Using reference maps for caches and listeners 2

ExecutionTimingAuditableLifecycleListenerGuava.java

package javasplitter;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.ExecutionException;

public class ExecutionTimingAuditableLifecycleListener implements AuditableLifecycleListener {

    private final StatsCollector statsCollector;

    private final LoadingCache<Auditable, Long> timedExecutionsCache = 
       CacheBuilder.newBuilder()
            .weakKeys()
            .build(
                    new CacheLoader<Auditable, Long>() {
                        @Override
                        public Long load(final Auditable key) throws Exception {
                            return System.currentTimeMillis();
                        }
                    }
            );

    public ExecutionTimingAuditableLifecycleListener(
      final StatsCollector statsCollector) {
        this.statsCollector = statsCollector;
    }

    @Override
    public void onValidationStart(final Auditable auditable) {
        try {
            this.timedExecutionsCache.get(auditable);
        } catch (ExecutionException e) {
            // not thrown
        }
    }

    @Override
    public void onValidationFinish(final Auditable auditable) {
        try {
            this.statsCollector.collectValidationStats(
              auditable.getClass(),
              System.currentTimeMillis() - this.timedExecutionsCache.get(auditable)
            );
        } catch (ExecutionException e) {
            // not thrown
        } finally {
            this.timedExecutionsCache.invalidate(auditable);
        }
    }

    @Override
    public void onProcessStart(final Auditable auditable) {
        try {
            this.timedExecutionsCache.get(auditable);
        } catch (ExecutionException e) {
            // not thrown
        }
    }

    @Override
    public void onProcessFinish(final Auditable auditable) {
        try {
            this.statsCollector.collectProcessStats(
               auditable.getClass(),
               System.currentTimeMillis() - this.timedExecutionsCache.get(auditable)
            );
        } catch (ExecutionException e) {
            // not thrown
        } finally {
            this.timedExecutionsCache.invalidate(auditable);
        }
    }
}