUnit.SECONDS);
    //permitsPerSecond: 表示 每秒新增 的令牌数;warmupPeriod: 表示在从 冷启动速率 过渡到 平均速率 的时间间隔

    @GetMapping("/test/{name}")
    public String test(@PathVariable("name") String name) {
        // 请求RateLimiter, 超过permits会被阻塞
        final double acquire = limiter.acquire();
        System.out.println("acquire=" + acquire);
        //判断double是否为空或者为0
        if (acquire == 0) {
            return name;
        } else {
            return "操作太频繁";
        }
    }

    @AccessLimit(limit = 2, sec = 10)
    @GetMapping("/test2/{name}")
    public String test2(@PathVariable("name") String name) {
        return name;
    }
}

2、interceptor+redis根据注解限流

public class AccessLimitInterceptor implements HandlerInterceptor {

    @Resource
    private RedisTemplate redisTemplate;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            Method method = handlerMethod.getMethod();
            if (!method.isAnnotationPresent(AccessLimit.class)) {
                return true;
            }
            AccessLimit accessLimit = method.getAnnotation(AccessLimit.class);
            if (accessLimit == null) {
                return true;
            }
            int limit = accessLimit.limit();
            int sec = accessLimit.sec();
            String key = IPUtil.getIpAddress(request) + request.getRequestURI();
            //资源唯一标识
            Integer maxLimit = redisTemplate.opsForValue().get(key);
            if (maxLimit == null) {
                //set时一定要加过期时间
                redisTemplate.opsForValue().set(key, 1, sec, TimeUnit.SECONDS);
            } else if (maxLimit < limit) {
                redisTemplate.opsForValue().set(key, maxLimit + 1, sec, TimeUnit.SECONDS);
            } else {
                output(response, "请求太频繁!");
                return false;
            }
        }
        return true;
    }

    public void output(HttpServletResponse response, String msg) throws IOException {
        response.setContentType("application/json;charset=UTF-8");
        ServletOutputStream outputStream = null;
        try {
            outputStream = response.getOutputStream();
            outputStream.write(msg.getBytes("UTF-8"));
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            outputStream.flush();
            outputStream.close();
        }
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

@Configuration
public class InterceptorConfig extends WebMvcConfigurationSupport {

    @Bean
    public AccessLimitInterceptor accessLimitInterceptor() {
        return new AccessLimitInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //addPathPatterns 添加拦截规则
        registry.addInterceptor(accessLimitInterceptor()).addPathPatterns("/**");
    }

    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/");
    }
}

@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate template = new RedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        template.setKeySerializer(new StringRedisSerializer());
        template.setValueSerializer(new GenericJackson2JsonRedisSerializer());
        template.setHashKeySerializer(new GenericJackson2JsonRedisSerializer());
        template.setHashValueSerializer(new GenericJackson2JsonRedisSerializer());
        template.afterPropertiesSet();
        return template;
    }
}

限流方式还有很多，后续继续尝试。