The Book
Title: REST in Practice (Hypermedia and Systems Architecture)
Authors: Jim Webber, Savas Parastatidis, Ian Robinson
Publisher: O’Reilly Media
Review
Couple of years ago, the authors of this book penned one of the finest articles explaining the principles of REST titled How to GET a Cup of Coffee. I was so thrilled when I first heard that the same authors are expanding the concepts into a book form! Now that the book is out and I finished reading it, here are some of my thoughts …
This book covers a wide spectrum of ideas related to the RESTful systems including RPC-style systems, CRUD-based services, hypermedia systems, caching, Atom syndication and publishing protocol, security, and semantic web. The key is too see HTTP as an application-level protocol and not as a transport protocol. Start with that basic understanding, each chapter in the book deal with various integration challenges in the enterprise. Heart of this book is the focus towards building the systems in a web-centric way.
As the concepts evolve from chapter to chapter they are evaluated against the Richardson’s maturity model. At the base of the Richardson’s model are the systems that use RPC-style (HTTP-as-transport-protocol) systems. The next level up, Level 1, are the systems that work in a resource-oriented model. Endpoints give way to thinking in terms of resources and URIs (e.g: OrderRequest end-point where a particular function on order is invoked vs. Order as a resource, example.org/order/1234).
Going up the pyramid, Level 2 maturity is attained by conforming to a uniform interface (HTTP verbs) and well-known HTTP response codes. There are many systems that claim to be RESTful but don’t go beyond Level 2 (I don’t want to sound pedantic, but just pointing out!). There are other articles and books with good details about Level 1 and Level 2 systems. If there is one take away from this book I have to say it’s the understanding of the Level 3 of the maturity model, hypermedia systems. HATEOAS (Hypermedia as the Engine of the Application State) principle has been often discussed in various forums but perhaps not that well understood.
As with their InfoQ article, Restbucks, a coffee store web-application, is being built as the discussion proceeds from simple concepts to the more advanced ones. A domain that almost everyone can identify with, and puts the focus on the technical discussion rather than on the domain model intricacies. REST in practice, as the name suggests, takes the approach of implementing the concepts as they are discussed; Java and .NET are used in the book. Reading code is some times easier than understanding the abstract concepts, if you are like me.
Discussion on Atom and Atom publishing protocol is one of the best. If you don’t have low latency (in micro seconds) requirement Atom format is the one that has to be given a good consideration while designing event-driven systems. In the penultimate chapter the authors compare Web services (SOAP and WS-* stack) with web-based (REST) systems. They compared both models in great length with respect to security, reliability, transaction management (including two-phase commits). A compelling read for anybody who is trying to get a hang of what these models offer.
Subbu Allamaraju’s RESTful Web Services Cookbook is one of my favorites on the topic. I was fortunate enough to read the book during it’s draft stage, which actually helped me immensely in understanding and reinforcing some of my concepts. This book, REST in practice, helped me further in understanding more advanced topics like semantic web (RDF, OWL), and the event-driven system integration. I thoroughly enjoyed the book, and would certainly recommend for all REST enthusiasts (and doubters).
