Reuse caffeine cache key

Question

I have implemented a cache using caffeine. I want it to expire after 1 day, and that works fine. The problem, is that if I try to get data from the cache using a modified query (modified in terms of parameter values), I always get the same results. I want to get the same results only if I have executed a query with the same parameter values (e.g. same date range). My understanding is that I should not be re-using the same cache-key, but I m not sure how not to. This is the implementation:

@Service
public class SomeServiceImpl implements SomeService {
  private static final String CACHE_KEY = "some-key";
  private Cache<String, List<SomeVO>> someCache;



  public RecentHighestSlotWinsServiceImpl() {

    someCache= Caffeine.newBuilder().maximumSize(100).expireAfterWrite(1, TimeUnit.DAYS).build();
  }

  @Override
  public List<SomeVO> checkCacheForData(Instant startDate, Instant endDate) {

  List<SomeVO> someList= someCache.getIfPresent(CACHE_KEY);
  if (someList!= null) {
      return someList;
  } else {
      log.info("Loading from DB ");
      List<SomeVO> templateResult= getData(startDate, endDate);
      if (templateResult.isSuccessAndNotNull()) {
          someCache.put(CACHE_KEY, Objects.requireNonNull(templateResult.getData()));
      }
      return templateResult;
  }
}

Answer 1

Couple of ways to deal with this:

1. As @Louis Wasserman mentioned, have something like this:

import java.time.Instant;
import java.util.Objects;

public class CacheKey {
  private Instant startDate;
  private Instant endDate;

  public CacheKey() {
  }

  public CacheKey(Instant startDate, Instant endDate) {
    this.startDate = startDate;
    this.endDate = endDate;
  }

  public Instant getStartDate() {
    return startDate;
  }

  public void setStartDate(Instant startDate) {
    this.startDate = startDate;
  }

  public Instant getEndDate() {
    return endDate;
  }

  public void setEndDate(Instant endDate) {
    this.endDate = endDate;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o)
      return true;
    if (o == null || getClass() != o.getClass())
      return false;
    CacheKey cacheKey = (CacheKey) o;
    return Objects.equals(startDate, cacheKey.startDate) &&
        Objects.equals(endDate, cacheKey.endDate);
  }

  @Override
  public int hashCode() {
    return Objects.hash(startDate, endDate);
  }
}

and in your method checkCacheForData use:

@Service
public class SomeServiceImpl implements SomeService {
  private Cache<CacheKey, List<SomeVO>> someCache;



  public RecentHighestSlotWinsServiceImpl() {

    someCache= Caffeine.newBuilder().maximumSize(100).expireAfterWrite(1, TimeUnit.DAYS).build();
  }

  @Override
  public List<SomeVO> checkCacheForData(Instant startDate, Instant endDate) {

  List<SomeVO> someList= someCache.getIfPresent(new CacheKey(startDate,endDate));
  if (someList!= null) {
      return someList;
  } else {
      log.info("Loading from DB ");
      List<SomeVO> templateResult= getData(startDate, endDate);
      if (templateResult.isSuccessAndNotNull()) {
          someCache.put(new CacheKey(startDate,endDate), Objects.requireNonNull(templateResult.getData()));
      }
      return templateResult;
  }
}

2. Instead of Having a separate object you can concatenate the string representation of start date and end date and use that as cache key.

@Service
public class SomeServiceImpl implements SomeService {
  private Cache<String, List<SomeVO>> someCache;



  public RecentHighestSlotWinsServiceImpl() {

    someCache= Caffeine.newBuilder().maximumSize(100).expireAfterWrite(1, TimeUnit.DAYS).build();
  }

  @Override
  public List<SomeVO> checkCacheForData(Instant startDate, Instant endDate) {

String cacheKey = startDate.toString() + endDate.toString();
  List<SomeVO> someList= someCache.getIfPresent(cacheKey);
  if (someList!= null) {
      return someList;
  } else {
      log.info("Loading from DB ");
      List<SomeVO> templateResult= getData(startDate, endDate);
      if (templateResult.isSuccessAndNotNull()) {
          someCache.put(cacheKey, Objects.requireNonNull(templateResult.getData()));
      }
      return templateResult;
  }
}