Implementing IP+URL Rate Limiting with Spring Boot Interceptor and Redis Distributed Lock

In a Spring Boot project, the article demonstrates how to protect services from malicious requests by limiting the number of accesses to a specific URL from the same IP within a given time window.

The solution uses a custom HandlerInterceptor that records request counts in Redis and disables the IP when the limit is exceeded, returning a JSON error response.

The core interceptor code is:

@Slf4j
public class IpUrlLimitInterceptor implements HandlerInterceptor {
    private RedisUtil getRedisUtil() {
        return SpringContextUtil.getBean(RedisUtil.class);
    }
    private static final String LOCK_IP_URL_KEY = "lock_ip_";
    private static final String IP_URL_REQ_TIME = "ip_url_times_";
    private static final long LIMIT_TIMES = 5;
    private static final int IP_LOCK_TIME = 60;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("request请求地址uri={},ip={}", request.getRequestURI(), IpAdrressUtil.getIpAdrress(request));
        if (ipIsLock(IpAdrressUtil.getIpAdrress(request))) {
            log.info("ip访问被禁止={}", IpAdrressUtil.getIpAdrress(request));
            ApiResult result = new ApiResult(ResultEnum.LOCK_IP);
            returnJson(response, JSON.toJSONString(result));
            return false;
        }
        if (!addRequestTime(IpAdrressUtil.getIpAdrress(request), request.getRequestURI())) {
            ApiResult result = new ApiResult(ResultEnum.LOCK_IP);
            returnJson(response, JSON.toJSONString(result));
            return false;
        }
        return true;
    }

    @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 { }

    private Boolean ipIsLock(String ip) {
        RedisUtil redisUtil = getRedisUtil();
        if (redisUtil.hasKey(LOCK_IP_URL_KEY + ip)) {
            return true;
        }
        return false;
    }

    private Boolean addRequestTime(String ip, String uri) {
        String key = IP_URL_REQ_TIME + ip + uri;
        RedisUtil redisUtil = getRedisUtil();
        if (redisUtil.hasKey(key)) {
            long time = redisUtil.incr(key, 1L);
            if (time >= LIMIT_TIMES) {
                redisUtil.getLock(LOCK_IP_URL_KEY + ip, ip, IP_LOCK_TIME);
                return false;
            }
        } else {
            redisUtil.getLock(key, 1L, 1);
        }
        return true;
    }

    private void returnJson(HttpServletResponse response, String json) throws Exception {
        PrintWriter writer = null;
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/json; charset=utf-8");
        try {
            writer = response.getWriter();
            writer.print(json);
        } catch (IOException e) {
            log.error("LoginInterceptor response error ---> {}", e.getMessage(), e);
        } finally {
            if (writer != null) {
                writer.close();
            }
        }
    }
}

RedisUtil provides distributed‑lock utilities used by the interceptor:

@Component
@Slf4j
public class RedisUtil {
    private static final Long SUCCESS = 1L;

    @Autowired
    private RedisTemplate<String, Object> redisTemplate;

    public boolean getLock(String lockKey, Object value, int expireTime) {
        try {
            log.info("添加分布式锁key={},expireTime={}", lockKey, expireTime);
            String script = "if redis.call('setNx',KEYS[1],ARGV[1]) then if redis.call('get',KEYS[1])==ARGV[1] then return redis.call('expire',KEYS[1],ARGV[2]) else return 0 end end";
            RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);
            Object result = redisTemplate.execute(redisScript, Collections.singletonList(lockKey), value, expireTime);
            if (SUCCESS.equals(result)) {
                return true;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }

    public boolean releaseLock(String lockKey, String value) {
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);
        Object result = redisTemplate.execute(redisScript, Collections.singletonList(lockKey), value);
        if (SUCCESS.equals(result)) {
            return true;
        }
        return false;
    }
}

Finally, the interceptor is registered in a configuration class:

@Configuration
@Slf4j
public class MyWebAppConfig extends WebMvcConfigurerAdapter {
    @Bean
    IpUrlLimitInterceptor getIpUrlLimitInterceptor() {
        return new IpUrlLimitInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(getIpUrlLimitInterceptor()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
}