Implementing Interface Rate Limiting in Spring Boot with Annotations and Redis

The article explains a practical way to add rate‑limiting to Spring Boot APIs by using a custom annotation and Redis.

Technical points: basic Spring Boot knowledge, Redis basic operations

First, define an annotation class:

import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
 * @author yhq
 * @date 2018/9/10 15:52
 */
@Retention(RUNTIME)
@Target(METHOD)
public @interface AccessLimit {
    int seconds();
    int maxCount();
    boolean needLogin() default true;
}

Next, implement the interceptor that checks the annotation, retrieves the request count from Redis, and decides whether to allow the request:

import com.alibaba.fastjson.JSON;
import com.example.demo.action.AccessLimit;
import com.example.demo.redis.RedisService;
import com.example.demo.result.CodeMsg;
import com.example.demo.result.Result;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.OutputStream;
/**
 * @author yhq
 * @date 2018/9/10 16:05
 */
@Component
public class FangshuaInterceptor extends HandlerInterceptorAdapter {
    @Autowired
    private RedisService redisService;
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (handler instanceof HandlerMethod) {
            HandlerMethod hm = (HandlerMethod) handler;
            AccessLimit accessLimit = hm.getMethodAnnotation(AccessLimit.class);
            if (accessLimit == null) {
                return true;
            }
            int seconds = accessLimit.seconds();
            int maxCount = accessLimit.maxCount();
            boolean login = accessLimit.needLogin();
            String key = request.getRequestURI();
            if (login) {
                // Assume user id is 1 for demonstration; replace with actual user id retrieval
                key += "" + "1";
            }
            AccessKey ak = AccessKey.withExpire(seconds);
            Integer count = redisService.get(ak, key, Integer.class);
            if (count == null) {
                // first access
                redisService.set(ak, key, 1);
            } else if (count < maxCount) {
                // increment count
                redisService.incr(ak, key);
            } else {
                // exceed limit
                render(response, CodeMsg.ACCESS_LIMIT_REACHED);
                return false;
            }
        }
        return true;
    }
    private void render(HttpServletResponse response, CodeMsg cm) throws Exception {
        response.setContentType("application/json;charset=UTF-8");
        OutputStream out = response.getOutputStream();
        String str = JSON.toJSONString(Result.error(cm));
        out.write(str.getBytes("UTF-8"));
        out.flush();
        out.close();
    }
}

Register the interceptor in a Spring Boot configuration class:

import com.example.demo.ExceptionHander.FangshuaInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
/**
 * @author yhq
 * @date 2018/9/10 15:58
 */
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Autowired
    private FangshuaInterceptor interceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(interceptor);
    }
}

Finally, apply the @AccessLimit annotation to a controller method to protect the endpoint:

import com.example.demo.result.Result;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
/**
 * @author yhq
 * @date 2018/9/10 15:49
 */
@Controller
public class FangshuaController {
    @AccessLimit(seconds = 5, maxCount = 5, needLogin = true)
    @RequestMapping("/fangshua")
    @ResponseBody
    public Result<String> fangshua() {
        return Result.success("请求成功");
    }
}

The complete example shows how to combine a custom annotation, Redis caching, and a Spring MVC interceptor to achieve simple, configurable rate limiting for API interfaces.