diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/daos/CostCategoryDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/daos/CostCategoryDAO.java
index f95793502..8bccdfa18 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/daos/CostCategoryDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/daos/CostCategoryDAO.java
@@ -25,6 +25,7 @@ import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.apache.commons.lang.Validate;
 import org.hibernate.Criteria;
 import org.hibernate.criterion.Restrictions;
 import org.joda.time.LocalDate;
@@ -77,10 +78,7 @@ public class CostCategoryDAO extends IntegrationEntityDAO<CostCategory>
     @Override
     public CostCategory findUniqueByCode(String code)
             throws InstanceNotFoundException {
-        if (code == null) {
-            throw new InstanceNotFoundException(code, CostCategory.class
-                    .getName());
-        }
+        Validate.notNull(code);
 
         Criteria c = getSession().createCriteria(CostCategory.class).add(
                 Restrictions.eq("code", code).ignoreCase());
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReport.java b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReport.java
index 2970070e6..5211e097b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReport.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReport.java
@@ -27,6 +27,7 @@ import java.util.HashSet;
 import java.util.Set;
 
 import org.apache.commons.lang.StringUtils;
+import org.apache.commons.lang.Validate;
 import org.hibernate.validator.AssertTrue;
 import org.hibernate.validator.NotNull;
 import org.hibernate.validator.Valid;
@@ -325,10 +326,7 @@ public class WorkReport extends IntegrationEntity {
 
     public Label getLabelByType(LabelType type)
             throws InstanceNotFoundException {
-
-        if (type == null) {
-            throw new InstanceNotFoundException(type, LabelType.class.getName());
-        }
+        Validate.notNull(type);
 
         for (Label l : this.labels) {
             if (l.getType().getId().equals(type.getId())) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/ManageOrderElementAdvancesController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/ManageOrderElementAdvancesController.java
index 78d8d4447..c54abe010 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/ManageOrderElementAdvancesController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/ManageOrderElementAdvancesController.java
@@ -1361,7 +1361,7 @@ public class ManageOrderElementAdvancesController extends
                 .canRemoveOrChange(advanceMeasurement))) {
             if (value == null) {
                 advanceMeasurement.setDate(null);
-                ((Datebox) comp).setValue(value);
+                ((Datebox) comp).setValue(null);
                 throw new WrongValueException(comp,
                         _("The date is not valid, the date must be not empty"));
             } else {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
index c07c8302c..c00c81729 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
@@ -137,12 +137,10 @@ public abstract class AssignedMaterialsModel<T, A> implements
 
         categoryDAO.reattach(materialCategory);
         final MaterialCategory parent = materialCategory.getParent();
-        if (parent == null) {
-            if (!materialCategories.contains(parent, materialCategory)) {
+        if (!materialCategories.contains(parent, materialCategory)) {
+            if (parent == null) {
                 materialCategories.addToRoot(materialCategory);
-            }
-        } else {
-            if (!materialCategories.contains(parent, materialCategory)) {
+            } else {
                 addCategory(materialCategories, parent);
                 materialCategories.add(parent, materialCategory);
             }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/reports/TimeLineRequiredMaterialModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/reports/TimeLineRequiredMaterialModel.java
index 3ecf6eccf..ca39492b5 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/reports/TimeLineRequiredMaterialModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/reports/TimeLineRequiredMaterialModel.java
@@ -372,17 +372,14 @@ public class TimeLineRequiredMaterialModel implements
 
         categoryDAO.reattach(materialCategory);
         final MaterialCategory parent = materialCategory.getParent();
-        if (parent == null) {
-            if (!materialCategories.contains(parent, materialCategory)) {
+        if (!materialCategories.contains(parent, materialCategory)) {
+            if (parent == null) {
                 materialCategories.addToRoot(materialCategory);
-                addMaterials(materialCategories, materialCategory);
-            }
-        } else {
-            if (!materialCategories.contains(parent, materialCategory)) {
+            } else {
                 addCategory(materialCategories, parent);
                 materialCategories.add(parent, materialCategory);
-                addMaterials(materialCategories, materialCategory);
             }
+            addMaterials(materialCategories, materialCategory);
         }
     }
 
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
index 6b9c2d452..ec83af281 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/workreports/impl/WorkReportConverter.java
@@ -30,6 +30,7 @@ import java.util.Set;
 import javax.xml.datatype.XMLGregorianCalendar;
 
 import org.apache.commons.lang.StringUtils;
+import org.apache.commons.lang.Validate;
 import org.navalplanner.business.common.Registry;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.common.exceptions.ValidationException;
@@ -597,9 +598,7 @@ public final class WorkReportConverter {
     private static Label getLabelByLabelType(Set<Label> labels, LabelType type)
             throws InstanceNotFoundException {
 
-        if (type == null) {
-            throw new InstanceNotFoundException(type, LabelType.class.getName());
-        }
+        Validate.notNull(type);
 
         for (Label l : labels) {
             if (l.getType().equals(type)) {