wro4j-maven-plugin/src/main/java/ro/isdc/wro/maven/plugin/support/ResourceChangeHandler.java
public void remember(final Resource resource) {
    final WroManager manager = getManagerFactory().create();
    final HashStrategy hashStrategy = manager.getHashStrategy();
    final UriLocatorFactory locatorFactory = manager.getUriLocatorFactory();

    if (rememberedSet.contains(resource.getUri())) {
      // only calculate fingerprints and check imports if not already done
      getLog().debug("Resource with uri '" + resource.getUri() + "' has already been updated in this run.");
    } else {
      try {
        final String fingerprint = hashStrategy.getHash(locatorFactory.locate(resource.getUri()));
        getBuildContextHolder().setValue(resource.getUri(), fingerprint);
        rememberedSet.add(resource.getUri());
        getLog().debug("Persist fingerprint for resource '" + resource.getUri() + "' : " + fingerprint);
        if (resource.getType() == ResourceType.CSS) {
          final Reader reader = new InputStreamReader(locatorFactory.locate(resource.getUri()));
          getLog().debug("Check @import directive from " + resource);
          // persist fingerprints in imported resources.
          persistFingerprintsForCssImports(resource, reader);
        }
      } catch (final IOException e) {
        getLog().debug("could not check fingerprint of resource: " + resource);
      }
    }
  }
public void remember(final Resource resource) {
    final WroManager manager = getManagerFactory().create();
    final HashStrategy hashStrategy = manager.getHashStrategy();
    final UriLocatorFactory locatorFactory = manager.getUriLocatorFactory();

    if (rememberedSet.contains(resource.getUri())) {
      // only calculate fingerprints and check imports if not already done
      getLog().debug("Resource with uri '" + resource.getUri() + "' has already been updated in this run.");
    } else {
      try {
        final String fingerprint = hashStrategy.getHash(locatorFactory.locate(resource.getUri()));
        getBuildContextHolder().setValue(resource.getUri(), fingerprint);
        rememberedSet.add(resource.getUri());
        getLog().debug("Persist fingerprint for resource '" + resource.getUri() + "' : " + fingerprint);
        if (resource.getType() == ResourceType.CSS) {
          final Reader reader = new InputStreamReader(locatorFactory.locate(resource.getUri()));
          getLog().debug("Check @import directive from " + resource);
          // persist fingerprints in imported resources.
          persistFingerprintsForCssImports(resource, reader);
        }
      } catch (final IOException e) {
        getLog().debug("could not check fingerprint of resource: " + resource);
      }
    }
  }
Will persist the information regarding the provided resource in some internal store. This information will be used
later to check if the resource is changed.

@param resource
{@link Resource} to touch.