SpringMVC 限流

在使用SpringBoot做接口访问如何做接口的限流，这里我们可以使用google的Guava包来实现，当然我们也可以自己实现限流，Guava中的限流是久经考验的我们没必需重新再去写一个，如果想了解限流原理的同学可以自己查阅一下相关的资料，本文不作过来说明噢。

在项目中引入Guava相关包

http://mvnrepository.com/artifact/com.google.guava/guava/21.0

maven项目

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>21.0</version>
</dependency>

gradle项目

compile group: 'com.google.guava', name: 'guava', version: '21.0'

写一个SpringMVC的拦截器
SmoothBurstyInterceptor.java

import com.google.common.util.concurrent.RateLimiter;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.concurrent.TimeUnit;

public class SmoothBurstyInterceptor extends HandlerInterceptorAdapter {

    public enum LimitType {
        DROP,//丢弃
        WAIT //等待
    }

    /**
     * 限流器
     */
    private RateLimiter limiter;
    /**
     * 限流方式
     */
    private LimitType limitType = LimitType.DROP;

    public SmoothBurstyInterceptor() {
        this.limiter = RateLimiter.create(10);
    }

    /**
     * @param tps       限流量 (每秒处理量)
     * @param limitType 限流类型:等待/丢弃(达到限流量)
     */
    public SmoothBurstyInterceptor(int tps, SmoothBurstyInterceptor.LimitType limitType) {
        this.limiter = RateLimiter.create(tps);
        this.limitType = limitType;
    }
    /**
     * @param permitsPerSecond  每秒新增的令牌数
     * @param limitType 限流类型:等待/丢弃(达到限流量)
     */
    public SmoothBurstyInterceptor(double permitsPerSecond, SmoothBurstyInterceptor.LimitType limitType) {
        this.limiter = RateLimiter.create(permitsPerSecond, 1000, TimeUnit.MILLISECONDS);
        this.limitType = limitType;
    }

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (limitType.equals(LimitType.DROP)) {
            if (limiter.tryAcquire()) {
                return super.preHandle(request, response, handler);
            }
        } else {
            limiter.acquire();
            return super.preHandle(request, response, handler);
        }
        throw new Exception("网络异常!");//达到限流后，往页面提示的错误信息。
    }

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

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

    public RateLimiter getLimiter() {
        return limiter;
    }

    public void setLimiter(RateLimiter limiter) {
        this.limiter = limiter;
    }
}

SpringMVC拦截配置
WebConfig.java

@Component
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 多个拦截器组成一个拦截器链
        registry.addInterceptor(new SmoothBurstyInterceptor(100, SmoothBurstyInterceptor.LimitType.DROP)).addPathPatterns("/**");
        //限流可配置为SmoothBurstyInterceptor.LimitType.DROP丢弃请求或者SmoothBurstyInterceptor.LimitType.WAIT等待，100为每秒的速率
        super.addInterceptors(registry);
    }

}