SpringBoot 自定義注解實現限流
限流是為了防止服務器資源的過度消耗，通過一定的策略來控制訪問頻率，確保服務的高可用性和穩定性。其核心意義在于防止流量高峰時期接口過載，從而引起服務崩潰或響應延遲增加。本文將簡述如何通過AOP和自定義注解實現限流。
1.創建自定義注解
可以根據需要定義更多方法，在方法上引用注解需要指定具體的值
@Target(ElementType.METHOD) //注解的目標是方法上
@Retention(RetentionPolicy.RUNTIME) //運行時
@Documented
public @interface RateLimit {String key() default "";int time() default 1; //時間，單位秒，默認1秒int count() default 100; // 允許的請求次數 ，此處為1秒100次
}2.定義限流切面
使用AOP切面來控制方法的請求次數，如超過注解定義的請求次數限制，將拋出異常
import com.google.common.util.concurrent.RateLimiter;import com.lenovo.ssc.logistics.system.RateLimit;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;@Component
@Aspect
public class RateLimitAspect {private final Map<String ,RateLimiter> limiterMap=new ConcurrentHashMap<>();@Before("@annotation(rateLimit)")public void doBefore(JoinPoint point, RateLimit rateLimit){MethodSignature signature= (MethodSignature)point.getSignature();//獲取方法簽名Method method = signature.getMethod();//獲取當前方法String name = method.getName();//獲取方法名double permitsSecond=(double)rateLimit.count()/ rateLimit.time();//計算每秒允許的請求數//computeIfAbsent 方法會檢查 limiterMap 中是否存在鍵 name。如果鍵 name 不存在，則使用提供的 lambda 表達式 k -> RateLimiter.create(rateLimit.count()) 創建一個新的值，并將其與鍵 name 關聯com.google.common.util.concurrent.RateLimiter rateLimiter = limiterMap.computeIfAbsent(name, k -> com.google.common.util.concurrent.RateLimiter.create(permitsSecond))；if(!rateLimiter.tryAcquire()){//ateLimiter.tryAcquire() 方法用于嘗試從 Guava 的 RateLimiter 限流器中獲取一個許可（token）。如果能夠成功獲取許可，則返回 true，否則返回 falsethrow new RuntimeException("Too many requests");}}}3.使用注解
在Controller中使用@RateLimit注解，time用于指定時間內，count為請求次數
@GetMapping("/queryUsageMap")@Operation(summary = "獲取用途map")@RateLimit(key="queryUsageMap",time = 60,count = 10)public Message<List<Map<String, String>>> queryUsageMap(@RequestParam String language) {List<Map<String, String>> usageList = SealUsageEnum.getUsageList();if (!StringUtils.isEmpty(language)) {if ("en-US".equals(language)) {usageList = SealUsageEnum.getUsageListInEg();}}return new Message<>(ResultCodeEnum.SUCCESS.getCode().toString(), ResultCodeEnum.SUCCESS.getMessage(), usageList);}
4.測試效果
在方法上增加注解，規定時間內，正常訪問；超出頻率報錯如下：
java.lang.RuntimeException: Too many requestsat com.lenovo.ssc.logistics.system.aspect.RateLimitAspect.doBefore(RateLimitAspect.java:36)at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.base/java.lang.reflect.Method.invoke(Method.java:568)at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:634)at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:617)at org.springframework.aop.aspectj.AspectJMethodBeforeAdvice.before(AspectJMethodBeforeAdvice.java:44)at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:57)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:175)at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762)at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762)at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:707)at com.lenovo.ssc.logistics.seal.controller.SealBasicController$$EnhancerBySpringCGLIB$$cfa31bbb.queryUsageMap(<generated>)at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.base/java.lang.reflect.Method.invoke(Method.java:568)at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)at javax.servlet.http.HttpServlet.service(HttpServlet.java:529)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
注意：未使用該注解的方法，將不受限制
以上是使用自定義注解和AOP完成限流的所有內容，更多的限流方式如Bucket4j、Spring Cloud gateway 以及限流組件Sentinel等，關注博主后續。如有不當之處，可以在評論區評論。
