Mule in Action, Second Edition
David Dossot, John D’Emic, Victor Romero
(Manning – paperback)
An enterprise service bus (ESB) can help you link together many different types of platforms and applications–old and new–and keep them communicating and passing data between each other.
“Mule,” this book’s authors note, “is a lightweight, event-driven enterprise service bus and an integration platform and broker. As such, it resembles more a rich and diverse toolbox than a shrink-wrapped application.”
Mule in Action, Second Edition, is a comprehensive and generally well-written overview of Mule 3 and how to put its open-source building blocks together to create integration solutions and develop them with Mule. The book provides very good focus on sending, receiving, routing, and transforming data, key aspects of an ESB.
More attention, however, could have been paid to clarity and detail in Chapter 1, the all-important chapter that helps Mule newcomers get started and enthused.
This second edition is a recent update of the 2009 first edition. Unfortunately, the Mule screens have changed a bit since the book’s screen shots were created for the new edition. Therefore, some of the how-to instructions and screen images do not match what the user now sees. This gets particularly confusing while trying to learn how to configure a JMS outbound endpoint for the first time, using Mule Studio’s graphical editor. The instructions seem insufficient, and the mismatch of screens can leave a beginner unsure how to proceed.
The same goes for configuring the message setting in the Logger element. The text instructs: “You’ll set the message attribute to print a String followed by the payload of the message, using the Mule Expression Language.” But no example is given. Fortunately, a reviewer on Amazon has posted a correct procedure. In his view, the message attribute should be: We received a message: #[message.payload] –without any quote marks around it. (It works.)
Of course, this book is not really aimed at beginners–it’s for developers, architects, and managers (even though there will be Mule “beginners” in those ranks). Fortunately, it soon moves away from relying solely on Mule Studio’s graphical editor. The book’s examples, as the authors note, “mostly focus on the XML configurations of flows.” Thus, there are many XML code examples to work with, plus occasional screen shots of the flows as they appear in Mule Studio. And you can use other IDEs to work with the XML, if you prefer.
Indeed, the authors note, “no functionality in the CE version of Mule is dependent on Mule Studio.”
Overall, this is a very good book, and it definitely covers a lot of ground, from “discovering” Mule to becoming a Mule developer of integration applications, and using certain tools (such as business process management systems) to augment the applications you develop. I just wish a little more how-to clarity had been delivered in Chapter 1.
– Si Dunn