How to use BlockingCache from Ehcache in Spring?

Question

I want to implement a blocking cache for multiple requests at some time.

Currently I have this:

In file AppConfig.java I defined the cache manager

@EnableCaching
@Configuration
public class AppConfig implements WebMvcConfigurer {

    @Bean
    public CacheManager cacheManager() {
        return new EhCacheCacheManager(Objects.requireNonNull(ehCacheCacheManager().getObject()));
    }

    @Bean
    public EhCacheManagerFactoryBean ehCacheCacheManager() {
        EhCacheManagerFactoryBean cacheManagerFactoryBean = new EhCacheManagerFactoryBean();
        cacheManagerFactoryBean.setConfigLocation(new ClassPathResource("ehcache.xml"));
        cacheManagerFactoryBean.setShared(true);
        return cacheManagerFactoryBean;
    }
}

Here is BlockingCache definition from file: BlockingCacheDecoratorFactory.java

@Component
public class BlockingCacheDecoratorFactory extends CacheDecoratorFactory {

    public Ehcache createDecoratedEhcache(final Ehcache cache, final Properties properties) {
        return new BlockingCache(cache);
    }

    public Ehcache createDefaultDecoratedEhcache(final Ehcache cache, final Properties properties) {
        return new BlockingCache(cache);
    }
}

I added decorator in xml config file ehache.xml from resources

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="ehcache.xsd"
         updateCheck="true"
         monitoring="autodetect"
         dynamicConfig="true">

    <cache name="findConcurrentById"
           eternal="false"
           maxEntriesLocalHeap="20000"
           timeToLiveSeconds="1800"
           memoryStoreEvictionPolicy="LRU">
        <cacheDecoratorFactory class="com.site.configuration.BlockingCacheDecoratorFactory"/>
    </cache>
</ehcache>

And I want to retrive cache in method

@Cacheable(value = "findConcurrentById", key = "#id", condition = "#result != null")
public Optional<Concurrent> findBy(Long id) {
    return concurrentRepo.findBy(id);
}

But still doesn't working. All I read doesn't explain more than what I already implemented. Can anyone explain me what is wrong at my code?