samples: Add example snippet for snapshot reads (#809)

* Add sample snippet for snapshot reads * Fix linting error * Change readtime to 15 seconds ago. Incorporate feedback.

Author: jlara310

samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java

@@ -1145,4 +1145,31 @@ public void testInQuerySorted() {
  // [END datastore_in_query_sorted]
  assertValidQueryRealBackend(query);
  }
+
+ @Test
+ public void testStaleReads() {
+ setUpQueryTestsRealBackend();
+ Datastore datastoreClient = datastoreRealBackend;
+ // [START datastore_stale_read]
+ Key taskKey =
+ datastoreClient
+ .newKeyFactory()
+ .setKind("Task")
+ .addAncestors(PathElement.of("TaskList", "default"))
+ .newKey("someTask");
+
+ Timestamp fifteenSecondsAgo =
+ Timestamp.ofTimeSecondsAndNanos(Timestamp.now().getSeconds() - 15L, 0);
+ // Create a readOption with read time fifteenSecondsAgo
+ ReadOption readOption = ReadOption.readTime(fifteenSecondsAgo);
+ // Use the readOption to Fetch entity
+ Entity entity = datastoreClient.get(taskKey, readOption);
+
+ // Use the readOption to Query kind Task
+ Query<Entity> query = Query.newEntityQueryBuilder().setKind("Task").setLimit(10).build();
+ QueryResults<Entity> results = datastoreClient.run(query, readOption);
+ Entity result = results.next();
+ // [END datastore_stale_read]
+ assertValidQueryRealBackend(query);
+ }
 }