Merge branch '25-date-nano' into 'dev'

ID_COMPANION flag, DateNano type, @type annotation

See merge request objectbox/objectbox-java!54

Author: greenrobot-team

objectbox-java-api/src/main/java/io/objectbox/annotation/DatabaseType.java

@@ -0,0 +1,16 @@
+package io.objectbox.annotation;
+
+/**
+ * Use with {@link Type @Type} to override how a property value is stored and interpreted in the database.
+ */
+public enum DatabaseType {
+
+    /**
+     * Use with 64-bit long properties to store them as high precision time
+     * representing nanoseconds since 1970-01-01 (unix epoch).
+     * <p>
+     * By default, a 64-bit long value is interpreted as time in milliseconds (a Date).
+     */
+    DateNano
+
+}

objectbox-java-api/src/main/java/io/objectbox/annotation/Type.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2019 ObjectBox Ltd. 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 io.objectbox.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Use on a property to override how its value is stored and interpreted in the database.
+ * <p>
+ * For example to change a long to be interpreted as nanoseconds instead of milliseconds:
+ * <pre>
+ * &#064;Type(DatabaseType.DateNano)
+ * public long timeInNanos;
+ * </pre>
+ */
+@Retention(RetentionPolicy.CLASS)
+@Target({ElementType.FIELD})
+public @interface Type {
+
+    DatabaseType value();
+
+}