Address some issues identified by FindBugs.

src/main/java/com/datastax/driver/core/schemabuilder/DropMaterializedView.java

@@ -4,7 +4,6 @@ import com.google.common.base.Optional;
 
 public class DropMaterializedView extends Drop {
 
-	private final String itemType = "MATERIALIZED VIEW";
 	private Optional<String> keyspaceName = Optional.absent();
 	private String itemName;
 	private boolean ifExists = true;
@@ -31,7 +30,7 @@ public class DropMaterializedView extends Drop {
 
 	@Override
 	public String buildInternal() {
-		StringBuilder dropStatement = new StringBuilder("DROP " + itemType + " ");
+		StringBuilder dropStatement = new StringBuilder("DROP MATERIALIZED VIEW ");
 		if (ifExists) {
 			dropStatement.append("IF EXISTS ");
 		}

src/main/java/net/helenus/core/AbstractEntityDraft.java

@@ -150,8 +150,8 @@ public abstract class AbstractEntityDraft<E> implements Drafted<E> {
 		Map<String, Object> combined;
 		if (entityMap != null && entityMap.size() > 0) {
 			combined = new HashMap<String, Object>(entityMap.size());
-			for (String key : entityMap.keySet()) {
-				combined.put(key, entityMap.get(key));
+			for (Map.Entry<String, Object> e : entityMap.entrySet()) {
+				combined.put(e.getKey(), e.getValue());
 			}
 		} else {
 			combined = new HashMap<String, Object>(backingMap.size());

src/main/java/net/helenus/core/AbstractUnitOfWork.java

@@ -124,10 +124,10 @@ public abstract class AbstractUnitOfWork<E extends Exception> implements UnitOfW
 		String database = "";
 		if (databaseTime.size() > 0) {
 			List<String> dbt = new ArrayList<>(databaseTime.size());
-			for (String name : databaseTime.keySet()) {
-				double t = databaseTime.get(name) / 1000.0;
+			for (Map.Entry<String, Double> dt : databaseTime.entrySet()) {
+				double t = dt.getValue() / 1000.0;
 				d += t;
-				dbt.add(String.format("%s took %,.3fms %,2.2f%%", name, t, (t / e) * 100.0));
+				dbt.add(String.format("%s took %,.3fms %,2.2f%%", dt.getKey(), t, (t / e) * 100.0));
 			}
 			double fd = (d / e) * 100.0;
 			database = String.format(", %d quer%s (%,.3fms %,2.2f%% - %s)", databaseLookups,
@@ -293,12 +293,13 @@ public abstract class AbstractUnitOfWork<E extends Exception> implements UnitOfW
 				parent.cacheMisses += cacheMisses;
 				parent.databaseLookups += databaseLookups;
 				parent.cacheLookupTime += cacheLookupTime;
-				for (String name : databaseTime.keySet()) {
+				for (Map.Entry<String, Double> dt : databaseTime.entrySet()) {
+					String name = dt.getKey();
 					if (parent.databaseTime.containsKey(name)) {
 						double t = parent.databaseTime.get(name);
-						parent.databaseTime.put(name, t + databaseTime.get(name));
+						parent.databaseTime.put(name, t + dt.getValue());
 					} else {
-						parent.databaseTime.put(name, databaseTime.get(name));
+						parent.databaseTime.put(name, dt.getValue());
 					}
 				}
 			}

src/main/java/net/helenus/core/HelenusSession.java

@@ -335,8 +335,7 @@ public final class HelenusSession extends AbstractSessionOperations implements C
 			return uow.begin();
 		} catch (NoSuchMethodException | InvocationTargetException | InstantiationException
 				| IllegalAccessException e) {
-			throw new HelenusException(
-					String.format("Unable to instantiate {} as a UnitOfWork.", unitOfWorkClass.getSimpleName()), e);
+			throw new HelenusException(String.format("Unable to instantiate %s as a UnitOfWork.", unitOfWorkClass.getSimpleName()), e);
 		}
 	}
 
@@ -698,6 +697,9 @@ public final class HelenusSession extends AbstractSessionOperations implements C
 			case UDT :
 				execute(SchemaUtil.dropUserType(entity), true);
 				break;
+
+			default:
+				throw new HelenusException("Unknown entity type.");
 		}
 	}
 }

src/main/java/net/helenus/core/SchemaUtil.java

@@ -167,10 +167,6 @@ public final class SchemaUtil {
 			throw new HelenusMappingException("expected view entity " + entity);
 		}
 
-		if (entity == null) {
-			throw new HelenusMappingException("no entity or table to select data");
-		}
-
 		List<HelenusPropertyNode> props = new ArrayList<HelenusPropertyNode>();
 		entity.getOrderedProperties().stream().map(p -> new HelenusPropertyNode(p, Optional.empty()))
 				.forEach(p -> props.add(p));

src/main/java/net/helenus/core/cache/CacheUtil.java

@@ -8,7 +8,7 @@ public class CacheUtil {
 
 	public static List<String[]> combinations(List<String> items) {
 		int n = items.size();
-		if (n > 20 || n < 0)
+		if (n > 20)
 			throw new IllegalArgumentException(n + " is out of range");
 		long e = Math.round(Math.pow(2, n));
 		List<String[]> out = new ArrayList<String[]>((int) e - 1);

src/main/java/net/helenus/mapping/value/StatementColumnValuePreparer.java

@@ -44,13 +44,10 @@ public final class StatementColumnValuePreparer implements ColumnValuePreparer {
 
 		HelenusValidator.INSTANCE.validate(prop, value);
 
-		if (value != null) {
+		Optional<Function<Object, Object>> converter = prop.getWriteConverter(repository);
 
-			Optional<Function<Object, Object>> converter = prop.getWriteConverter(repository);
-
-			if (converter.isPresent()) {
-				value = converter.get().apply(value);
-			}
+		if (converter.isPresent()) {
+			value = converter.get().apply(value);
 		}
 
 		return value;

src/main/java/net/helenus/mapping/value/ValueProviderMap.java

@@ -111,13 +111,17 @@ public final class ValueProviderMap implements Map<String, Object> {
 
 	@Override
 	public Set<java.util.Map.Entry<String, Object>> entrySet() {
-		throwShouldNeverCall("entrySet()");
-		return null;
+		return entity.getOrderedProperties()
+				.stream()
+				.map(p -> {
+					return new ValueProviderMap.Entry<String, Object>(p.getPropertyName(),
+							valueProvider.getColumnValue(source, -1, p, immutable));
+				}).collect(Collectors.toSet());
 	}
 
-	private void throwShouldNeverCall(String methodName) {
+	private static void throwShouldNeverCall(String methodName) {
 		throw new HelenusMappingException(String.format(
-				"the method {} should never be called on an instance of a Helenus ValueProviderMap", methodName));
+				"the method %s should never be called on an instance of a Helenus ValueProviderMap", methodName));
 	}
 
 	@Override
@@ -125,6 +129,15 @@ public final class ValueProviderMap implements Map<String, Object> {
 		return source.toString();
 	}
 
+	@Override
+	public int hashCode() {
+		int result = source.hashCode();
+		result = 31 * result + valueProvider.hashCode();
+		result = 31 * result + entity.hashCode();
+		result = 31 * result + (immutable ? 1 : 0);
+		return result;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o)
@@ -135,10 +148,37 @@ public final class ValueProviderMap implements Map<String, Object> {
 		Map that = (Map) o;
 		if (this.size() != that.size())
 			return false;
-		for (String key : this.keySet())
-			if (!this.get(key).equals(that.get(key)))
+		for (Map.Entry<String, Object> e : this.entrySet())
+			if (!e.getValue().equals(that.get(e.getKey())))
 				return false;
 
 		return true;
 	}
+
+	public static class Entry<K, V> implements Map.Entry<K, V> {
+
+		private final K key;
+		private final V value;
+
+		public Entry(K key, V value) {
+			this.key = key;
+			this.value = value;
+		}
+
+		@Override
+		public K getKey() {
+			return key;
+		}
+
+		@Override
+		public V getValue() {
+			return value;
+		}
+
+		@Override
+		public V setValue(V value) {
+			throwShouldNeverCall("Entry.setValue()");
+			return null;
+		}
+	}
 }

src/test/java/net/helenus/test/integration/core/unitofwork/UnitOfWorkTest.java

@@ -173,9 +173,9 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
                     .uncached()
                     .sync().orElse(null);
 
-            Assert.assertNotEquals(w5, w2); // Not the same instance
-            Assert.assertTrue(w2.equals(w5)); // But they have the same values
-            Assert.assertFalse(w5.equals(w2)); // TODO(gburd): should also work
+            Assert.assertNotEquals(w5, w2); // Not the same instance,
+            Assert.assertTrue(w2.equals(w5)); // but they have the same values,
+            Assert.assertFalse(w5.equals(w2)); // regardless of the order when comparing.
             Assert.assertEquals(w5.name(), "Bill");
 
             uow.commit().andThen(() -> {