Implementing a Custom AccessLimit Annotation and Interceptor for Rate Limiting in Spring Boot

The author, a Java architect, introduces a practical tutorial on building a custom rate‑limiting mechanism for Spring Boot applications using a user‑defined annotation and an interceptor.

Step 1 – Define the annotation:

import java.lang.annotation.Retention;<br/>import java.lang.annotation.Target;<br/><br/>import static java.lang.annotation.ElementType.METHOD;<br/>import static java.lang.annotation.RetentionPolicy.RUNTIME;<br/><br/>@Retention(RUNTIME)<br/>@Target(METHOD)<br/>public @interface AccessLimit {<br/>    int seconds();<br/>    int maxCount();<br/>    boolean needLogin() default true;<br/>}

Step 2 – Implement the interceptor that reads the annotation, checks login status, and uses Redis to count requests:

import com.alibaba.fastjson.JSON;<br/>import com.example.demo.action.AccessLimit;<br/>import com.example.demo.redis.RedisService;<br/>import com.example.demo.result.CodeMsg;<br/>import com.example.demo.result.Result;<br/>import org.springframework.beans.factory.annotation.Autowired;<br/>import org.springframework.stereotype.Component;<br/>import org.springframework.web.method.HandlerMethod;<br/>import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;<br/><br/>import javax.servlet.http.HttpServletRequest;<br/>import javax.servlet.http.HttpServletResponse;<br/>import java.io.OutputStream;<br/><br/>@Component<br/>public class FangshuaInterceptor extends HandlerInterceptorAdapter {<br/><br/>    @Autowired<br/>    private RedisService redisService;<br/><br/>    @Override<br/>    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {<br/>        if (handler instanceof HandlerMethod) {<br/>            HandlerMethod hm = (HandlerMethod) handler;<br/>            AccessLimit accessLimit = hm.getMethodAnnotation(AccessLimit.class);<br/>            if (accessLimit == null) {<br/>                return true;<br/>            }<br/>            int seconds = accessLimit.seconds();<br/>            int maxCount = accessLimit.maxCount();<br/>            boolean login = accessLimit.needLogin();<br/>            String key = request.getRequestURI();<br/>            if (login) {<br/>                // In a real project, obtain the user ID from the session<br/>                key += "" + "1"; // placeholder user ID<br/>            }<br/>            AccessKey ak = AccessKey.withExpire(seconds);<br/>            Integer count = redisService.get(ak, key, Integer.class);<br/>            if (count == null) {<br/>                redisService.set(ak, key, 1);<br/>            } else if (count < maxCount) {<br/>                redisService.incr(ak, key);<br/>            } else {<br/>                render(response, CodeMsg.ACCESS_LIMIT_REACHED);<br/>                return false;<br/>            }<br/>        }<br/>        return true;<br/>    }<br/><br/>    private void render(HttpServletResponse response, CodeMsg cm) throws Exception {<br/>        response.setContentType("application/json;charset=UTF-8");<br/>        OutputStream out = response.getOutputStream();<br/>        String str = JSON.toJSONString(Result.error(cm));<br/>        out.write(str.getBytes("UTF-8"));<br/>        out.flush();<br/>        out.close();<br/>    }<br/>}

Step 3 – Register the interceptor in Spring Boot configuration:

import com.example.demo.ExceptionHander.FangshuaInterceptor;<br/>import org.springframework.beans.factory.annotation.Autowired;<br/>import org.springframework.context.annotation.Configuration;<br/>import org.springframework.web.servlet.config.annotation.InterceptorRegistry;<br/>import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;<br/><br/>@Configuration<br/>public class WebConfig extends WebMvcConfigurerAdapter {<br/><br/>    @Autowired<br/>    private FangshuaInterceptor interceptor;<br/><br/>    @Override<br/>    public void addInterceptors(InterceptorRegistry registry) {<br/>        registry.addInterceptor(interceptor);<br/>    }<br/>}

Step 4 – Apply the annotation to a controller method to enforce the limit:

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

The article concludes with a brief invitation to share the tutorial and join a community of architects for further learning.