Professional Java EE Design Patterns

Murat Yener is an Android geek at Intel working on native and HTML5 mobile apps. He has extensive experience in Java, Web, Java EE and OSGi development. He is an Eclipse Committer, a speaker at major conferences, and a user group leader at GDG Istanbul. Alex Theedom is a senior developer at Indigo Code Collective (E-scape group) and has wide experience developing Java EE and Spring web applications. He has developed microservice-based architectures, ATM software, and e-learning systems in a diverse range of sectors throughout Europe. Wrox Professional guides are planned and written by working programmers to meet the real-world needs of programmers, developers, and IT professionals. Focused and relevant, they address the issues technology professionals face every day. They provide examples, practical solutions, and expert education in new technologies, all designed to help programmers do a better job.

FOREWORD xxiii INTRODUCTION xxv PART I: INTRODUCTION TO JAVA EE DESIGN PATTERNS CHAPTER 1: A BRIEF OVERVIEW OF DESIGN PATTERNS 3 What Is a Design Pattern? 4 How Patterns Were Discovered and Why We Need Them 5 Patterns in the Real World 5 Design Pattern Basics 6 Enterprise Patterns 7 Java to Enterprise Java 7 The Emergence of Enterprise Java Patterns 8 Design Patterns Versus Enterprise Patterns 8 Plain Old Design Patterns Meet Java EE 9 When Patterns Become Anti Patterns 10 Summary 10 Notes 10 CHAPTER 2: THE BASICS OF JAVA EE 13 Multitier Architecture 14 The Client Tier 15 The Middle Tier 16 Web Layer 16 Business Layer 16 The EIS Tier 18 Java EE Servers 18 The Java EE Web Profile 18 Core Principles of Java EE 19 Convention over Configuration 19 Context and Dependency Injection 20 Interceptors 21 Summary 22 Exercises 22 PART II: IMPLEMENTING DESIGN PATTERNS IN JAVA EE CHAPTER 3: FACADE PATTERN 25 What Is a Facade? 26 Facade Class Diagram 27 Implementing the Facade Pattern in Plain Code 27 Implementing the Facade Pattern in Java EE 29 Facade with Stateless Beans 29 Facade with Stateful Bean 31 Where and When to Use the Facade Pattern 31 Summary 31 Exercises 32 Notes 32 CHAPTER 4: SINGLETON PATTERN 33 What Is a Singleton? 34 Singleton Class Diagram 34 Implementing the Singleton Pattern in Plain Code 35 Implementing the Singleton Pattern in Java EE 38 Singleton Beans 39 Using Singletons at Startup 39 Determining Startup Order 40 Managing Concurrency 42 Where and When to Use the Singleton Pattern 45 Summary 46 Exercises 46 Notes 47 CHAPTER 5: DEPENDENCY INJECTION AND CDI 49 What Is Dependency Injection? 50 Implementing DI in Plain Code 50 Implementing DI in Java EE 53 The @Named Annotation 54 Context and Dependency Injection (CDI) 55 CDI Versus EJB 56 CDI Beans 56 The @Inject Annotation 57 Contexts and Scope 57 Naming and EL 58 CDI Beans for Backing JSF 58 Qualifi ers 59 Alternatives 59 Stereotypes 60 Other Patterns via CDI 60 Summary 61 Exercises 61 Notes 62 CHAPTER 6: FACTORY PATTERN 63 What Is a Factory? 64 Factory Method 64 Implementing the Factory Method in Plain Code 66 Abstract Factory 68 Implementing the Abstract Factory in Plain Code 69 Implementing the Factory Pattern in Java EE 70 Harness the Power of CDI 76 Where and When to Use the Factory Patterns 80 Summary 80 Exercises 81 Notes 81 CHAPTER 7: DECORATOR PATTERN 83 What Is a Decorator? 84 Decorator Class Diagram 85 Implementing the Decorator Pattern in Plain Code 86 Implementing the Decorator Pattern in Java EE 89 Decorators Without XML Confi guration 94 Where and When to Use the Decorator Pattern 94 Summary 95 Exercises 96 Notes 96 CHAPTER 8: ASPECT ORIENTED PROGRAMMING (INTERCEPTORS) 97 What Is Aspect Oriented Programming? 98 Implementing AOP in Plain Code 100 Aspects in Java EE, Interceptors 102 Interceptor Life Cycle 105 Default Level Interceptors 106 Interceptor Order 107 CDI Interceptors 109 Where and When to Use Interceptors 111 Summary 112 Notes 112 CHAPTER 9: ASYNCHRONOUS 113 What Is Asynchronous Programming? 114 Asynchronous Pattern 114 Implementing Asynchronous Pattern in Plain Code 116 Asynchronous Programming in Java EE 118 Asynchronous Beans 118 Asynchronous Servlets 120 Where and When to Use Asynchronous Programming 124 Summary 125 Exercises 125 Notes 126 CHAPTER 10: TIMER SERVICE 127 What Is the Timer Service? 127 Implementing a Timer in Java EE 130 Automatic Timers 130 Programmatic Timers 131 Timer Expression 134 Transactions 136 Summary 137 Exercises 137 Notes 138 CHAPTER 11: OBSERVER PATTERN 139 What Is an Observer? 139 Description 140 Observer Class Diagram 141 Implementing the Observer Pattern in Plain Code 142 Implementing the Observer Pattern in Java EE 144 Where and When to Use the Observer Pattern 149 Summary 150 Exercises 151 Notes 151 CHAPTER 12: DATA ACCESS PATTERN 153 What Is a Data Access Pattern? 154 Data Access Class Diagram 154 Overview of the Data Access Pattern 155 Data Transfer Object Pattern 155 Java Persistence Architecture API and Object Relational Mapping 156 Implementing the Data Access Pattern in Java EE 157 Type Safe DAO Implementation 162 Where and When to Use the Data Access Pattern 163 Summary 163 Exercises 163 Notes 163 CHAPTER 13: RESTFUL WEB SERVICES 165 What Is REST? 166 The Six Constraints of REST 167 Client Server 167 Uniform Interface 167 Stateless 168 Cacheable 168 Layered System 168 Code on Demand 168 Richardson Maturity Model of REST API 168 Level 0: The Swamp of POX (Plain Old XML) 169 Level 1: Resources 169 Level 2: HTTP Verbs 169 Level 3: Hypermedia Controls 169 Designing a RESTful API 169 Resource Naming 170 Nouns Not Verbs 170 Self Descriptive 170 Plural Not Singular 171 HTTP Methods 171 Get 171 Post 171 Put 172 Delete 172 Rest in Action 172 The users noun 172 The topics noun and the posts noun 173 Implementing REST in Java EE 175 HATEOAS 178 Where and When to Use REST 180 Summary 181 Exercises 181 Notes 182 CHAPTER 14: MODEL VIEW CONTROLLER PATTERN 183 What Is the MVC Design Pattern? 184 MVC Types 185 Implementing the MVC Pattern in Plain Code 186 Implementing the MVC Pattern in Java EE 190 The FacesServlet 190 MVC Using the FacesServlet 190 Where and When to Use the MVC Pattern 193 Summary 193 Exercises 193 Note 193 CHAPTER 15: OTHER PATTERNS IN JAVA EE 195 What Are WebSockets? 195 What Is Message Orientated Middleware 198 What Is the Microservice Architecture? 199 Monolithic Architecture 199 Scalability 200 Decomposing into Services 201 Microservice Benefi ts 202 Nothing in Life Is Free 203 Conclusions 204 Finally, Some Anti Patterns 204 Uber Class 204 Lasagna Architecture 204 Mr. Colombus 205 Friends with Benefi ts 205 Bleeding Edge 205 Utilityman 206 Notes 206 PART III: SUMMARY CHAPTER 16: DESIGN PATTERNS: THE GOOD,THE BAD, AND THE UGLY 209 The Good: Patterns for Success 209 The Bad: Over and Misuse of Patterns 211 and The Ugly 212 Summary 214 Notes 214 INDEX 215