oVirt · Artemi10 · Apr 29, 2025
@@ -54,4 +54,6 @@ public enum Messages {
     VALUE_OUT_OF_RANGE_DETAIL_TEMPLATE,
 
     NOT_SUPPORTED_REASON,
+
+    INCORRECT_FOLLOW_LINK
 }
@@ -24,6 +24,7 @@
 import org.ovirt.engine.api.restapi.invocation.CurrentManager;
 import org.ovirt.engine.api.restapi.logging.MessageBundle;
 import org.ovirt.engine.api.restapi.logging.Messages;
+import org.ovirt.engine.api.restapi.resource.exception.IncorrectFollowLinkException;
 import org.ovirt.engine.api.restapi.resource.utils.LinkFollower;
 import org.ovirt.engine.api.restapi.resource.utils.LinksTreeNode;
 import org.ovirt.engine.api.restapi.types.MappingLocator;
@@ -426,7 +427,13 @@ public final void follow (ActionableResource entity) {
             ParametersHelper.removeParameter(MAX);
             LinksTreeNode linksTree = linkFollower.createLinksTree(entity.getClass(), followValue);
             follow(entity, linksTree);
-            linkFollower.followLinks(entity, linksTree);
+            try {
+                linkFollower.followLinks(entity, linksTree);
+            } catch (IncorrectFollowLinkException e) {
+                throw new WebFaultException(e,
+                    localize(Messages.INCORRECT_FOLLOW_LINK, e.getLink(), e.getEntityName()),
+                    Response.Status.BAD_REQUEST);
+            }
         }
     }
 

@@ -0,0 +1,21 @@
+package org.ovirt.engine.api.restapi.resource.exception;
+
+public class IncorrectFollowLinkException extends RuntimeException {
+
+    private final String link;
+    private final String entityName;
+
+    public IncorrectFollowLinkException(String link, String entityName, Throwable cause) {
+        super(cause);
+        this.entityName = entityName;
+        this.link = link;
+    }
+
+    public String getLink() {
+        return link;
+    }
+
+    public String getEntityName() {
+        return entityName;
+    }
+}
@@ -15,6 +15,7 @@
 import org.ovirt.engine.api.model.Link;
 import org.ovirt.engine.api.restapi.resource.BaseBackendResource;
 import org.ovirt.engine.api.restapi.resource.ResourceLocator;
+import org.ovirt.engine.api.restapi.resource.exception.IncorrectFollowLinkException;
 import org.ovirt.engine.api.utils.EntityHelper;
 import org.ovirt.engine.api.utils.ReflectionHelper;
 
@@ -139,6 +140,10 @@ private void followLinks(List<ActionableResource> entities, LinksTreeNode node)
      * follow all links in the provided links-tree, recursively.
      */
     private void followLink(ActionableResource entity, LinksTreeNode node) {
+        if (entity == null || node == null) {
+            return;
+        }
+
         List<ActionableResource> nextStepEntities = new LinkedList<>();
         if (EntityHelper.isCollection(entity)) {
             nextStepEntities.addAll(fetchData((BaseResources) entity, node));
@@ -181,7 +186,7 @@ private List<ActionableResource> fetchData(BaseResources collectionEntity, Links
                 results.add(fetchData(entity, node));
             }
         } catch (Exception e) {
-            throw new IllegalStateException("Problem following '" + node.getElement() + "' link in " + collectionEntity.getClass().getSimpleName() + " entity.", e);
+            throw new IncorrectFollowLinkException(node.getElement(), collectionEntity.getClass().getSimpleName(), e);
         }
         return results;
     }
@@ -204,17 +209,19 @@ private ActionableResource fetchData(BaseResource entity, LinksTreeNode link) {
             String element = underscoreToCamelCase(link.getElement());
             if (link.isFollowed()) {
                 Method getter = ReflectionHelper.getGetter(entity, element);
-                return (ActionableResource) getter.invoke(entity);
+                return getter != null ? (ActionableResource) getter.invoke(entity) : null;
             } else {
                 String href = getHref((BaseResource) entity, link.getElement());
                 ActionableResource result = fetch(href);
-                Method setter = ReflectionHelper.getSetter(entity, element);
-                setter.invoke(entity, result);
+
+                if (result != null) {
+                    Method setter = ReflectionHelper.getSetter(entity, element);
+                    setter.invoke(entity, result);
+                }
                 return result;
             }
         } catch (Exception e) {
-            throw new IllegalStateException("Problem fetching '" + link.getElement() +
-                    "' from " + entity.getClass().getSimpleName(), e);
+            throw new IncorrectFollowLinkException(link.getElement(), entity.getClass().getSimpleName(), e);
         }
     }
 
@@ -243,15 +250,22 @@ private String getHref(BaseResource entity, String link) throws IllegalAccessExc
             return optional.get().getHref();
         } else { //assume this is not a sub-collection, since it wasn't found among links.
             Method getter = ReflectionHelper.getGetter(entity, underscoreToCamelCase(link));
+            if (getter == null) {
+                throw new IllegalStateException("Follow link '" + link + "' is incorrect.");
+            }
             BaseResource member = (BaseResource) getter.invoke(entity);
-            return member.getHref();
+            return member != null ? member.getHref() : null;
         }
     }
 
     /**
      * This scope of this method is 'protected' for testing purposes.
      */
     protected ActionableResource fetch(String href) {
+        if (href == null) {
+            return null;
+        }
+
         try {
             BaseBackendResource resource = resourceLocator.locateResource(href);
             //need to invoke the method in the resource annotated with @GET

@@ -25,3 +25,4 @@ VALUE_OUT_OF_RANGE_DETAIL_TEMPLATE=The value {0} of attribute ''{1}'' is outside
 DISK_UPDATE_NOT_PERMITTED=Updating disk attributes other than QCOW version is permitted only for disk-attachments, which reside under VMs.
 CPU_UPDATE_NOT_PERMITTED=Attempt to automatically configure CPU topology or pinning while CPU topology or pinning is also specified.
 NOT_SUPPORTED_REASON=The input is unsupported. {0} is not supported.
+INCORRECT_FOLLOW_LINK=Problem following {0} link in {1} entity.
@@ -3,6 +3,8 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.BeforeEach;
@@ -18,8 +20,10 @@
 import org.ovirt.engine.api.model.Nic;
 import org.ovirt.engine.api.model.Nics;
 import org.ovirt.engine.api.model.Vm;
+import org.ovirt.engine.api.model.Vms;
 import org.ovirt.engine.api.restapi.resource.BackendVmNicsResource;
 import org.ovirt.engine.api.restapi.resource.ResourceLocator;
+import org.ovirt.engine.api.restapi.resource.exception.IncorrectFollowLinkException;
 import org.ovirt.engine.api.restapi.resource.utils.LinkFollower;
 import org.ovirt.engine.api.restapi.resource.utils.LinksTreeNode;
 
@@ -38,7 +42,9 @@ public void setUp() {
         linkFollower = new LinkFollower(resourceLocator) {
             //override fetch() since it requires a real environment and would crash tests.
             protected ActionableResource fetch(String href) {
-                if (href.equals("/ovirt-engine/api/vms/63978315-2d17-4e67-b393-2ea60a8aeacb/nics")) {
+                if (href == null) {
+                    return null;
+                } else if (href.equals("/ovirt-engine/api/vms/63978315-2d17-4e67-b393-2ea60a8aeacb/nics")) {
                     return createNics();
                 } else if (href.equals("/ovirt-engine/api/vms/63978315-2d17-4e67-b393-2ea60a8aeacb/diskattachments")) {
                     return createDiskAttachments();
@@ -75,6 +81,47 @@ public void testFollowLinks() throws SecurityException, IllegalArgumentException
         assertNotNull(vm.getDiskAttachments().getDiskAttachments().get(2).getDisk());
     }
 
+    @Test
+    public void testFollowLinksIfFollowIsIncorrect() {
+        LinksTreeNode linksTree = linkFollower.createLinksTree(Vm.class, "incorrect_nics");
+        Vm vm = createVm();
+        IncorrectFollowLinkException actualException = assertThrows(
+            IncorrectFollowLinkException.class,
+            () -> linkFollower.followLinks(vm, linksTree)
+        );
+        assertEquals("incorrect_nics", actualException.getLink());
+        assertEquals("Vm", actualException.getEntityName());
+    }
+
+    @Test
+    public void testFollowLinksForCollectionEntityIfFollowIsIncorrect() {
+        LinksTreeNode linksTree = linkFollower.createLinksTree(Vm.class, "incorrect_nics");
+        Vms vms = createVms();
+        IncorrectFollowLinkException actualException = assertThrows(
+            IncorrectFollowLinkException.class,
+            () -> linkFollower.followLinks(vms, linksTree)
+        );
+        assertEquals("incorrect_nics", actualException.getLink());
+        assertEquals("Vms", actualException.getEntityName());
+    }
+
+    @Test
+    public void testFollowLinksIfFollowedEntityIsNull() {
+        LinksTreeNode linksTree = linkFollower.createLinksTree(Vm.class, "template");
+        Vm vm = createVm();
+        linkFollower.followLinks(vm, linksTree);
+        assertNull(vm.getTemplate());
+        assertNull(vm.getNics());
+        assertNull(vm.getDiskAttachments());
+    }
+
+    private Vms createVms() {
+        Vms vms = new Vms();
+        vms.getVms().add(createVm());
+        vms.getVms().add(createVm());
+        return vms;
+    }
+
     private Vm createVm() {
         Vm vm = new Vm();
         //add an irrelevant link