fix(api): address Copilot review issues in Hubble 2.0 API adaptation

- SchemaTemplateAPI: add ensurePdModeEnabled() guard to all endpoints
  to prevent NPE when MetaManager is not initialized in standalone mode
- SchemaTemplateAPI: add null body check in create() and update() to
  return 400 instead of NPE/500 on missing request body
- GraphsAPI.listProfile: format default_update_time consistently with
  create_time using DATE_FORMATTER instead of raw Date serialization
- GraphsAPI.manage: guard value.getClass() against null action value
  to prevent NPE when building the validation error message
- GraphSpaceAPI.deleteDefaultRole: wrap HugeDefaultRole.valueOf() in
  try/catch to return 400 for invalid role values instead of 500
- GraphManager: add isPDEnabled() guard to all schema-template methods
  to prevent NPE when MetaManager is not available in standalone mode
- GraphManager.updateGraphNickname: propagate PD persistence failure to
  caller with in-memory rollback, preventing silent state inconsistency

Author: Yeaury

hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/profile/GraphsAPI.java

@@ -184,7 +184,13 @@ public Object listProfile(@Context GraphManager manager,
                 boolean isDefault = defaultGraphs.containsKey(graph);
                 profile.put("default", isDefault);
                 if (isDefault) {
-                    profile.put("default_update_time", defaultGraphs.get(graph));
+                    Date defaultUpdateTime = defaultGraphs.get(graph);
+                    if (defaultUpdateTime != null) {
+                        LocalDateTime ldt = defaultUpdateTime.toInstant()
+                                .atZone(ZoneId.systemDefault()).toLocalDateTime();
+                        profile.put("default_update_time",
+                                    DATE_FORMATTER.format(ldt));
+                    }
                 }
 
                 Date createTime = hg.createTime();
@@ -342,7 +348,7 @@ public Map<String, String> manage(@Context GraphManager manager,
         Object value = actionMap.get(GRAPH_ACTION);
         E.checkArgument(value instanceof String,
                         "Invalid action type '%s', must be string",
-                        value.getClass());
+                        value == null ? "null" : value.getClass().getSimpleName());
         String action = (String) value;
         switch (action) {
             case UPDATE:

hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/space/GraphSpaceAPI.java

@@ -231,8 +231,13 @@ public void deleteDefaultRole(@Context GraphManager manager,
             throw new ForbiddenException("Forbidden to delete role " + role);
         }
 
-        HugeDefaultRole defaultRole =
-                HugeDefaultRole.valueOf(role.toUpperCase());
+        HugeDefaultRole defaultRole;
+        try {
+            defaultRole = HugeDefaultRole.valueOf(role.toUpperCase());
+        } catch (IllegalArgumentException e) {
+            E.checkArgument(false, "Invalid role value '%s'", role);
+            defaultRole = null; // unreachable, satisfies compiler
+        }
         boolean hasGraph = defaultRole.equals(HugeDefaultRole.OBSERVER);
         E.checkArgument(!hasGraph || StringUtils.isNotEmpty(graph),
                         "Must set a graph for observer");

hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/space/SchemaTemplateAPI.java

@@ -66,6 +66,7 @@ public class SchemaTemplateAPI extends API {
     public Object list(@Context GraphManager manager,
                        @PathParam("graphspace") String graphSpace) {
         LOG.debug("List all schema templates for graph space {}", graphSpace);
+        ensurePdModeEnabled(manager);
 
         Set<String> templates = manager.schemaTemplates(graphSpace);
         return ImmutableMap.of("schema_templates", templates);
@@ -81,6 +82,7 @@ public Object get(@Context GraphManager manager,
                       @PathParam("name") String name) {
         LOG.debug("Get schema template by name '{}' for graph space {}",
                   name, graphSpace);
+        ensurePdModeEnabled(manager);
 
         return manager.serializer().writeSchemaTemplate(
                        schemaTemplate(manager, graphSpace, name));
@@ -97,6 +99,9 @@ public String create(@Context GraphManager manager,
                          JsonSchemaTemplate jsonSchemaTemplate) {
         LOG.debug("Create schema template {} for graph space: '{}'",
                   jsonSchemaTemplate, graphSpace);
+        ensurePdModeEnabled(manager);
+        E.checkArgumentNotNull(jsonSchemaTemplate,
+                               "Request body cannot be null or empty");
         jsonSchemaTemplate.checkCreate(false);
 
         E.checkArgument(manager.graphSpace(graphSpace) != null,
@@ -120,6 +125,7 @@ public void delete(@Context GraphManager manager,
                        @Context SecurityContext sc) {
         LOG.debug("Remove schema template by name '{}' for graph space '{}'",
                   name, graphSpace);
+        ensurePdModeEnabled(manager);
         E.checkArgument(manager.graphSpace(graphSpace) != null,
                         "The graph space '%s' is not exist", graphSpace);
 
@@ -148,6 +154,9 @@ public String update(@Context GraphManager manager,
                        @PathParam("name") String name,
                        @Context SecurityContext sc,
                        JsonSchemaTemplate jsonSchemaTemplate) {
+        ensurePdModeEnabled(manager);
+        E.checkArgumentNotNull(jsonSchemaTemplate,
+                               "Request body cannot be null or empty");
         jsonSchemaTemplate.checkUpdate();
 
         SchemaTemplate old = schemaTemplate(manager, graphSpace, name);

hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java

@@ -2226,8 +2226,13 @@ public void updateGraphNickname(String graphSpace, String graphName,
                 this.metaManager.notifyGraphUpdate(graphSpace, graphName);
             }
         } catch (Exception e) {
-            LOG.warn("Failed to persist nickname for graph '{}/{}': {}",
-                     graphSpace, graphName, e.getMessage());
+            // Roll back the in-memory change so that the runtime state stays
+            // consistent with what was actually persisted.
+            if (g != null) {
+                g.nickname(null);
+            }
+            throw new HugeException("Failed to persist nickname for graph " +
+                                    "'%s/%s'", e, graphSpace, graphName);
         }
     }
 
@@ -2240,19 +2245,35 @@ public String cluster() {
     }
 
     public Set<String> schemaTemplates(String graphSpace) {
+        if (!isPDEnabled()) {
+            throw new HugeException("Schema templates are not supported in " +
+                                    "standalone (non-PD) mode");
+        }
         return this.metaManager.schemaTemplates(graphSpace);
     }
 
     public void createSchemaTemplate(String graphSpace, SchemaTemplate template) {
+        if (!isPDEnabled()) {
+            throw new HugeException("Schema templates are not supported in " +
+                                    "standalone (non-PD) mode");
+        }
         checkSchemaTemplateName(template.name());
         this.metaManager.addSchemaTemplate(graphSpace, template);
     }
 
     public void dropSchemaTemplate(String graphSpace, String name) {
+        if (!isPDEnabled()) {
+            throw new HugeException("Schema templates are not supported in " +
+                                    "standalone (non-PD) mode");
+        }
         this.metaManager.removeSchemaTemplate(graphSpace, name);
     }
 
     public void updateSchemaTemplate(String graphSpace, SchemaTemplate template) {
+        if (!isPDEnabled()) {
+            throw new HugeException("Schema templates are not supported in " +
+                                    "standalone (non-PD) mode");
+        }
         this.metaManager.updateSchemaTemplate(graphSpace, template);
     }