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REST in Practice

Cover of REST in Practice by Ian Robinson... Published by O'Reilly Media, Inc.
  1. REST in Practice
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. Foreword
    3. Preface
      1. Should I Read This Book?
      2. Should I Skip This Book?
      3. Resources
      4. What Did You Think About the Book?
      5. Errata
      6. Conventions Used in This Book
      7. Using Code Examples
      8. How to Contact Us
      9. Safari® Books Online
      10. Acknowledgments
    4. 1. The Web As a Platform for Building Distributed Systems
      1. Architecture of the Web
      2. Thinking in Resources
      3. From the Web Architecture to the REST Architectural Style
      4. The Web As an Application Platform
      5. Web Friendliness and the Richardson Maturity Model
      6. GET on Board
    5. 2. Introducing Restbucks: How to GET a Coffee, Web Style
      1. Restbucks: A Little Coffee Shop with Global Ambitions
      2. Toolbox
      3. Here Comes the Web
    6. 3. Basic Web Integration
      1. Lose Weight, Feel Great!
      2. A Simple Coffee Ordering System
      3. URI Templates
      4. URI Tunneling
      5. POX: Plain Old XML over HTTP
      6. We Are Just Getting Started
    7. 4. CRUD Web Services
      1. Modeling Orders As Resources
      2. Building CRUD Services
      3. Aligning Resource State
      4. Consuming CRUD Services
      5. Consuming Services Automatically with WADL
      6. CRUD Is Good, but It’s Not Great
    8. 5. Hypermedia Services
      1. The Hypermedia Tenet
      2. Hypermedia Formats
      3. Contracts
      4. Hypermedia Protocols
      5. Implementing a Hypermedia Service
      6. Building the Ordering Service in Java
      7. Building the Ordering Service in .NET
      8. Ready, Set, Action
    9. 6. Scaling Out
      1. GET Back to Basics
      2. Caching
      3. Making Content Cacheable
      4. Implementing Caching in .NET
      5. Consistency
      6. Extending Freshness
      7. Stay Fresh
    10. 7. The Atom Syndication Format
      1. The Format
      2. Common Uses for Atom
      3. Using Atom for Event-Driven Systems
      4. Building an Atom Service in Java
      5. Building an Atom Service in .NET
      6. Atom Everywhere?
      7. After the Event
    11. 8. Atom Publishing Protocol
      1. Atom Publishing Protocol
      2. Implementing Order Fulfillment Using AtomPub
      3. Implementing AtomPub in .NET
      4. A Versatile Protocol
    12. 9. Web Security
      1. HTTP Security Essentials
      2. Identity and the OpenID Protocol
      3. The OAuth Protocol
      4. Service Hacks and Defenses
      5. Final Thoughts
    13. 10. Semantics
      1. Syntax Versus Semantics
      2. Structure and Representation of Information
      3. The Semantic Web
      4. Microformats
      5. Linked Data and the Web
      6. Guidance
    14. 11. The Web and WS-*
      1. Are Web Services Evil?
      2. SOAP: The Whole Truth
      3. WSDL: Just Another Object IDL
      4. Two Wrongs Don’t Make a Right
      5. Secure, Reliable, Transacted
      6. A Requiem for Web Services?
    15. 12. Building the Case for the Web
      1. No More Silver Bullets
      2. Building and Running Web-Based Services
      3. No Architecture Without Measurement
      4. Selling the Web
      5. Go Forth and Build
    16. Index
    17. About the Authors
    18. Colophon
    19. SPECIAL OFFER: Upgrade this ebook with O’Reilly

From the Web Architecture to the REST Architectural Style

Intrigued by the Web, researchers studied its rapid growth and sought to understand the reasons for its success. In that spirit, the Web’s architectural underpinnings were investigated in a seminal work that supports much of our thinking around contemporary web-based systems.

As part of his doctoral work, Roy Fielding generalized the Web’s architectural principles and presented them as a framework of constraints, or an architectural style. Through this framework, Fielding described how distributed information systems such as the Web are built and operated. He described the interplay between resources, and the role of unique identifiers in such systems. He also talked about using a limited set of operations with uniform semantics to build a ubiquitous infrastructure that can support any type of application.[5] Fielding referred to this architectural style as REpresentational State Transfer, or REST. REST describes the Web as a distributed hypermedia application whose linked resources communicate by exchanging representations of resource state.


The description of the Web, as captured in W3C’s “Architecture of the World Wide Web”[6] and other IETF RFC[7] documents, was heavily influenced by Fielding’s work. The architectural abstractions and constraints he established led to the introduction of hypermedia as the engine of application state. The latter has given us a new perspective on how the Web can be used for tasks other than information storage and retrieval. His work on REST demonstrated that the Web is an application platform, with the REST architectural style providing guiding principles for building distributed applications that scale well, exhibit loose coupling, and compose functionality across service boundaries.

The idea is simple, and yet very powerful. A distributed application makes forward progress by transitioning from one state to another, just like a state machine. The difference from traditional state machines, however, is that the possible states and the transitions between them are not known in advance. Instead, as the application reaches a new state, the next possible transitions are discovered. It’s like a treasure hunt.


We’re used to this notion on the human Web. In a typical e-commerce solution such as, the server generates web pages with links on them that corral the user through the process of selecting goods, purchasing, and arranging delivery.

This is hypermedia at work, but it doesn’t have to be restricted to humans; computers are just as good at following protocols defined by state machines.

In a hypermedia system, application states are communicated through representations of uniquely identifiable resources. The identifiers of the states to which the application can transition are embedded in the representation of the current state in the form of links. Figure 1-7 illustrates such a hypermedia state machine.

Example of hypermedia as the engine for application state in action

Figure 1-7. Example of hypermedia as the engine for application state in action

This, in simple terms, is what the famous hypermedia as the engine of application state or HATEOAS constraint is all about. We see it in action every day on the Web, when we follow the links to other pages within our browsers. In this book, we show how the same principles can be used to enable computer-to-computer interactions.

REST and the Rest of This Book

While REST captures the fundamental principles that underlie the Web, there are still occasions where practice sidesteps theoretical guidance. Even so, the term REST has become so popular that it is almost impossible to disassociate it from any approach that uses HTTP.[8] It’s no surprise that the term REST is treated as a buzzword these days rather than as an accurate description of the Web’s blueprints.

The pervasiveness of HTTP sets it aside as being special among all the Internet protocols. The Web has become a universal “on ramp,” providing near-ubiquitous connectivity for billions of software agents across the planet. Correspondingly, the focus of this book is on the Web as it is used in practice—as a distributed application platform rather than as a single large hypermedia system. Although we are highly appreciative of Fielding’s research, and of much subsequent work in understanding web-scale systems, we’ll use the term web throughout this book to depict a warts-’n-all view, reserving the REST terminology to describe solutions that embrace the REST architectural style. We do this because many of today’s distributed applications on the Web do not follow the REST architectural tenets, even though many still refer to these applications as “RESTful.”

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