Java如何实现接口限流

小编给大家分享一下Java如何实现接口限流，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

RateLimiter

Google开源工具包Guava提供了限流工具类RateLimiter，基于令牌桶算法实现。

1.maven依赖：

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>27.1-jre</version>
</dependency>

2.自定义注解

import java.lang.annotation.*;
import java.util.concurrent.TimeUnit;

/**
 * 令牌桶注解实现
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestLimiter {
    /**
     * 每秒创建令牌个数，默认:10
     */
    double QPS() default 10D;

    /**
     * 获取令牌等待超时时间 默认:500
     */
    long timeout() default 500;

    /**
     * 超时时间单位 默认:毫秒
     */
    TimeUnit timeunit() default TimeUnit.MILLISECONDS;

    /**
     * 无法获取令牌返回提示信息
     */
    String msg() default "请稍后再试!";
}

3.拦截器

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.google.common.util.concurrent.RateLimiter;
import com.tiam.panshi.cloud.appback.annotation.RequestLimiter;
import lombok.extern.slf4j.Slf4j;
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;
import java.io.PrintWriter;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

@Component
@Slf4j
public class RequestLimitingInterceptor implements HandlerInterceptor {
    private final Map<String, RateLimiter> rateLimiterMap = new ConcurrentHashMap<>();

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        //这里可以抽出去定义返回信息
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("10001", "玩命加载中,请稍后再试");
        try {
            if (handler instanceof HandlerMethod) {
                HandlerMethod handlerMethod = (HandlerMethod) handler;
                RequestLimiter rateLimit = handlerMethod.getMethodAnnotation(RequestLimiter.class);
                //判断是否有注解
                if (rateLimit != null) {
                    // 获取请求url
                    String url = request.getRequestURI();
                    RateLimiter rateLimiter;
                    // 判断map集合中是否有创建好的令牌桶
                    if (!rateLimiterMap.containsKey(url)) {
                        // 创建令牌桶,以n r/s往桶中放入令牌
                        rateLimiter = RateLimiter.create(rateLimit.QPS());
                        rateLimiterMap.put(url, rateLimiter);
                    }
                    rateLimiter = rateLimiterMap.get(url);
                    // 获取令牌
                    boolean acquire = rateLimiter.tryAcquire(rateLimit.timeout(), rateLimit.timeunit());
                    if (acquire) {
                        //获取令牌成功
                        return true;
                    } else {
                        log.warn("请求被限流,url:{}", request.getServletPath());
                        makeResult(response, renderJson(jsonObject));
                        return false;
                    }
                }
            }
            return true;
        } catch (Exception var6) {
            var6.printStackTrace();
            makeResult(response, renderJson(jsonObject));
            return false;
        }
    }

    private void makeResult(HttpServletResponse response, JSONObject jo) {
        response.setContentType("application/json; charset=utf-8");
        response.setCharacterEncoding("UTF-8");
        try (PrintWriter out = response.getWriter()) {
            out.append(jo.toJSONString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private JSONObject renderJson(Object o) {
        return JSONObject.parseObject(JSON.toJSONString(o));
    }

4.注册拦截器

@Configuration
public class WebMvcConfig extends WebMvcConfigurationSupport {

     /**
      * 请求限流拦截器
      */
     @Autowired
     protected RequestLimitingInterceptor requestLimitingInterceptor;

     @Override
     public void addInterceptors(InterceptorRegistry registry) {
         // 请求限流
         registry.addInterceptor(requestLimitingInterceptor).addPathPatterns("/**");
     }

}

5.在接口上配置注解

@RequestLimiter(QPS = 5D, timeout = 200, timeunit = TimeUnit.MILLISECONDS,msg = "玩命加载中,请稍后再试")
@GetMapping("/test")
@ResponseBody
public String test(){
      return "";
}

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