When there's no existing processor that does what you want, you can create one with InvokeScriptedProcessor.
import org.apache.commons.lang3.StringUtils
import org.apache.nifi.distributed.cache.client.DistributedMapCacheClient
import org.apache.nifi.distributed.cache.client.Serializer
import org.apache.nifi.distributed.cache.client.exception.SerializationException
import org.apache.nifi.expression.AttributeExpression