ApexPDP: Adding support to omit the (context) albums entry in an apex

policy model if it is empty. Implemented as a pair of JAXB XMLAdaters
Updated copyright, fixed somecheckstyle issues, refactored affected tests
& Merge

Issue-ID: POLICY-1802
Change-Id: Id68d9a524700f44c164939b7533f2d511b591e36
Signed-off-by: JohnKeeney <John.Keeney@est.tech>

6 files changed, 298 insertions, 48 deletions

diff --git a/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxArtifactKey.java b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxArtifactKey.java
index ad0e3fe8f..86c89c35e 100644
--- a/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxArtifactKey.java
+++ b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxArtifactKey.java
@@ -23,7 +23,6 @@ package org.onap.policy.apex.model.basicmodel.concepts;
 
 import java.util.ArrayList;
 import java.util.List;
-
 import javax.persistence.Column;
 import javax.persistence.Embeddable;
 import javax.xml.bind.annotation.XmlAccessType;
@@ -31,7 +30,6 @@ import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.XmlRootElement;
 import javax.xml.bind.annotation.XmlType;
-
 import org.onap.policy.apex.model.basicmodel.concepts.AxValidationResult.ValidationResult;
 import org.onap.policy.common.utils.validation.Assertions;
 
@@ -185,6 +183,16 @@ public class AxArtifactKey extends AxKey {
     }
 
     /**
+     * Check if the key is IDENTICAL to a null key.
+     *
+     * @return true, if the key is IDENTICAL to a null key
+     */
+    public boolean isNullKey() {
+        return this.getCompatibility(AxArtifactKey.getNullKey()).equals(AxKey.Compatibility.IDENTICAL);
+    }
+
+
+    /**
      * {@inheritDoc}.
      */
     @Override
@@ -352,4 +360,4 @@ public class AxArtifactKey extends AxKey {
         }
         return version.compareTo(other.version);
     }
-}
+}
\ No newline at end of file
diff --git a/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxModel.java b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxModel.java
index 03c578e21..e54b88078 100644
--- a/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxModel.java
+++ b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/concepts/AxModel.java
@@ -39,8 +39,10 @@ import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.XmlRootElement;
 import javax.xml.bind.annotation.XmlType;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
 import org.onap.policy.apex.model.basicmodel.concepts.AxValidationResult.ValidationResult;
+import org.onap.policy.apex.model.basicmodel.handling.KeyInfoMarshalFilter;
 import org.onap.policy.apex.model.basicmodel.service.ModelService;
 import org.onap.policy.common.utils.validation.Assertions;
 
@@ -79,6 +81,7 @@ public class AxModel extends AxConcept {
     @JoinColumns({ @JoinColumn(name = "keyInformationName", referencedColumnName = "name"),
             @JoinColumn(name = "keyInformationVersion", referencedColumnName = "version") })
     @XmlElement(name = "keyInformation", required = true)
+    @XmlJavaTypeAdapter(KeyInfoMarshalFilter.class)
     private AxKeyInformation keyInformation;
     // @formatter:on
 
diff --git a/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/handling/KeyInfoMarshalFilter.java b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/handling/KeyInfoMarshalFilter.java
new file mode 100644
index 000000000..41cf4df89
--- /dev/null
+++ b/model/basic-model/src/main/java/org/onap/policy/apex/model/basicmodel/handling/KeyInfoMarshalFilter.java
@@ -0,0 +1,104 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.model.basicmodel.handling;
+
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import javax.xml.bind.annotation.adapters.XmlAdapter;
+import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
+import org.onap.policy.apex.model.basicmodel.concepts.AxKey;
+import org.onap.policy.apex.model.basicmodel.concepts.AxKeyInfo;
+import org.onap.policy.apex.model.basicmodel.concepts.AxKeyInformation;
+
+/**
+ * This class implements a filter to prevent some keyinfo information being marshalled when a model is serialised.
+ */
+public class KeyInfoMarshalFilter extends XmlAdapter<AxKeyInformation, AxKeyInformation> {
+
+    private List<AxKey> filterList = new LinkedList<>();
+
+    /**
+     * Adds a key to the list to be filtered.
+     *
+     * @param key the key to add to the filter list
+     */
+    public void addFilterKey(AxKey key) {
+        filterList.add(key);
+    }
+
+    /**
+     * Remove a key from the list to be filtered.
+     *
+     * @param key the key to remove from the filter list
+     * @return true if the passed key was in the filter list and has been removed.
+     */
+    public boolean removeFilterKey(AxKey key) {
+        return filterList.remove(key);
+    }
+
+    /**
+     * Adds some keys to the list to be filtered.
+     *
+     * @param keys the keys to add to the filter list
+     */
+    public void addFilterKeys(Collection<? extends AxKey> keys) {
+        filterList.addAll(keys);
+    }
+
+    /**
+     * Decide whether to unmarshall some keyinfos - Always.
+     *
+     * @param val the keyinfo
+     * @return the keyinfo
+     * @throws Exception if there is some problem unmarshalling
+     * @see javax.xml.bind.annotation.adapters.XmlAdapter#unmarshal(Object)
+     */
+    @Override
+    public AxKeyInformation unmarshal(AxKeyInformation val) throws Exception {
+        return val;
+    }
+
+    /**
+     * Select which keyinfo entries will be marshalled - i.e. those not in the filter list.
+     *
+     * @param val the keyinfo
+     * @return the keyinfo
+     * @throws Exception if there is some problem with the marshalling
+     * @see javax.xml.bind.annotation.adapters.XmlAdapter#marshal(Object)
+     */
+    @Override
+    public AxKeyInformation marshal(AxKeyInformation val) throws Exception {
+        if (val == null || val.getKeyInfoMap() == null || val.getKeyInfoMap().isEmpty() || filterList.isEmpty() ) {
+            return val;
+        }
+        //create a new keyinfo clone to avoid removing keyinfo entries from the original model
+        AxKeyInformation ret = new AxKeyInformation(val);
+        Map<AxArtifactKey, AxKeyInfo> retmap = new TreeMap<>(ret.getKeyInfoMap());
+        for (AxKey key : filterList) {
+            retmap.remove(key);
+        }
+        ret.setKeyInfoMap(retmap);
+        return ret;
+    }
+}
diff --git a/model/basic-model/src/test/java/org/onap/policy/apex/model/basicmodel/concepts/AxKeyTest.java b/model/basic-model/src/test/java/org/onap/policy/apex/model/basicmodel/concepts/AxKeyTest.java
index c3c87b965..592933772 100644
--- a/model/basic-model/src/test/java/org/onap/policy/apex/model/basicmodel/concepts/AxKeyTest.java
+++ b/model/basic-model/src/test/java/org/onap/policy/apex/model/basicmodel/concepts/AxKeyTest.java
@@ -1,19 +1,20 @@
 /*
  * ============LICENSE_START=======================================================
  *  Copyright (C) 2016-2018 Ericsson. All rights reserved.
+ *  Modifications Copyright (C) 2019 Nordix Foundation.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
- * 
+ *
  * SPDX-License-Identifier: Apache-2.0
  * ============LICENSE_END=========================================================
  */
@@ -27,13 +28,8 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import java.lang.reflect.Field;
-
 import org.junit.Test;
-import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
-import org.onap.policy.apex.model.basicmodel.concepts.AxKey;
 import org.onap.policy.apex.model.basicmodel.concepts.AxKey.Compatibility;
-import org.onap.policy.apex.model.basicmodel.concepts.AxReferenceKey;
-import org.onap.policy.apex.model.basicmodel.concepts.AxValidationResult;
 
 public class AxKeyTest {
 
@@ -124,6 +120,16 @@ public class AxKeyTest {
         assertFalse(someKey0.equals(null));
         assertTrue(someKey0.equals(someKey0));
         assertFalse(((AxKey) someKey0).equals(new AxReferenceKey()));
+
+        AxArtifactKey nullKey0 = AxArtifactKey.getNullKey();
+        assertTrue(nullKey0.isNullKey());
+        AxArtifactKey nullKey1 = new AxArtifactKey();
+        assertTrue(nullKey1.isNullKey());
+        AxArtifactKey nullKey2 = new AxArtifactKey(AxKey.NULL_KEY_NAME,AxKey.NULL_KEY_VERSION);
+        assertTrue(nullKey2.isNullKey());
+        AxArtifactKey notnullKey = new AxArtifactKey("Blah",AxKey.NULL_KEY_VERSION);
+        assertFalse(notnullKey.isNullKey());
+
     }
 
 
diff --git a/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/concepts/AxPolicyModel.java b/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/concepts/AxPolicyModel.java
index ca7e7b335..3ad08a132 100644
--- a/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/concepts/AxPolicyModel.java
+++ b/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/concepts/AxPolicyModel.java
@@ -25,19 +25,20 @@ import java.util.List;
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.TreeSet;
-
 import javax.persistence.CascadeType;
 import javax.persistence.Entity;
 import javax.persistence.JoinColumn;
 import javax.persistence.JoinColumns;
 import javax.persistence.OneToOne;
 import javax.persistence.Table;
+import javax.xml.bind.Marshaller;
+import javax.xml.bind.Unmarshaller;
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.XmlRootElement;
 import javax.xml.bind.annotation.XmlType;
-
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
 import org.onap.policy.apex.model.basicmodel.concepts.AxConcept;
 import org.onap.policy.apex.model.basicmodel.concepts.AxKey;
@@ -47,6 +48,7 @@ import org.onap.policy.apex.model.basicmodel.concepts.AxReferenceKey;
 import org.onap.policy.apex.model.basicmodel.concepts.AxValidationMessage;
 import org.onap.policy.apex.model.basicmodel.concepts.AxValidationResult;
 import org.onap.policy.apex.model.basicmodel.concepts.AxValidationResult.ValidationResult;
+import org.onap.policy.apex.model.basicmodel.handling.KeyInfoMarshalFilter;
 import org.onap.policy.apex.model.basicmodel.service.ModelService;
 import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbum;
 import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbums;
@@ -55,6 +57,7 @@ import org.onap.policy.apex.model.contextmodel.concepts.AxContextSchemas;
 import org.onap.policy.apex.model.eventmodel.concepts.AxEvent;
 import org.onap.policy.apex.model.eventmodel.concepts.AxEvents;
 import org.onap.policy.apex.model.eventmodel.concepts.AxField;
+import org.onap.policy.apex.model.policymodel.handling.EmptyAlbumsAdapter;
 import org.onap.policy.common.utils.validation.Assertions;
 
 /**
@@ -108,7 +111,7 @@ import org.onap.policy.common.utils.validation.Assertions;
 @XmlRootElement(name = "apexPolicyModel", namespace = "http://www.onap.org/policy/apex-pdp")
 @XmlAccessorType(XmlAccessType.FIELD)
 @XmlType(name = "AxPolicyModel", namespace = "http://www.onap.org/policy/apex-pdp",
-        propOrder = {"policies", "tasks", "events", "albums", "schemas"})
+    propOrder = {"policies", "tasks", "events", "albums", "schemas"})
 
 public class AxPolicyModel extends AxModel {
     private static final String DOES_NOT_EXIST = " does not exist";
@@ -137,7 +140,8 @@ public class AxPolicyModel extends AxModel {
     @OneToOne(cascade = CascadeType.ALL)
     @JoinColumns({@JoinColumn(name = "albumsName", referencedColumnName = "name"),
             @JoinColumn(name = "albumsVersion", referencedColumnName = "version")})
-    @XmlElement(name = "albums", required = true)
+    @XmlElement(name = "albums", required = false )
+    @XmlJavaTypeAdapter(EmptyAlbumsAdapter.class)
     private AxContextAlbums albums;
 
     @OneToOne(cascade = CascadeType.ALL)
@@ -172,11 +176,11 @@ public class AxPolicyModel extends AxModel {
      */
     public AxPolicyModel(final AxArtifactKey key) {
         this(key, new AxContextSchemas(new AxArtifactKey(key.getName() + "_Schemas", key.getVersion())),
-                new AxKeyInformation(new AxArtifactKey(key.getName() + "_KeyInfo", key.getVersion())),
-                new AxEvents(new AxArtifactKey(key.getName() + "_Events", key.getVersion())),
-                new AxContextAlbums(new AxArtifactKey(key.getName() + "_Albums", key.getVersion())),
-                new AxTasks(new AxArtifactKey(key.getName() + "_Tasks", key.getVersion())),
-                new AxPolicies(new AxArtifactKey(key.getName() + "_Policies", key.getVersion())));
+            new AxKeyInformation(new AxArtifactKey(key.getName() + "_KeyInfo", key.getVersion())),
+            new AxEvents(new AxArtifactKey(key.getName() + "_Events", key.getVersion())),
+            new AxContextAlbums(new AxArtifactKey(key.getName() + "_Albums", key.getVersion())),
+            new AxTasks(new AxArtifactKey(key.getName() + "_Tasks", key.getVersion())),
+            new AxPolicies(new AxArtifactKey(key.getName() + "_Policies", key.getVersion())));
     }
 
     /**
@@ -243,7 +247,7 @@ public class AxPolicyModel extends AxModel {
      */
     public AxContextModel getContextModel() {
         return new AxContextModel(new AxArtifactKey(albums.getKey().getName() + "_Model", albums.getKey().getVersion()),
-                getSchemas(), getAlbums(), getKeyInformation());
+            getSchemas(), getAlbums(), getKeyInformation());
     }
 
     /**
@@ -374,8 +378,8 @@ public class AxPolicyModel extends AxModel {
             for (final AxField field : event.getFields()) {
                 if (getSchemas().get(field.getSchema()) == null) {
                     result.addValidationMessage(
-                            new AxValidationMessage(event.getKey(), this.getClass(), ValidationResult.INVALID,
-                                    "event field data type " + field.getSchema().getId() + DOES_NOT_EXIST));
+                        new AxValidationMessage(event.getKey(), this.getClass(), ValidationResult.INVALID,
+                            "event field data type " + field.getSchema().getId() + DOES_NOT_EXIST));
                 }
             }
         }
@@ -392,8 +396,8 @@ public class AxPolicyModel extends AxModel {
         for (final AxContextAlbum contextAlbum : albums.getAll(null)) {
             if (getSchemas().get(contextAlbum.getItemSchema()) == null) {
                 result.addValidationMessage(
-                        new AxValidationMessage(contextAlbum.getKey(), this.getClass(), ValidationResult.INVALID,
-                                "context album schema " + contextAlbum.getItemSchema().getId() + DOES_NOT_EXIST));
+                    new AxValidationMessage(contextAlbum.getKey(), this.getClass(), ValidationResult.INVALID,
+                        "context album schema " + contextAlbum.getItemSchema().getId() + DOES_NOT_EXIST));
             }
         }
         return result;
@@ -422,22 +426,21 @@ public class AxPolicyModel extends AxModel {
     private AxValidationResult validateTaskKeys(final AxTask task, AxValidationResult result) {
         for (final AxField field : task.getInputFieldSet()) {
             if (getSchemas().get(field.getSchema()) == null) {
-                result.addValidationMessage(
-                        new AxValidationMessage(task.getKey(), this.getClass(), ValidationResult.INVALID,
-                                "task input field schema " + field.getSchema().getId() + DOES_NOT_EXIST));
+                result.addValidationMessage(new AxValidationMessage(task.getKey(), this.getClass(),
+                    ValidationResult.INVALID, "task input field schema " + field.getSchema().getId() + DOES_NOT_EXIST));
             }
         }
         for (final AxField field : task.getOutputFieldSet()) {
             if (getSchemas().get(field.getSchema()) == null) {
                 result.addValidationMessage(
-                        new AxValidationMessage(task.getKey(), this.getClass(), ValidationResult.INVALID,
-                                "task output field schema " + field.getSchema().getId() + DOES_NOT_EXIST));
+                    new AxValidationMessage(task.getKey(), this.getClass(), ValidationResult.INVALID,
+                        "task output field schema " + field.getSchema().getId() + DOES_NOT_EXIST));
             }
         }
         for (final AxArtifactKey contextAlbumKey : task.getContextAlbumReferences()) {
             if (albums.get(contextAlbumKey) == null) {
                 result.addValidationMessage(new AxValidationMessage(task.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "task context album " + contextAlbumKey.getId() + DOES_NOT_EXIST));
+                    ValidationResult.INVALID, "task context album " + contextAlbumKey.getId() + DOES_NOT_EXIST));
             }
         }
         return result;
@@ -469,40 +472,40 @@ public class AxPolicyModel extends AxModel {
         for (final AxArtifactKey contextAlbumKey : state.getContextAlbumReferences()) {
             if (albums.get(contextAlbumKey) == null) {
                 result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "state context album " + contextAlbumKey.getId() + DOES_NOT_EXIST));
+                    ValidationResult.INVALID, "state context album " + contextAlbumKey.getId() + DOES_NOT_EXIST));
             }
         }
 
         final AxEvent triggerEvent = events.getEventMap().get(state.getTrigger());
         if (triggerEvent == null) {
             result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                    ValidationResult.INVALID, "state trigger event " + state.getTrigger().getId() + DOES_NOT_EXIST));
+                ValidationResult.INVALID, "state trigger event " + state.getTrigger().getId() + DOES_NOT_EXIST));
         }
 
         final AxTask defaultTask = tasks.getTaskMap().get(state.getDefaultTask());
         if (defaultTask == null) {
             result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                    ValidationResult.INVALID, "state default task " + state.getDefaultTask().getId() + DOES_NOT_EXIST));
+                ValidationResult.INVALID, "state default task " + state.getDefaultTask().getId() + DOES_NOT_EXIST));
         }
 
         // Check task input fields and event fields are compatible for default tasks with no task
         // selection logic
-        if (state.getTaskSelectionLogic().getKey().equals(AxReferenceKey.getNullKey()) && triggerEvent != null
-                && defaultTask != null) {
+        if (state.getTaskSelectionLogic().getKey().equals(AxReferenceKey.getNullKey())
+                && triggerEvent != null && defaultTask != null) {
             final Set<AxField> unhandledTaskInputFields = new TreeSet<>(defaultTask.getInputFieldSet());
             unhandledTaskInputFields.removeAll(triggerEvent.getFields());
             for (final AxField unhandledTaskInputField : unhandledTaskInputFields) {
                 result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "task input field " + unhandledTaskInputField + " for task "
-                                + defaultTask.getId() + " not in trigger event " + triggerEvent.getId()));
+                    ValidationResult.INVALID, "task input field " + unhandledTaskInputField + " for task "
+                        + defaultTask.getId() + " not in trigger event " + triggerEvent.getId()));
             }
         }
 
         for (final AxStateOutput stateOutput : state.getStateOutputs().values()) {
             if (events.getEventMap().get(stateOutput.getOutgingEvent()) == null) {
                 result.addValidationMessage(new AxValidationMessage(stateOutput.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "output event " + stateOutput.getOutgingEvent().getId()
-                                + " for state output " + stateOutput.getId() + DOES_NOT_EXIST));
+                    ValidationResult.INVALID, "output event " + stateOutput.getOutgingEvent().getId()
+                        + " for state output " + stateOutput.getId() + DOES_NOT_EXIST));
             }
         }
 
@@ -527,10 +530,10 @@ public class AxPolicyModel extends AxModel {
             final AxTask usedTask = tasks.getTaskMap().get(taskRefEntry.getKey());
             if (usedTask == null) {
                 result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "state task " + taskRefEntry.getKey().getId() + DOES_NOT_EXIST));
+                    ValidationResult.INVALID, "state task " + taskRefEntry.getKey().getId() + DOES_NOT_EXIST));
             } else {
                 AxStateOutput stateOutput =
-                        state.getStateOutputs().get(taskRefEntry.getValue().getOutput().getKey().getLocalName());
+                    state.getStateOutputs().get(taskRefEntry.getValue().getOutput().getKey().getLocalName());
                 validateEventTaskFieldCompatibilityOnStateOutput(state, usedTask, stateOutput, result);
             }
         }
@@ -549,14 +552,14 @@ public class AxPolicyModel extends AxModel {
             final AxStateOutput stateOutput, AxValidationResult result) {
         if (stateOutput == null) {
             result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                    ValidationResult.INVALID, "state output on task reference for task " + task.getId() + " is null"));
+                ValidationResult.INVALID, "state output on task reference for task " + task.getId() + " is null"));
 
         } else {
             final AxEvent usedEvent = events.getEventMap().get(stateOutput.getOutgingEvent());
             if (usedEvent == null) {
                 result.addValidationMessage(new AxValidationMessage(stateOutput.getKey(), this.getClass(),
-                        ValidationResult.INVALID, "output event " + stateOutput.getOutgingEvent().getId()
-                                + " for state output " + stateOutput.getId() + DOES_NOT_EXIST));
+                    ValidationResult.INVALID, "output event " + stateOutput.getOutgingEvent().getId()
+                        + " for state output " + stateOutput.getId() + DOES_NOT_EXIST));
             }
 
             if (task != null && usedEvent != null) {
@@ -564,14 +567,49 @@ public class AxPolicyModel extends AxModel {
                 unhandledTaskOutputFields.removeAll(usedEvent.getFields());
                 for (final AxField unhandledTaskOutputField : unhandledTaskOutputFields) {
                     result.addValidationMessage(new AxValidationMessage(state.getKey(), this.getClass(),
-                            ValidationResult.INVALID, "task output field " + unhandledTaskOutputField + " for task "
-                                    + task.getId() + " not in output event " + usedEvent.getId()));
+                        ValidationResult.INVALID, "task output field " + unhandledTaskOutputField + " for task "
+                            + task.getId() + " not in output event " + usedEvent.getId()));
                 }
             }
         }
     }
 
     /**
+     * When a model is unmarshalled from disk or from the database, if the albums field was missing a blank
+     * with a null key was added. This method is called by JAXB after unmarshalling and is
+     * used to insert an appropriate key
+     *
+     * @param unmarshaller the unmarshaller that is unmarshalling the model
+     * @param parent the parent object of this object in the unmarshaller
+     */
+    public void afterUnmarshal(final Unmarshaller unmarshaller, final Object parent) {
+        new EmptyAlbumsAdapter().doAfterUnmarshal(this);
+    }
+
+    /**
+     * When a model is marshalled from disk or database, if the albums field is empty/null, then the albums field
+     * is not emitted. If the (empty) albums field is not emitted then it's keyinfo should also be suppressed
+     * This method is called by JAXB before marshaling and is used to insert the appropriate filters
+     *
+     * @param marshaller the marshaller that is marshaller the model
+     * @throws Exception if there is a problem with the marshalling
+     */
+    public void beforeMarshal(final Marshaller marshaller) throws Exception {
+        EmptyAlbumsAdapter albumsfilter = new EmptyAlbumsAdapter();
+        marshaller.setAdapter(EmptyAlbumsAdapter.class, albumsfilter);
+        //get/create the keyinfofilter
+        KeyInfoMarshalFilter keyinfoFilter = marshaller.getAdapter(KeyInfoMarshalFilter.class);
+        if (keyinfoFilter == null) {
+            keyinfoFilter = new KeyInfoMarshalFilter();
+        }
+        //if the albumsfilter would filter out this model's albums add the album's key to the keyinfofilter
+        if (albumsfilter.marshal(this.albums) == null && this.albums != null) {
+            keyinfoFilter.addFilterKey(this.albums.getKey());
+        }
+        marshaller.setAdapter(keyinfoFilter);
+    }
+
+    /**
      * {@inheritDoc}.
      */
     @Override
@@ -711,4 +749,4 @@ public class AxPolicyModel extends AxModel {
         }
         return schemas.compareTo(other.schemas);
     }
-}
+}
\ No newline at end of file
diff --git a/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/handling/EmptyAlbumsAdapter.java b/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/handling/EmptyAlbumsAdapter.java
new file mode 100644
index 000000000..aa19edf0b
--- /dev/null
+++ b/model/policy-model/src/main/java/org/onap/policy/apex/model/policymodel/handling/EmptyAlbumsAdapter.java
@@ -0,0 +1,91 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.model.policymodel.handling;
+
+import javax.xml.bind.annotation.adapters.XmlAdapter;
+import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
+import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbums;
+import org.onap.policy.apex.model.policymodel.concepts.AxPolicyModel;
+
+/**
+ * This class makes the albums field optional in marshaled Policy Models.
+ * Empty albums are not marshaled to JSON/XML.
+ * When unmarshaled, if no albums value is present then a new empty albums entry is created.
+ *
+ * @author John Keeney (john.keeney@ericsson.com)
+ */
+public class EmptyAlbumsAdapter extends XmlAdapter<AxContextAlbums, AxContextAlbums> {
+
+
+    /**
+     * Decide whether to marshall a context albums entry. Non-empty context albums are always marshalled.
+     * Empty albums are filtered.
+     *
+     * @param albums the albums entry
+     * @return the albums entry, or null if empty
+     * @throws Exception if there is a problem with the marshalling
+     * @see javax.xml.bind.annotation.adapters.XmlAdapter#marshal(Object)
+     */
+    @Override
+    public AxContextAlbums marshal(AxContextAlbums albums) throws Exception {
+        if ((albums == null) || (albums.getAlbumsMap() == null) || (albums.getAlbumsMap().isEmpty())) {
+            return null;
+        } else {
+            return albums;
+        }
+    }
+
+    /**
+     * Decide whether to unmarshall a context albums entry - Always.
+     *
+     * @param val the albums entry
+     * @return the albums entry
+     * @throws Exception if there is a problem with the unmarshalling
+     * @see javax.xml.bind.annotation.adapters.XmlAdapter#unmarshal(Object)
+     */
+    @Override
+    public AxContextAlbums unmarshal(AxContextAlbums val) throws Exception {
+        return val;
+    }
+
+    /**
+     * After unmarshalling has completed the model's context albums entry may be null/empty or default.
+     * If so the key for the albums entry should updated to a sensible value and additional keyinfo
+     * information should then be added for that key
+     *
+     * @param policyModel the policy model containing the possibly empty context albums entry
+     * @see javax.xml.bind.annotation.adapters.XmlAdapter#unmarshal(Object)
+     */
+    public void doAfterUnmarshal(AxPolicyModel policyModel) {
+        AxArtifactKey nullkey = new AxArtifactKey();
+        AxArtifactKey blanknullalbumskey =
+            new AxArtifactKey(nullkey.getKey().getName() + "_Albums", nullkey.getKey().getVersion());
+        AxArtifactKey thisalbumskey = policyModel.getAlbums().getKey();
+        AxArtifactKey thismodelkey = policyModel.getKey();
+        AxContextAlbums thismodelalbums = policyModel.getAlbums();
+
+        if (nullkey.equals(thisalbumskey) || blanknullalbumskey.equals(thisalbumskey)) {
+            thismodelalbums.setKey(new AxArtifactKey(thismodelkey.getName() + "_Albums", thismodelkey.getVersion()));
+            policyModel.getKeyInformation().generateKeyInfo(thismodelalbums);
+        }
+    }
+
+}