fix(server): keep schema ~create_time as Date after reload

hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/schema/SchemaElement.java

@@ -27,6 +27,7 @@
 import org.apache.hugegraph.type.Nameable;
 import org.apache.hugegraph.type.Typeable;
 import org.apache.hugegraph.type.define.SchemaStatus;
+import org.apache.hugegraph.util.DateUtil;
 import org.apache.hugegraph.util.E;
 import org.apache.tinkerpop.gremlin.structure.Graph;
 
@@ -99,11 +100,37 @@ public Map<String, Object> userdata() {
     public void userdata(String key, Object value) {
         E.checkArgumentNotNull(key, "userdata key");
         E.checkArgumentNotNull(value, "userdata value");
-        this.userdata.put(key, value);
+        this.userdata.put(key, normalizeUserdataValue(key, value));
     }
 
     public void userdata(Userdata userdata) {
-        this.userdata.putAll(userdata);
+        E.checkArgumentNotNull(userdata, "userdata");
+        for (Map.Entry<String, Object> e : userdata.entrySet()) {
+            this.userdata.put(e.getKey(),
+                              normalizeUserdataValue(e.getKey(), e.getValue()));
+        }
+    }
+
+    /**
+     * Normalize internal userdata values whose runtime type can diverge from
+     * their serialized form. The only such key today is
+     * {@link Userdata#CREATE_TIME}: it is written as a {@link java.util.Date}
+     * but persisted as a formatted JSON string by the backend serializers,
+     * and Jackson cannot re-type a value to {@code Date} when the target is
+     * a raw {@code Map}. This method restores the original type after
+     * deserialization. Idempotent for values already of the expected type.
+     */
+    private static Object normalizeUserdataValue(String key, Object value) {
+        if (Userdata.CREATE_TIME.equals(key) && value instanceof String) {
+            try {
+                return DateUtil.parse((String) value);
+            } catch (RuntimeException e) {
+                throw new IllegalArgumentException(String.format(
+                          "Invalid userdata '%s' value: '%s'",
+                          Userdata.CREATE_TIME, value), e);
+            }
+        }
+        return value;
     }
 
     public void removeUserdata(String key) {

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/unit/UnitTestSuite.java

@@ -43,6 +43,7 @@
 import org.apache.hugegraph.unit.core.RangeTest;
 import org.apache.hugegraph.unit.core.RolePermissionTest;
 import org.apache.hugegraph.unit.core.RowLockTest;
+import org.apache.hugegraph.unit.core.SchemaElementTest;
 import org.apache.hugegraph.unit.core.SecurityManagerTest;
 import org.apache.hugegraph.unit.core.SerialEnumTest;
 import org.apache.hugegraph.unit.core.SystemSchemaStoreTest;
@@ -64,6 +65,7 @@
 import org.apache.hugegraph.unit.serializer.StoreSerializerTest;
 import org.apache.hugegraph.unit.serializer.TableBackendEntryTest;
 import org.apache.hugegraph.unit.serializer.TextBackendEntryTest;
+import org.apache.hugegraph.unit.serializer.TextSerializerTest;
 import org.apache.hugegraph.unit.store.RamIntObjectMapTest;
 import org.apache.hugegraph.unit.util.CompressUtilTest;
 import org.apache.hugegraph.unit.util.JsonUtilTest;
@@ -127,6 +129,7 @@
         SystemSchemaStoreTest.class,
         RoleElectionStateMachineTest.class,
         HugeGraphAuthProxyTest.class,
+        SchemaElementTest.class,
 
         /* serializer */
         BytesBufferTest.class,
@@ -137,6 +140,7 @@
         BinarySerializerTest.class,
         BinaryScatterSerializerTest.class,
         StoreSerializerTest.class,
+        TextSerializerTest.class,
 
         /* cassandra */
         CassandraTest.class,

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/unit/core/SchemaElementTest.java

@@ -0,0 +1,125 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.hugegraph.unit.core;
+
+import java.util.Date;
+
+import org.apache.hugegraph.backend.id.IdGenerator;
+import org.apache.hugegraph.schema.PropertyKey;
+import org.apache.hugegraph.schema.SchemaElement;
+import org.apache.hugegraph.schema.Userdata;
+import org.apache.hugegraph.testutil.Assert;
+import org.apache.hugegraph.util.DateUtil;
+import org.junit.Test;
+
+public class SchemaElementTest {
+
+    private static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss.SSS";
+
+    private static SchemaElement newSchema() {
+        return new PropertyKey(null, IdGenerator.of(1L), "test");
+    }
+
+    @Test
+    public void testSingleSetterNormalizesCreateTimeStringToDate() {
+        SchemaElement schema = newSchema();
+        String formatted = "2026-05-14 10:11:12.345";
+
+        schema.userdata(Userdata.CREATE_TIME, formatted);
+
+        Object value = schema.userdata().get(Userdata.CREATE_TIME);
+        Assert.assertTrue("CREATE_TIME should be a Date, was " +
+                          (value == null ? "null" : value.getClass()),
+                          value instanceof Date);
+        Assert.assertEquals(DateUtil.parse(formatted, DATE_FORMAT), value);
+    }
+
+    @Test
+    public void testSingleSetterKeepsCreateTimeDateUnchanged() {
+        SchemaElement schema = newSchema();
+        Date now = DateUtil.now();
+
+        schema.userdata(Userdata.CREATE_TIME, now);
+
+        Assert.assertSame(now, schema.userdata().get(Userdata.CREATE_TIME));
+    }
+
+    @Test
+    public void testSingleSetterRejectsInvalidCreateTimeString() {
+        SchemaElement schema = newSchema();
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            schema.userdata(Userdata.CREATE_TIME, "not-a-date");
+        }, e -> {
+            Assert.assertContains(Userdata.CREATE_TIME, e.getMessage());
+            Assert.assertContains("not-a-date", e.getMessage());
+        });
+    }
+
+    @Test
+    public void testSingleSetterLeavesOtherStringKeysUntouched() {
+        SchemaElement schema = newSchema();
+
+        schema.userdata("note", "2026-05-14 10:11:12.345");
+
+        Object value = schema.userdata().get("note");
+        Assert.assertTrue(value instanceof String);
+        Assert.assertEquals("2026-05-14 10:11:12.345", value);
+    }
+
+    @Test
+    public void testBulkSetterNormalizesCreateTimeAndKeepsOtherEntries() {
+        SchemaElement schema = newSchema();
+        Userdata bulk = new Userdata();
+        String formatted = "2026-05-14 10:11:12.345";
+        bulk.put(Userdata.CREATE_TIME, formatted);
+        bulk.put("note", "hello");
+        bulk.put("count", 42);
+
+        schema.userdata(bulk);
+
+        Object createTime = schema.userdata().get(Userdata.CREATE_TIME);
+        Assert.assertTrue(createTime instanceof Date);
+        Assert.assertEquals(DateUtil.parse(formatted, DATE_FORMAT), createTime);
+        Assert.assertEquals("hello", schema.userdata().get("note"));
+        Assert.assertEquals(42, schema.userdata().get("count"));
+    }
+
+    @Test
+    public void testBulkSetterKeepsCreateTimeDateUnchanged() {
+        SchemaElement schema = newSchema();
+        Userdata bulk = new Userdata();
+        Date now = DateUtil.now();
+        bulk.put(Userdata.CREATE_TIME, now);
+
+        schema.userdata(bulk);
+
+        Assert.assertSame(now, schema.userdata().get(Userdata.CREATE_TIME));
+    }
+
+    @Test
+    public void testBulkSetterRejectsNullUserdata() {
+        SchemaElement schema = newSchema();
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            schema.userdata(null);
+        }, e -> {
+            Assert.assertContains("userdata", e.getMessage());
+        });
+    }
+}

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/unit/serializer/BinarySerializerTest.java

@@ -17,15 +17,21 @@
 
 package org.apache.hugegraph.unit.serializer;
 
+import java.util.Date;
+
+import org.apache.hugegraph.backend.id.IdGenerator;
 import org.apache.hugegraph.backend.serializer.BinarySerializer;
 import org.apache.hugegraph.backend.store.BackendEntry;
 import org.apache.hugegraph.config.HugeConfig;
+import org.apache.hugegraph.schema.PropertyKey;
+import org.apache.hugegraph.schema.Userdata;
 import org.apache.hugegraph.structure.HugeEdge;
 import org.apache.hugegraph.structure.HugeVertex;
 import org.apache.hugegraph.testutil.Assert;
 import org.apache.hugegraph.testutil.Whitebox;
 import org.apache.hugegraph.unit.BaseUnitTest;
 import org.apache.hugegraph.unit.FakeObjects;
+import org.apache.hugegraph.util.DateUtil;
 import org.junit.Test;
 
 public class BinarySerializerTest extends BaseUnitTest {
@@ -105,6 +111,28 @@ public void testVertexForPartition() {
         Assert.assertNull(ser.readVertex(edge.graph(), null));
     }
 
+    @Test
+    public void testPropertyKeyUserdataCreateTimeRoundTripsAsDate() {
+        HugeConfig config = FakeObjects.newConfig();
+        BinarySerializer ser = new BinarySerializer(config);
+
+        FakeObjects objects = new FakeObjects();
+        PropertyKey original = objects.newPropertyKey(IdGenerator.of(1L),
+                                                      "name");
+        Date created = DateUtil.parse("2026-05-14 10:11:12.345",
+                                      "yyyy-MM-dd HH:mm:ss.SSS");
+        original.userdata(Userdata.CREATE_TIME, created);
+
+        BackendEntry entry = ser.writePropertyKey(original);
+        PropertyKey reloaded = ser.readPropertyKey(objects.graph(), entry);
+
+        Object value = reloaded.userdata().get(Userdata.CREATE_TIME);
+        Assert.assertTrue("CREATE_TIME should be a Date after round-trip, " +
+                          "was " + (value == null ? "null" : value.getClass()),
+                          value instanceof Date);
+        Assert.assertEquals(created, value);
+    }
+
     @Test
     public void testEdgeForPartition() {
         BinarySerializer ser = new BinarySerializer(true, true, true);

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/unit/serializer/TextSerializerTest.java

@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.hugegraph.unit.serializer;
+
+import java.util.Date;
+
+import org.apache.hugegraph.backend.id.IdGenerator;
+import org.apache.hugegraph.backend.serializer.TextSerializer;
+import org.apache.hugegraph.backend.store.BackendEntry;
+import org.apache.hugegraph.config.HugeConfig;
+import org.apache.hugegraph.schema.PropertyKey;
+import org.apache.hugegraph.schema.Userdata;
+import org.apache.hugegraph.testutil.Assert;
+import org.apache.hugegraph.unit.BaseUnitTest;
+import org.apache.hugegraph.unit.FakeObjects;
+import org.apache.hugegraph.util.DateUtil;
+import org.junit.Test;
+
+public class TextSerializerTest extends BaseUnitTest {
+
+    private static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss.SSS";
+
+    @Test
+    public void testPropertyKeyUserdataCreateTimeRoundTripsAsDate() {
+        HugeConfig config = FakeObjects.newConfig();
+        TextSerializer ser = new TextSerializer(config);
+
+        FakeObjects objects = new FakeObjects();
+        PropertyKey original = objects.newPropertyKey(IdGenerator.of(1L),
+                                                      "name");
+        Date created = DateUtil.parse("2026-05-14 10:11:12.345", DATE_FORMAT);
+        original.userdata(Userdata.CREATE_TIME, created);
+
+        BackendEntry entry = ser.writePropertyKey(original);
+        PropertyKey reloaded = ser.readPropertyKey(objects.graph(), entry);
+
+        Object value = reloaded.userdata().get(Userdata.CREATE_TIME);
+        Assert.assertTrue("CREATE_TIME should be a Date after round-trip, " +
+                          "was " + (value == null ? "null" : value.getClass()),
+                          value instanceof Date);
+        Assert.assertEquals(created, value);
+    }
+}