Programming Google App Engine with Java: Build and Run Scalable Java Applications on Google's Infrastructure

This practical guide shows intermediate and advanced web and mobile app developers how to build highly scalable Java applications in the cloud with Google App Engine. The flagship of Google's Cloud Platform, App Engine hosts your app on infrastructure that grows automatically with your traffic, minimizing up-front costs and accommodating unexpected visitors. You’ll learn hands-on how to perform common development tasks with App Engine services and development tools, including deployment and maintenance. For Java applications, App Engine provides a J2EE standard servlet container with a complete Java 7 JVM and standard library. Because App Engine supports common Java API standards, your code stays clean and portable. * Get a hands-on introduction to App Engine's tools and features, using an example application * Simulate App Engine on your development machine directly from Eclipse * Structure your app into individually addressable modules, each with its own scaling configuration * Exploit the power of the scalable Cloud Datastore, using queries, transactions, and data modeling with JPA * Use Cloud SQL for standard relational databases with App Engine applications * Learn how to deploy, manage, and inspect your application on Google infrastructure Copyright 4 Table of Contents 5 Preface 13 A Brief History of App Engine 15 Using This Book 16 Conventions Used in This Book 20 Safari庐 Books Online 21 How to Contact Us 21 Acknowledgments 22 Chapter 1. Introducing Google App Engine 25 The Runtime Environment 26 The Static File Servers 28 Frontend Caches 29 Cloud Datastore 29 Entities and Properties 30 Queries and Indexes 31 Transactions 32 The Services 33 Google Accounts, OpenID, and OAuth 35 Google Cloud Endpoints 36 Task Queues and Cron Jobs 36 Namespaces 38 Developer Tools 38 The Cloud Console 39 Getting Started 40 Chapter 2. Creating an Application 41 Setting Up the Cloud SDK 41 Installing Java 42 Installing Python 43 Installing the Cloud SDK 43 Authenticating with the Cloud SDK 44 Installing the App Engine SDK 45 Installing the Java SDK with the Google Plugin for Eclipse 46 Developing the Application 49 The User Preferences Pattern 49 A Simple App 50 Introducing JSPs, JSTL, and EL 56 Users and Google Accounts 61 Web Forms and the Datastore 63 Caching with Memcache 68 The Development Console 71 Registering the Application 72 Uploading the Application 72 Testing the App 74 Enabling Billing 75 Chapter 3. Configuring an Application 77 The App Engine Architecture 78 Configuring a Java App 80 App IDs and Versions 82 Multithreading 84 Request Handlers 84 Static Files and Resource Files 86 Domain Names 89 Google Apps 91 Configuring Secure Connections 94 Secure Connections with Custom Domains 96 Authorization with Google Accounts 98 Environment Variables 100 Inbound Services 100 Custom Error Responses 101 Java Servlet Sessions 102 Chapter 4. Request Handlers and Instances 105 The Runtime Environment 106 The Sandbox 107 Quotas and Limits 108 The Java Runtime Environment 113 The Request Handler Abstraction 114 Introducing Instances 117 Request Scheduling and Pending Latency 120 Warmup Requests 121 Resident Instances 122 Instance Classes and Utilization 123 Instance Hours and Billing 124 The Instances Console Panel 125 Traffic Splitting 126 Chapter 5. Using Modules 129 An Example Layout 130 Configuring Modules 131 The Enterprise Archive Layout 132 Making Modules with Eclipse 134 Manual and Basic Scaling 137 Manual Scaling and Versions 139 Startup Requests 139 Shutdown Hooks 140 Background Threads 141 Modules and the Development Server 142 Deploying Modules 143 Addressing Modules with URLs 144 Calling Modules from Other Modules 145 Module URLs and Secure Connections 147 Module URLs and Custom Domains 147 Dispatching Requests to Modules 148 Starting and Stopping Modules 149 Managing and Deleting Modules and Versions 150 The Modules API 151 An Always-On Example 152 Chapter 6. Datastore Entities 157 Entities, Keys, and Properties 158 Introducing the Java Datastore API 160 Property Values 163 Strings, Text, and Bytes 164 Unset Versus the Null Value 166 Multivalued Properties 166 Keys and Key Objects 167 Using Entities 169 Getting Entities Using Keys 169 Saving Entities 170 Deleting Entities 171 Allocating System IDs 172 The Development Server and the Datastore 173 Chapter 7. Datastore Queries 175 Queries and Kinds 176 Query Results and Keys 177 The Query API 177 Building the Query 179 Fetching Results with PreparedQuery 181 Keys-Only Queries 182 Introducing Indexes 183 Automatic Indexes and Simple Queries 185 All Entities of a Kind 186 One Equality Filter 186 Greater-Than and Less-Than Filters 187 One Sort Order 188 Queries on Keys 190 Kindless Queries 191 Custom Indexes and Complex Queries 192 Multiple Sort Orders 192 Filters on Multiple Properties 193 Multiple Equality Filters 196 Not-Equal and IN Filters 199 Unset and Nonindexed Properties 200 Sort Orders and Value Types 201 Queries and Multivalued Properties 202 MVPs in Code 202 MVPs and Equality Filters 204 MVPs and Inequality Filters 206 MVPs and Sort Orders 208 Exploding Indexes 210 Query Cursors 210 Projection Queries 214 Configuring Indexes 217 Chapter 8. Datastore Transactions 221 Entities and Entity Groups 223 Keys, Paths, and Ancestors 225 Ancestor Queries 226 What Can Happen in a Transaction 228 Transactional Reads 228 Eventually Consistent Reads 229 Transactions in Java 230 How Entities Are Updated 234 How Entities Are Read 237 Batch Updates 237 How Indexes Are Updated 238 Cross-Group Transactions 240 Chapter 9. Datastore Administration 243 Inspecting the Datastore 243 Managing Indexes 245 Accessing Metadata from the App 247 Querying Statistics 248 Querying Metadata 250 Index Status and Queries 251 Entity Group Versions 252 Remote Controls 253 Setting Up the Remote API 253 Using the Remote API with the Java Client Library 254 Chapter 10. The Java Persistence API 257 Setting Up JPA 258 Entities and Keys 259 Entity Properties 262 Embedded Objects 264 Saving, Fetching, and Deleting Objects 264 Transactions in JPA 266 Queries and JPQL 268 Relationships 271 For More Information 276 Chapter 11. Using Google Cloud SQL with App Engine 277 Choosing a Cloud SQL Instance 278 Installing MySQL Locally 279 Creating a Cloud SQL Instance 280 Connecting to an Instance from Your Computer 282 Setting Up a Database 284 Setting Up JDBC 286 Connecting to the Database from App Engine 287 Backup and Restore 294 Exporting and Importing Data 294 The gcloud sql Commands 295 Chapter 12. The Memory Cache 299 Calling Memcache from Java 301 Keys and Values 302 Setting Values 302 Setting Values That Expire 302 Adding and Replacing Values 303 Getting Values 304 Deleting Values 304 Locking a Deleted Key 304 Atomic Increment and Decrement 305 Compare and Set 306 Batching Calls to Memcache 307 Memcache and the Datastore 308 Handling Memcache Errors 309 Memcache Administration 309 Cache Statistics 310 Flushing the Memcache 311 Chapter 13. Fetching URLs and Web Resources 313 Fetching URLs 315 Outgoing HTTP Requests 317 The URL 318 The HTTP Method and Payload 318 Request Headers 319 HTTP over SSL (HTTPS) 319 Request and Response Sizes 320 Request Deadlines 320 Handling Redirects 321 Response Objects 321 Chapter 14. Sending and Receiving Email Messages 323 Sending Email Messages 325 Logging Sent Mail in the Development Server 326 Sender Addresses 326 Recipients 328 Attachments 328 Sending Email 329 Receiving Email Messages 332 Chapter 15. Sending and Receiving Instant Messages with XMPP 335 Inviting a User to Chat 336 Sending Chat Messages 338 Receiving Chat Messages 340 Receiving Chat Messages in Java 341 Handling Error Messages 342 Managing Presence 343 Managing Subscriptions 344 Managing Presence Updates 346 Probing for Presence 350 Chapter 16. Task Queues and Scheduled Tasks 353 Configuring Task Queues 356 Enqueuing a Task 357 Task Parameters 359 Payloads 359 Task Names 360 Countdowns and ETAs 362 Push Queues 362 Task Requests 363 Processing Rates and Token Buckets 364 Retrying Push Tasks 366 Pull Queues 368 Enqueuing Tasks to Pull Queues 369 Leasing and Deleting Tasks 369 Retrying Pull Queue Tasks 370 Transactional Task Enqueueing 371 Task Chaining 374 Task Queue Administration 379 Deferring Work 380 Scheduled Tasks 381 Configuring Scheduled Tasks 382 Specifying Schedules 383 Chapter 17. Optimizing Service Calls 385 Calling Services Asynchronously 386 The Asynchronous Call API 389 Visualizing Calls with AppStats 391 Installing AppStats 393 Using the AppStats Console 394 Chapter 18. Managing Request Logs 399 Writing to the Log 400 Viewing Recent Logs 402 Downloading Logs 404 Logs Retention 405 Querying Logs from the App 406 Chapter 19. Deploying and Managing Applications 409 Uploading an Application 410 Using Versions 410 Managing Service Configuration 413 App Engine Settings 413 Managing Developers 414 Quotas and Billing 415 Getting Help 416 Index 419 About the Author 431 This practical guide shows intermediate and advanced web and mobile app developers how to build highly scalable Java applications in the cloud with Google App Engine. The flagship of Google's Cloud Platform, App Engine hosts your app on infrastructure that grows automatically with your traffic, minimizing up-front costs and accommodating unexpected visitors. You{u2019}ll learn hands-on how to perform common development tasks with App Engine services and development tools, including deployment and maintenance. For Java applications, App Engine provides a J2EE standard servlet container with a complete Java 7 JVM and standard library. Because App Engine supports common Java API standards, your code stays clean and portable. Get a hands-on introduction to App Engine's tools and features, using an example application Simulate App Engine on your development machine directly from Eclipse Structure your app into individually addressable modules, each with its own scaling configuration Exploit the power of the scalable Cloud Datastore, using queries, transactions, and data modeling with JPA Use Cloud SQL for standard relational databases with App Engine applications Learn how to deploy, manage, and inspect your application on Google infrastructure