cache-configuration

/*
##################################################################################
##################################################################################
######### IF YOU FOUND THIS GIST USEFUL, PLEASE LEAVE A STAR. THANKS. ############
##################################################################################
##################################################################################
*/

import com.github.benmanes.caffeine.cache.Caffeine;
import org.springframework.cache.CacheManager;
import org.springframework.cache.caffeine.CaffeineCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class CacheConfiguration {

  @Bean
  public CacheManager cacheManager() {
    CaffeineCacheManager cacheManager = new CaffeineCacheManager("myCache");
    cacheManager.setCaffeine(Caffeine.newBuilder()
        .maximumSize(1000)
        .expireAfterAccess(Duration.ofHours(1)));

    return cacheManager;
  }

}

Reactive InMemory Caching Sample1.md

A "reactive" example of in-memory caching of information using CacheMono

In this example, I have created a service which returns the id of a tenant for a given alias either from cache or (if not found) calls a REST API to fetch and stores it in the cache.

service-using-cache

@Service
public class TenantService {

  private final WebClient webClient;
  private final CacheManager cacheManager;

  public TenantService(WebClient webClient, CacheManager cacheManager) {
    this.webClient = webClient;
    this.cacheManager = cacheManager;
  }

  public Mono<String> getTenantByAlias(String tenantAlias) {

    CacheMono.MonoCacheBuilderCacheMiss<String, String> cacheBuilderCacheMiss =
        CacheMono.lookup(key -> {
          Cache tenantCache = getTenantCache();
          Cache.ValueWrapper valueWrapper = tenantCache.get(key);
          if (valueWrapper != null) {
            System.out.println("Tenant found in cache: " + tenantAlias);
            return Mono.just((String) ((Signal) valueWrapper.get()).get()).map(Signal::next);
          } else {
            System.out.println("Calling tenant service to get tenant id for alias: " + tenantAlias);
            return Mono.empty();
          }
        }, tenantAlias);

    CacheMono.MonoCacheBuilderCacheWriter<String, String> cacheBuilderCacheWriter =
        cacheBuilderCacheMiss.onCacheMissResume(() -> makeRestCall(tenantAlias));

    return cacheBuilderCacheWriter.andWriteWith((key, value) -> Mono.fromRunnable(() -> {
      if (!value.isOnError()) {
        Cache tenantCache = getTenantCache();
        tenantCache.put(key, value);
      }
    }));
  }

  private Cache getTenantCache() {
    Cache tenantCache = cacheManager.getCache("myCache");
    if (tenantCache == null) {
      throw new RuntimeException("No such cache found in cache config. Recheck configuration.");
    }
    return tenantCache;
  }

  private Mono<String> makeRestCall(String tenantAlias) {

    return webClient.get()
        .uri(...)
        .retrieve()
        ....
        ....
  }



}