How to Implement Redis Cache Preheating in Spring

Cache Preheating

Cache preheating loads hot data into a cache (e.g., Redis) during application startup or after cache expiration, so subsequent requests find the data already cached, reducing cache penetration, cache breakdown, and load on the database.

Abstract Cache Class

public abstract class AbstractCache {
    /** Initialize cache */
    protected abstract void init();

    /** Retrieve cached value */
    public abstract <T> T get();

    /** Clear cache */
    public abstract void clear();

    /** Reload cache */
    public void reload() {
        clear();
        init();
    }
}

Spring ApplicationContext Utility

@Component
public class ApplicationContextUtil implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext ctx) throws BeansException {
        ApplicationContextUtil.applicationContext = ctx;
    }

    /** Obtain the Spring context */
    public static ApplicationContext getContext() {
        return applicationContext;
    }
}

Cache Preheat Handler (CommandLineRunner)

@Component
@ConditionalOnProperty(name = {"cache.init.enable"}, havingValue = "true", matchIfMissing = false)
public class CachePreheatHandler implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        ApplicationContext ctx = ApplicationContextUtil.getContext();
        java.util.Map<String, AbstractCache> beans = ctx.getBeansOfType(AbstractCache.class);
        for (java.util.Map.Entry<String, AbstractCache> entry : beans.entrySet()) {
            AbstractCache cache = ctx.getBean(entry.getValue().getClass());
            cache.init();
        }
    }
}

The handler executes only when the configuration property cache.init.enable is set to true (default false).

cache.init.enable=true

Example: News Cache

@Component
@RequiredArgsConstructor
public class NewsCache extends AbstractCache {
    private static final String NEWS_KEY = "news";
    private final RedisTemplate<String, Object> redisTemplate;
    private final NewsService newsService;

    @Override
    protected void init() {
        if (Boolean.FALSE.equals(redisTemplate.hasKey(NEWS_KEY))) {
            redisTemplate.opsForValue().set(NEWS_KEY, newsService.list(), 30, TimeUnit.MINUTES);
        }
    }

    @Override
    public <T> T get() {
        if (Boolean.FALSE.equals(redisTemplate.hasKey(NEWS_KEY))) {
            reload();
        }
        return (T) redisTemplate.opsForValue().get(NEWS_KEY);
    }

    @Override
    public void clear() {
        redisTemplate.delete(NEWS_KEY);
    }
}

When the application starts, NewsCache.init() stores the hot news list in Redis under the key news with a 30‑minute TTL.

Controller Accessing the Cache

@RestController
@RequestMapping("/news")
@RequiredArgsConstructor
public class NewsController {
    private final NewsCache newsCache;

    @GetMapping("/cache")
    public java.util.List<News> list() {
        return newsCache.get();
    }
}

After startup, a request to /news/cache returns the pre‑loaded news data directly from Redis without triggering a database query.