Fix NPE when accessing group concurrently

Closes #40368

Signed-off-by: vramik <vramik@redhat.com>

model/infinispan/src/main/java/org/keycloak/models/cache/infinispan/GroupAdapter.java

@@ -271,7 +271,8 @@ public class GroupAdapter implements GroupModel {
     @Override
     public Long getSubGroupsCount() {
         if (isUpdated()) return updated.getSubGroupsCount();
-        return getGroupModel().getSubGroupsCount();
+        GroupModel model = modelSupplier.get();
+        return model == null ? null : model.getSubGroupsCount();
     }
 
     @Override

model/infinispan/src/main/java/org/keycloak/models/cache/infinispan/entities/CachedGroup.java

@@ -58,6 +58,7 @@ public class CachedGroup extends AbstractRevisioned implements InRealm {
         this.type = group.getType();
     }
 
+    @Override
     public String getRealm() {
         return realm;
     }

services/src/main/java/org/keycloak/utils/GroupUtils.java

@@ -98,14 +98,4 @@ public class GroupUtils {
         rep.setAccess(groupsEvaluator.getAccess(groupTree));
         return rep;
     }
-
-    private static boolean groupMatchesSearchOrIsPathElement(GroupModel group, String search) {
-        if (StringUtil.isBlank(search)) {
-            return true;
-        }
-        if (group.getName().contains(search)) {
-            return true;
-        }
-        return group.getSubGroupsStream().findAny().isPresent();
-    }
 }

tests/base/src/test/java/org/keycloak/tests/admin/group/GroupTest.java

@@ -25,6 +25,7 @@ import jakarta.ws.rs.core.Response.Status;
 import org.apache.http.client.methods.CloseableHttpResponse;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.impl.client.CloseableHttpClient;
+import org.hamcrest.Matchers;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 import org.keycloak.admin.client.Keycloak;
@@ -76,6 +77,9 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.stream.IntStream;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.anEmptyMap;
@@ -90,6 +94,7 @@ 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.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 /**
  * @author <a href="mailto:mstrukel@redhat.com">Marko Strukelj</a>
@@ -109,6 +114,49 @@ public class GroupTest extends AbstractGroupTest {
     @InjectHttpClient
     CloseableHttpClient httpClient;
 
+    
+    @Test
+    public void createMultiDeleteMultiReadMulti() {
+        // create multiple groups
+        List<String> groupUuuids = new ArrayList<>();
+        IntStream.range(0, 100).forEach(groupIndex -> {
+            GroupRepresentation group = new GroupRepresentation();
+            group.setName("Test Group " + groupIndex);
+            try (Response response = managedRealm.admin().groups().add(group)) {
+                boolean created = response.getStatusInfo().getFamily() == Response.Status.Family.SUCCESSFUL;
+                if (created) {
+                    final String groupUuid = ApiUtil.getCreatedId(response);
+                    groupUuuids.add(groupUuid);
+                } else {
+                    fail("Failed to create group: " + response.getStatusInfo().getReasonPhrase());
+                }
+            }
+        });
+
+        AtomicBoolean deletedAll = new AtomicBoolean(false);
+        List<Exception> caughtExceptions = new CopyOnWriteArrayList<>();
+        // read groups in a separate thread
+        new Thread(() -> {
+            while (!deletedAll.get()) {
+                try {
+                    // just loading briefs
+                    managedRealm.admin().groups().groups(null, 0, Integer.MAX_VALUE, true);
+                } catch (Exception e) {
+
+                    caughtExceptions.add(e);
+                }
+            }
+        }).start();
+
+        // delete groups
+        groupUuuids.forEach(groupUuid -> {
+            managedRealm.admin().groups().group(groupUuid).remove();
+        });
+        deletedAll.set(true);
+
+        assertThat(caughtExceptions, Matchers.empty());
+    }
+
     // KEYCLOAK-2716 Can't delete client if its role is assigned to a group
     @Test
     public void testClientRemoveWithClientRoleGroupMapping() {