Book Image

Domain-Driven Design with Java - A Practitioner's Guide

By : Premanand Chandrasekaran, Karthik Krishnan
Book Image

Domain-Driven Design with Java - A Practitioner's Guide

By: Premanand Chandrasekaran, Karthik Krishnan

Overview of this book

Domain-Driven Design (DDD) makes available a set of techniques and patterns that enable domain experts, architects, and developers to work together to decompose complex business problems into a set of well-factored, collaborating, and loosely coupled subsystems. This practical guide will help you as a developer and architect to put your knowledge to work in order to create elegant software designs that are enjoyable to work with and easy to reason about. You'll begin with an introduction to the concepts of domain-driven design and discover various ways to apply them in real-world scenarios. You'll also appreciate how DDD is extremely relevant when creating cloud native solutions that employ modern techniques such as event-driven microservices and fine-grained architectures. As you advance through the chapters, you'll get acquainted with core DDD’s strategic design concepts such as the ubiquitous language, context maps, bounded contexts, and tactical design elements like aggregates and domain models and events. You'll understand how to apply modern, lightweight modeling techniques such as business value canvas, Wardley mapping, domain storytelling, and event storming, while also learning how to test-drive the system to create solutions that exhibit high degrees of internal quality. By the end of this software design book, you'll be able to architect, design, and implement robust, resilient, and performant distributed software solutions.
Table of Contents (17 chapters)
Part 1: Foundations
Part 2: Real-World DDD
Part 3: Evolution Patterns

Implementing sagas

Before we delve into how we can implement this auto-approval functionality, let’s take a look at how this works from a logical perspective, as shown here:

Figure 8.2 – Auto-approval process—logical view

As depicted in the preceding diagram, there are three bounded contexts in play:

  • LC Application (the bounded context we have been implementing thus far)
  • The Applicant bounded context
  • The Product bounded context

The flow gets triggered when the LC application is submitted. This in turn sets in motion three independent functions that establish the following:

  • Value of the product being transacted
  • Legality of the product being transacted
  • Creditworthiness of the applicant

LC approval can proceed only after all of these functions have been completed. Furthermore, to auto-approve, all of these checks have to complete favorably and, as mentioned earlier, the LC amount has to be less...