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Add AE Datastore transactions samples. (GoogleCloudPlatform#223)
From: https://cloud.google.com/appengine/docs/java/datastore/transactions
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‎appengine/datastore/src/test/java/com/example/appengine/TransactionsTest.java

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/*
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.appengine;
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import static com.google.common.truth.Truth.assertThat;
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import static org.junit.Assert.fail;
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import com.google.appengine.api.datastore.DatastoreService;
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import com.google.appengine.api.datastore.DatastoreServiceFactory;
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import com.google.appengine.api.datastore.Entity;
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import com.google.appengine.api.datastore.EntityNotFoundException;
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import com.google.appengine.api.datastore.FetchOptions;
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import com.google.appengine.api.datastore.Key;
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import com.google.appengine.api.datastore.KeyFactory;
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import com.google.appengine.api.datastore.PreparedQuery;
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import com.google.appengine.api.datastore.Query;
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import com.google.appengine.api.datastore.Transaction;
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import com.google.appengine.api.datastore.TransactionOptions;
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import com.google.appengine.api.taskqueue.Queue;
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import com.google.appengine.api.taskqueue.QueueFactory;
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import com.google.appengine.api.taskqueue.TaskOptions;
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import com.google.appengine.tools.development.testing.LocalDatastoreServiceTestConfig;
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import com.google.appengine.tools.development.testing.LocalServiceTestHelper;
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import org.junit.After;
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import org.junit.Before;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.junit.runners.JUnit4;
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import java.util.ConcurrentModificationException;
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import java.util.Date;
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import java.util.List;
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/**
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* Unit tests to demonstrate App Engine Datastore transactions.
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*/
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@RunWith(JUnit4.class)
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public class TransactionsTest {
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private final LocalServiceTestHelper helper =
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new LocalServiceTestHelper(
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// Use High Rep job policy to allow cross group transactions in tests.
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new LocalDatastoreServiceTestConfig().setApplyAllHighRepJobPolicy());
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private DatastoreService datastore;
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@Before
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public void setUp() {
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helper.setUp();
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datastore = DatastoreServiceFactory.getDatastoreService();
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}
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@After
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public void tearDown() {
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// Clean up any dangling transactions.
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Transaction txn = datastore.getCurrentTransaction(null);
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if (txn != null && txn.isActive()) {
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txn.rollback();
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}
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helper.tearDown();
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}
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@Test
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public void usingTransactions() throws Exception {
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Entity joe = new Entity("Employee", "Joe");
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datastore.put(joe);
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// [START using_transactions]
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DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
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Transaction txn = datastore.beginTransaction();
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try {
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Key employeeKey = KeyFactory.createKey("Employee", "Joe");
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Entity employee = datastore.get(employeeKey);
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employee.setProperty("vacationDays", 10);
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datastore.put(txn, employee);
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txn.commit();
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} finally {
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if (txn.isActive()) {
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txn.rollback();
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}
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}
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// [END using_transactions]
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}
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@Test
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public void entityGroups() throws Exception {
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try {
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// [START entity_groups]
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DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
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Entity person = new Entity("Person", "tom");
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datastore.put(person);
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// Transactions on root entities
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Transaction txn = datastore.beginTransaction();
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Entity tom = datastore.get(person.getKey());
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tom.setProperty("age", 40);
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datastore.put(txn, tom);
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txn.commit();
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// Transactions on child entities
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txn = datastore.beginTransaction();
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tom = datastore.get(person.getKey());
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Entity photo = new Entity("Photo", tom.getKey());
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// Create a Photo that is a child of the Person entity named "tom"
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photo.setProperty("photoUrl", "http://domain.com/path/to/photo.jpg");
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datastore.put(txn, photo);
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txn.commit();
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// Transactions on entities in different entity groups
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txn = datastore.beginTransaction();
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tom = datastore.get(person.getKey());
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Entity photoNotAChild = new Entity("Photo");
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photoNotAChild.setProperty("photoUrl", "http://domain.com/path/to/photo.jpg");
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datastore.put(txn, photoNotAChild);
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// Throws IllegalArgumentException because the Person entity
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// and the Photo entity belong to different entity groups.
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txn.commit();
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// [END entity_groups]
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fail("Expected IllegalArgumentException");
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} catch (IllegalArgumentException expected) {
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// We expect to get an exception that complains that we don't have a XG-transaction.
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}
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}
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@Test
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public void creatingAnEntityInASpecificEntityGroup() throws Exception {
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String boardName = "my-message-board";
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// [START creating_an_entity_in_a_specific_entity_group]
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DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
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String messageTitle = "Some Title";
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String messageText = "Some message.";
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Date postDate = new Date();
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Transaction txn = datastore.beginTransaction();
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Key messageBoardKey = KeyFactory.createKey("MessageBoard", boardName);
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Entity message = new Entity("Message", messageBoardKey);
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message.setProperty("message_title", messageTitle);
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message.setProperty("message_text", messageText);
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message.setProperty("post_date", postDate);
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datastore.put(txn, message);
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txn.commit();
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// [END creating_an_entity_in_a_specific_entity_group]
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}
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@Test
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public void crossGroupTransactions() throws Exception {
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// [START cross-group_XG_transactions_using_the_Java_low-level_API]
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DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
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TransactionOptions options = TransactionOptions.Builder.withXG(true);
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Transaction txn = datastore.beginTransaction(options);
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Entity a = new Entity("A");
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a.setProperty("a", 22);
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datastore.put(txn, a);
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Entity b = new Entity("B");
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b.setProperty("b", 11);
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datastore.put(txn, b);
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txn.commit();
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// [END cross-group_XG_transactions_using_the_Java_low-level_API]
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}
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@Test
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public void usesForTransactions_relativeUpdates() throws Exception {
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String boardName = "my-message-board";
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Entity b = new Entity("MessageBoard", boardName);
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b.setProperty("count", 41);
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datastore.put(b);
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// [START uses_for_transactions_1]
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int retries = 3;
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while (true) {
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Transaction txn = datastore.beginTransaction();
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try {
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Key boardKey = KeyFactory.createKey("MessageBoard", boardName);
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Entity messageBoard = datastore.get(boardKey);
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long count = (Long) messageBoard.getProperty("count");
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++count;
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messageBoard.setProperty("count", count);
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datastore.put(txn, messageBoard);
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txn.commit();
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break;
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} catch (ConcurrentModificationException e) {
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if (retries == 0) {
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throw e;
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}
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// Allow retry to occur
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--retries;
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} finally {
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if (txn.isActive()) {
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txn.rollback();
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}
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}
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}
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// [END uses_for_transactions_1]
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b = datastore.get(KeyFactory.createKey("MessageBoard", boardName));
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assertThat((long) b.getProperty("count")).named("board.count").isEqualTo(42L);
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}
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private Entity fetchOrCreate(String boardName) {
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// [START uses_for_transactions_2]
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Transaction txn = datastore.beginTransaction();
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Entity messageBoard;
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Key boardKey;
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try {
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boardKey = KeyFactory.createKey("MessageBoard", boardName);
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messageBoard = datastore.get(boardKey);
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} catch (EntityNotFoundException e) {
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messageBoard = new Entity("MessageBoard", boardName);
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messageBoard.setProperty("count", 0L);
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boardKey = datastore.put(txn, messageBoard);
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}
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txn.commit();
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// [END uses_for_transactions_2]
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return messageBoard;
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}
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@Test
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public void usesForTransactions_fetchOrCreate_fetchesExisting() throws Exception {
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Entity b = new Entity("MessageBoard", "my-message-board");
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b.setProperty("count", 7);
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datastore.put(b);
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Entity board = fetchOrCreate("my-message-board");
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assertThat((long) board.getProperty("count")).named("board.count").isEqualTo(7L);
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}
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@Test
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public void usesForTransactions_fetchOrCreate_createsNew() throws Exception {
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Entity board = fetchOrCreate("my-message-board");
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assertThat((long) board.getProperty("count")).named("board.count").isEqualTo(0L);
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}
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@Test
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public void usesForTransactions_readSnapshot() throws Exception {
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String boardName = "my-message-board";
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Entity b = new Entity("MessageBoard", boardName);
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b.setProperty("count", 13);
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datastore.put(b);
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// [START uses_for_transactions_3]
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DatastoreService ds = DatastoreServiceFactory.getDatastoreService();
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// Display information about a message board and its first 10 messages.
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Key boardKey = KeyFactory.createKey("MessageBoard", boardName);
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Transaction txn = datastore.beginTransaction();
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Entity messageBoard = datastore.get(boardKey);
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long count = (Long) messageBoard.getProperty("count");
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Query q = new Query("Message", boardKey);
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// This is an ancestor query.
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PreparedQuery pq = datastore.prepare(txn, q);
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List<Entity> messages = pq.asList(FetchOptions.Builder.withLimit(10));
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txn.commit();
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// [END uses_for_transactions_3]
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assertThat(count).named("board.count").isEqualTo(13L);
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}
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@Test
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public void transactionalTaskEnqueuing() throws Exception {
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// [START transactional_task_enqueuing]
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DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
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Queue queue = QueueFactory.getDefaultQueue();
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Transaction txn = datastore.beginTransaction();
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// ...
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queue.add(TaskOptions.Builder.withUrl("/path/to/handler"));
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// ...
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txn.commit();
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// [END transactional_task_enqueuing]
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}
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}

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