diff --git a/src/main/java/org/hisp/dhis/model/AttributeValue.java b/src/main/java/org/hisp/dhis/model/AttributeValue.java
index 551c07cf..e2a212f0 100644
--- a/src/main/java/org/hisp/dhis/model/AttributeValue.java
+++ b/src/main/java/org/hisp/dhis/model/AttributeValue.java
@@ -29,6 +29,7 @@
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Objects;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -39,7 +40,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class AttributeValue {
+public class AttributeValue implements Serializable {
   @JsonProperty private Attribute attribute;
 
   @JsonProperty private String value;
diff --git a/src/main/java/org/hisp/dhis/model/DataSetElement.java b/src/main/java/org/hisp/dhis/model/DataSetElement.java
index 03de30a7..438ba19c 100644
--- a/src/main/java/org/hisp/dhis/model/DataSetElement.java
+++ b/src/main/java/org/hisp/dhis/model/DataSetElement.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -35,7 +36,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class DataSetElement {
+public class DataSetElement implements Serializable {
   @JsonProperty private CategoryCombo categoryCombo;
 
   @JsonProperty private DataSet dataSet;
diff --git a/src/main/java/org/hisp/dhis/model/Dhis2Objects.java b/src/main/java/org/hisp/dhis/model/Dhis2Objects.java
index a626addf..f9341edf 100644
--- a/src/main/java/org/hisp/dhis/model/Dhis2Objects.java
+++ b/src/main/java/org/hisp/dhis/model/Dhis2Objects.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -55,7 +56,7 @@
 @Setter
 @Accessors(chain = true)
 @NoArgsConstructor
-public class Dhis2Objects {
+public class Dhis2Objects implements Serializable {
   @JsonProperty private List<AnalyticsTableHook> analyticsTableHooks = new ArrayList<>();
 
   @JsonProperty private List<Attribute> attributes = new ArrayList<>();
diff --git a/src/main/java/org/hisp/dhis/model/IdScheme.java b/src/main/java/org/hisp/dhis/model/IdScheme.java
index ac4037d6..0927bd90 100644
--- a/src/main/java/org/hisp/dhis/model/IdScheme.java
+++ b/src/main/java/org/hisp/dhis/model/IdScheme.java
@@ -27,13 +27,14 @@
  */
 package org.hisp.dhis.model;
 
+import java.io.Serializable;
 import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import org.apache.commons.lang3.Validate;
 import org.hisp.dhis.model.exception.IllegalArgumentFormatException;
 
-public class IdScheme {
+public class IdScheme implements Serializable {
   public static final IdScheme UID = new IdScheme(ObjectProperty.UID);
 
   public static final IdScheme CODE = new IdScheme(ObjectProperty.CODE);
diff --git a/src/main/java/org/hisp/dhis/model/OptionSetObjects.java b/src/main/java/org/hisp/dhis/model/OptionSetObjects.java
index b714412d..0527953d 100644
--- a/src/main/java/org/hisp/dhis/model/OptionSetObjects.java
+++ b/src/main/java/org/hisp/dhis/model/OptionSetObjects.java
@@ -30,6 +30,7 @@
 import static org.apache.commons.collections4.CollectionUtils.isNotEmpty;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -41,7 +42,7 @@
 @Setter
 @Accessors(chain = true)
 @NoArgsConstructor
-public class OptionSetObjects {
+public class OptionSetObjects implements Serializable {
   @JsonProperty private List<OptionSet> optionSets = new ArrayList<>();
 
   @JsonProperty private List<Option> options = new ArrayList<>();
diff --git a/src/main/java/org/hisp/dhis/model/ProgramObjects.java b/src/main/java/org/hisp/dhis/model/ProgramObjects.java
index 6bd98532..4ec79197 100644
--- a/src/main/java/org/hisp/dhis/model/ProgramObjects.java
+++ b/src/main/java/org/hisp/dhis/model/ProgramObjects.java
@@ -31,6 +31,7 @@
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -45,7 +46,7 @@
 @Setter
 @Accessors(chain = true)
 @NoArgsConstructor
-public class ProgramObjects {
+public class ProgramObjects implements Serializable {
   @JsonProperty private List<Program> programs = new ArrayList<>();
 
   @JsonProperty private List<ProgramSection> programSections = new ArrayList<>();
diff --git a/src/main/java/org/hisp/dhis/model/SystemInfo.java b/src/main/java/org/hisp/dhis/model/SystemInfo.java
index 2e7c4799..3c104058 100644
--- a/src/main/java/org/hisp/dhis/model/SystemInfo.java
+++ b/src/main/java/org/hisp/dhis/model/SystemInfo.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -37,7 +38,7 @@
 @Setter
 @NoArgsConstructor
 @AllArgsConstructor
-public class SystemInfo {
+public class SystemInfo implements Serializable {
   @JsonProperty private String version;
 
   @JsonProperty private String revision;
diff --git a/src/main/java/org/hisp/dhis/model/SystemSettings.java b/src/main/java/org/hisp/dhis/model/SystemSettings.java
index e6393e0a..c945e047 100644
--- a/src/main/java/org/hisp/dhis/model/SystemSettings.java
+++ b/src/main/java/org/hisp/dhis/model/SystemSettings.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -36,7 +37,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class SystemSettings {
+public class SystemSettings implements Serializable {
   @JsonProperty(value = "keyCalendar")
   private String calendar;
 
diff --git a/src/main/java/org/hisp/dhis/model/analytics/AnalyticsDimension.java b/src/main/java/org/hisp/dhis/model/analytics/AnalyticsDimension.java
index 079b616d..d723e934 100644
--- a/src/main/java/org/hisp/dhis/model/analytics/AnalyticsDimension.java
+++ b/src/main/java/org/hisp/dhis/model/analytics/AnalyticsDimension.java
@@ -27,11 +27,12 @@
  */
 package org.hisp.dhis.model.analytics;
 
+import java.io.Serializable;
 import lombok.AccessLevel;
 import lombok.NoArgsConstructor;
 
 @NoArgsConstructor(access = AccessLevel.PRIVATE)
-public class AnalyticsDimension {
+public class AnalyticsDimension implements Serializable {
   /** Data dimension identifier. */
   public static final String DATA_X = "dx";
 
diff --git a/src/main/java/org/hisp/dhis/model/analytics/AnalyticsKeyword.java b/src/main/java/org/hisp/dhis/model/analytics/AnalyticsKeyword.java
index d7214d4f..de72f5bc 100644
--- a/src/main/java/org/hisp/dhis/model/analytics/AnalyticsKeyword.java
+++ b/src/main/java/org/hisp/dhis/model/analytics/AnalyticsKeyword.java
@@ -27,11 +27,12 @@
  */
 package org.hisp.dhis.model.analytics;
 
+import java.io.Serializable;
 import lombok.AccessLevel;
 import lombok.NoArgsConstructor;
 
 @NoArgsConstructor(access = AccessLevel.PRIVATE)
-public final class AnalyticsKeyword {
+public final class AnalyticsKeyword implements Serializable {
   /** User org unit. */
   public static final String USER_ORGUNIT = "USER_ORGUNIT";
 
diff --git a/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistration.java b/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistration.java
index 41d32e59..c33426c2 100644
--- a/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistration.java
+++ b/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistration.java
@@ -31,6 +31,7 @@
 
 import com.fasterxml.jackson.annotation.JsonFormat;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -39,7 +40,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class CompleteDataSetRegistration {
+public class CompleteDataSetRegistration implements Serializable {
   @JsonProperty private String dataSet;
 
   @JsonProperty private String period;
diff --git a/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistrationImportOptions.java b/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistrationImportOptions.java
index 5db0452d..9e66efb6 100644
--- a/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistrationImportOptions.java
+++ b/src/main/java/org/hisp/dhis/model/completedatasetregistration/CompleteDataSetRegistrationImportOptions.java
@@ -27,6 +27,7 @@
  */
 package org.hisp.dhis.model.completedatasetregistration;
 
+import java.io.Serializable;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -37,7 +38,7 @@
 @Getter
 @Setter
 @NoArgsConstructor(access = AccessLevel.PRIVATE)
-public class CompleteDataSetRegistrationImportOptions {
+public class CompleteDataSetRegistrationImportOptions implements Serializable {
   /** Identifier property used for data sets in the response. Overrides idScheme. */
   private IdScheme dataSetIdScheme;
 
diff --git a/src/main/java/org/hisp/dhis/model/dashboard/Dashboard.java b/src/main/java/org/hisp/dhis/model/dashboard/Dashboard.java
index a582199a..098b3fe3 100644
--- a/src/main/java/org/hisp/dhis/model/dashboard/Dashboard.java
+++ b/src/main/java/org/hisp/dhis/model/dashboard/Dashboard.java
@@ -38,7 +38,6 @@
 @Setter
 @NoArgsConstructor
 public class Dashboard extends NameableObject {
-
   /**
    * Optional, only set if this dashboard is embedded and loaded from an external provider.
    *
diff --git a/src/main/java/org/hisp/dhis/model/datastore/DataStoreEntries.java b/src/main/java/org/hisp/dhis/model/datastore/DataStoreEntries.java
index 68fd7c3c..235156d9 100644
--- a/src/main/java/org/hisp/dhis/model/datastore/DataStoreEntries.java
+++ b/src/main/java/org/hisp/dhis/model/datastore/DataStoreEntries.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.datastore;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -38,6 +39,6 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class DataStoreEntries {
+public class DataStoreEntries implements Serializable {
   @JsonProperty private List<Map<String, Object>> entries = new ArrayList<>();
 }
diff --git a/src/main/java/org/hisp/dhis/model/datastore/EntryMetadata.java b/src/main/java/org/hisp/dhis/model/datastore/EntryMetadata.java
index 5117ab56..351e0c84 100644
--- a/src/main/java/org/hisp/dhis/model/datastore/EntryMetadata.java
+++ b/src/main/java/org/hisp/dhis/model/datastore/EntryMetadata.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.datastore;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import lombok.Getter;
 import lombok.Setter;
@@ -37,7 +38,7 @@
 @Getter
 @Setter
 @ToString
-public class EntryMetadata {
+public class EntryMetadata implements Serializable {
   @JsonProperty private String id;
 
   @JsonProperty private String namespace;
diff --git a/src/main/java/org/hisp/dhis/model/enrollment/Enrollment.java b/src/main/java/org/hisp/dhis/model/enrollment/Enrollment.java
index 87a11707..ddc8f832 100644
--- a/src/main/java/org/hisp/dhis/model/enrollment/Enrollment.java
+++ b/src/main/java/org/hisp/dhis/model/enrollment/Enrollment.java
@@ -29,6 +29,7 @@
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import java.util.List;
 import lombok.Getter;
@@ -42,7 +43,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class Enrollment {
+public class Enrollment implements Serializable {
   @JsonProperty private String enrollment;
 
   @JsonProperty private String program;
diff --git a/src/main/java/org/hisp/dhis/model/enrollment/EnrollmentsResult.java b/src/main/java/org/hisp/dhis/model/enrollment/EnrollmentsResult.java
index b689d0c5..2698472a 100644
--- a/src/main/java/org/hisp/dhis/model/enrollment/EnrollmentsResult.java
+++ b/src/main/java/org/hisp/dhis/model/enrollment/EnrollmentsResult.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.enrollment;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -37,7 +38,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class EnrollmentsResult {
+public class EnrollmentsResult implements Serializable {
   @JsonProperty private List<Enrollment> enrollments = new ArrayList<>();
 
   public EnrollmentsResult(List<Enrollment> enrollments) {
diff --git a/src/main/java/org/hisp/dhis/model/relationship/Relationship.java b/src/main/java/org/hisp/dhis/model/relationship/Relationship.java
index d56ab663..f7a541b3 100644
--- a/src/main/java/org/hisp/dhis/model/relationship/Relationship.java
+++ b/src/main/java/org/hisp/dhis/model/relationship/Relationship.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.relationship;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -38,7 +39,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class Relationship {
+public class Relationship implements Serializable {
   @JsonProperty private String relationship;
 
   @JsonProperty private String relationshipType;
diff --git a/src/main/java/org/hisp/dhis/model/relationship/RelationshipItem.java b/src/main/java/org/hisp/dhis/model/relationship/RelationshipItem.java
index 64d58a5e..8f0cab1b 100644
--- a/src/main/java/org/hisp/dhis/model/relationship/RelationshipItem.java
+++ b/src/main/java/org/hisp/dhis/model/relationship/RelationshipItem.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.relationship;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -40,7 +41,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class RelationshipItem {
+public class RelationshipItem implements Serializable {
   @JsonProperty private TrackedEntity trackedEntity;
 
   @JsonProperty private Event event;
diff --git a/src/main/java/org/hisp/dhis/model/relationship/RelationshipsResult.java b/src/main/java/org/hisp/dhis/model/relationship/RelationshipsResult.java
index 90af6351..19cb2806 100644
--- a/src/main/java/org/hisp/dhis/model/relationship/RelationshipsResult.java
+++ b/src/main/java/org/hisp/dhis/model/relationship/RelationshipsResult.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.relationship;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -37,7 +38,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class RelationshipsResult {
+public class RelationshipsResult implements Serializable {
   @JsonProperty private List<Relationship> relationships = new ArrayList<>();
 
   public RelationshipsResult(List<Relationship> relationships) {
diff --git a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntity.java b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntity.java
index e013245e..52dac51e 100644
--- a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntity.java
+++ b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntity.java
@@ -32,6 +32,7 @@
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
@@ -48,7 +49,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class TrackedEntity {
+public class TrackedEntity implements Serializable {
   @JsonProperty private String trackedEntity;
 
   @JsonProperty private String trackedEntityType;
diff --git a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityAttributeValue.java b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityAttributeValue.java
index eb6a3d96..43440902 100644
--- a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityAttributeValue.java
+++ b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityAttributeValue.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.trackedentity;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.Date;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -39,7 +40,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class TrackedEntityAttributeValue {
+public class TrackedEntityAttributeValue implements Serializable {
   @JsonProperty private String attribute;
 
   @JsonProperty private String displayName;
diff --git a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityTypeAttribute.java b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityTypeAttribute.java
index ce2839dd..d0f14309 100644
--- a/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityTypeAttribute.java
+++ b/src/main/java/org/hisp/dhis/model/trackedentity/TrackedEntityTypeAttribute.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.trackedentity;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -37,7 +38,7 @@
 @Setter
 @ToString
 @NoArgsConstructor
-public class TrackedEntityTypeAttribute {
+public class TrackedEntityTypeAttribute implements Serializable {
   @JsonProperty private String id;
 
   @JsonProperty private TrackedEntityAttribute trackedEntityAttribute;
diff --git a/src/main/java/org/hisp/dhis/model/tracker/TrackedEntityObjects.java b/src/main/java/org/hisp/dhis/model/tracker/TrackedEntityObjects.java
index 9f26c352..45a4219d 100644
--- a/src/main/java/org/hisp/dhis/model/tracker/TrackedEntityObjects.java
+++ b/src/main/java/org/hisp/dhis/model/tracker/TrackedEntityObjects.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.tracker;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
@@ -45,7 +46,7 @@
 @Accessors(chain = true)
 @ToString
 @NoArgsConstructor
-public class TrackedEntityObjects {
+public class TrackedEntityObjects implements Serializable {
   @JsonProperty private List<TrackedEntity> trackedEntities = new ArrayList<>();
 
   @JsonProperty private List<Enrollment> enrollments = new ArrayList<>();
diff --git a/src/main/java/org/hisp/dhis/model/user/UserMetadata.java b/src/main/java/org/hisp/dhis/model/user/UserMetadata.java
index ece90378..6b918ae9 100644
--- a/src/main/java/org/hisp/dhis/model/user/UserMetadata.java
+++ b/src/main/java/org/hisp/dhis/model/user/UserMetadata.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.user;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -35,7 +36,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class UserMetadata {
+public class UserMetadata implements Serializable {
   @JsonProperty private String id;
 
   @JsonProperty private String name;
diff --git a/src/main/java/org/hisp/dhis/model/user/UserSettings.java b/src/main/java/org/hisp/dhis/model/user/UserSettings.java
index e0673982..ca77c6eb 100644
--- a/src/main/java/org/hisp/dhis/model/user/UserSettings.java
+++ b/src/main/java/org/hisp/dhis/model/user/UserSettings.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.user;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
@@ -35,7 +36,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class UserSettings {
+public class UserSettings implements Serializable {
   @JsonProperty(value = "keyUiLocale")
   private String uiLocale;
 
diff --git a/src/main/java/org/hisp/dhis/model/validation/Validation.java b/src/main/java/org/hisp/dhis/model/validation/Validation.java
index 6fc4c039..0fe5ee83 100644
--- a/src/main/java/org/hisp/dhis/model/validation/Validation.java
+++ b/src/main/java/org/hisp/dhis/model/validation/Validation.java
@@ -28,6 +28,7 @@
 package org.hisp.dhis.model.validation;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -39,7 +40,7 @@
 @Getter
 @Setter
 @NoArgsConstructor
-public class Validation {
+public class Validation implements Serializable {
   @JsonProperty private List<ValidationRuleViolation> validationRuleViolations = new ArrayList<>();
   @JsonProperty private List<IdentifiableObject> commentRequiredViolations = new ArrayList<>();
 
diff --git a/src/main/java/org/hisp/dhis/model/validation/ValidationRuleViolation.java b/src/main/java/org/hisp/dhis/model/validation/ValidationRuleViolation.java
index e21f7a6f..29a77155 100644
--- a/src/main/java/org/hisp/dhis/model/validation/ValidationRuleViolation.java
+++ b/src/main/java/org/hisp/dhis/model/validation/ValidationRuleViolation.java
@@ -28,21 +28,32 @@
 package org.hisp.dhis.model.validation;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 import lombok.Setter;
 import org.hisp.dhis.model.CategoryOptionCombo;
 import org.hisp.dhis.model.OrgUnit;
 
 @Getter
 @Setter
-public class ValidationRuleViolation {
+@NoArgsConstructor
+public class ValidationRuleViolation implements Serializable {
   @JsonProperty private Integer id;
+
   @JsonProperty private ValidationRule validationRule;
+
   @JsonProperty private Period period;
+
   @JsonProperty private OrgUnit organisationUnit;
+
   @JsonProperty private CategoryOptionCombo attributeOptionCombo;
+
   @JsonProperty private String leftsideValue;
+
   @JsonProperty private String rightsideValue;
+
   @JsonProperty private Integer dayInPeriod;
+
   @JsonProperty private Boolean notificationSent;
 }
diff --git a/src/main/java/org/hisp/dhis/model/validation/ValidationSide.java b/src/main/java/org/hisp/dhis/model/validation/ValidationSide.java
index 72f82ed9..3b76f10c 100644
--- a/src/main/java/org/hisp/dhis/model/validation/ValidationSide.java
+++ b/src/main/java/org/hisp/dhis/model/validation/ValidationSide.java
@@ -28,15 +28,22 @@
 package org.hisp.dhis.model.validation;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.Serializable;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 import lombok.Setter;
 
 @Getter
 @Setter
-public class ValidationSide {
+@NoArgsConstructor
+public class ValidationSide implements Serializable {
   @JsonProperty private String expression;
+
   @JsonProperty private String description;
+
   @JsonProperty private String displayDescription;
+
   @JsonProperty private Boolean slidingWindow;
+
   @JsonProperty private String missingValueStrategy;
 }
diff --git a/src/test/java/org/hisp/dhis/TestFixture.java b/src/test/java/org/hisp/dhis/TestFixture.java
index 764b9626..84fead52 100644
--- a/src/test/java/org/hisp/dhis/TestFixture.java
+++ b/src/test/java/org/hisp/dhis/TestFixture.java
@@ -40,7 +40,7 @@ public final class TestFixture {
 
   public static final String V41_URL = "https://play.im.dhis2.org/stable-2-41-7";
 
-  public static final String V42_URL = "https://play.im.dhis2.org/stable-2-42-3-1";
+  public static final String V42_URL = "https://play.im.dhis2.org/stable-2-42-4";
 
   public static final String LOCAL_URL = "http://localhost/dhis";