Import code from internal repository to git

java/com/google/domain/registry/model/common/CrossTldSingleton.java

@@ -0,0 +1,35 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// 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.
+
+package com.google.domain.registry.model.common;
+
+import static com.google.domain.registry.model.common.EntityGroupRoot.getCrossTldKey;
+
+import com.google.domain.registry.model.ImmutableObject;
+
+import com.googlecode.objectify.Key;
+import com.googlecode.objectify.annotation.Id;
+import com.googlecode.objectify.annotation.Parent;
+
+/** A singleton entity in the datastore. */
+public abstract class CrossTldSingleton extends ImmutableObject {
+
+  public static final long SINGLETON_ID = 1;  // There is always exactly one of these.
+
+  @Id
+  long id = SINGLETON_ID;
+
+  @Parent
+  Key<EntityGroupRoot> parent = getCrossTldKey();
+}