分布式限流--基于Spring

亦凉 2023-06-11 06:27 24阅读 0赞

## 1 实现方式： ##

自定义注解+拦截器+Redis实现限流 (单体和分布式均适用，全局限流)

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# 下面开始编码 #

## 2 自定义注解： ##

@Inherited
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Limiter { 
       int limit() default 10;
       int sec() default 10;
    }

## 3 拦截器： ##

public class LimitInterceptor implements HandlerInterceptor { 
     @Autowired
     private RedisTemplate<String, Integer> redisTemplate; //使用RedisTemplate操作redis
     @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(Limiter.class)) { 
             return true;
         }
         Limiter limiter = method.getAnnotation(Limiter.class);
         if (limiter == null) { 
             return true;
         }
         int limit = limiter.limit();
         int sec = limiter.sec();
         String key = IPUtil.getIpAddr(request) + request.getRequestURI();
         Integer maxLimit = redisTemplate.opsForValue().get(key);
         if (maxLimit == null) { 
             redisTemplate.opsForValue().set(key, 1, sec, TimeUnit.SECONDS); //set时一定要加过期时间
         } 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 { 
     
     }
     
    }

## 4 controller: ##

@Controller
    @RequestMapping("/study")
    public class limitController { 
        @ResponseBody
        @RequestMapping("/test")
        @Limiter(limit = 10,sec = 100) //加上自定义注解即可
        public String test (HttpServletRequest request,@RequestParam(value = "username",required = false)
         String userName){ 
            //TODO somethings……
            return "hello world !";
        }
    }

## 5 配置文件 ##

/*springmvc的配置文件中加入自定义拦截器*/
    <mvc:interceptors>
     <mvc:interceptor>
     <mvc:mapping path="/**"/>
     <bean class="com.study.controller.limit.LimitInterceptor/>
     </mvc:interceptor>
    </mvc:interceptors>

## 6 测试 ##

使用PostMan工具就可以对我们的接口进行测试。

参考：[https://github.com/crossoverJie/distributed-redis-tool][https_github.com_crossoverJie_distributed-redis-tool]

[https_github.com_crossoverJie_distributed-redis-tool]: https://github.com/crossoverJie/distributed-redis-tool