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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

WSDL: Just Another Object IDL

From the preceding section, you’d think that SOAP and HTTP are similar enough that the outbreak of WS-Peace would be imminent. After all, both define envelopes, both have an end-to-end processing model that includes intermediaries, and both rely on metadata. If there is complexity in the Web Services stack, it doesn’t come from SOAP.

But we don’t have to go far into the Web Services stack to find the source of most complexity: the Web Services Description Language, or WSDL. While WSDL pays lip service to SOAP’s message-oriented processing model, in fact it is mostly used as nothing more than a verbose object interface definition language (IDL), which forces an unsuitable RPC-like model of parameters, return values, and exceptions onto Web Services.

Center stage in WSDL 1.1 is the portType (the equivalent in WSDL 2.0 is the more honestly named interface), which is where all of the operations (!) that a Web Service supports are declared. Even to the casual observer, it’s clear how the WSDL in Example 11-4 maps directly onto the equivalent Java code in Example 11-5, or indeed how easy it would be to go from Java to the corresponding WSDL—both encouraging unhelpful tight coupling between the service’s contract and its implementation.

Example 11-4. Typical WSDL use

<wsdl:portType name="ordering"> <wsdl:operation name="placeOrder"> <wsdl:input message="restbucks:Order"/> <wsdl:output message="restbucks:OrderConfirmation"/> <wsdl:fault name="fault" message="restbucks:OrderException"/> ...

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