Book Image

Get Your Hands Dirty on Clean Architecture

By : Tom Hombergs
Book Image

Get Your Hands Dirty on Clean Architecture

By: Tom Hombergs

Overview of this book

Building for maintainability is key to keeping development costs low and processes easy. The second edition of Get Your Hands Dirty on Clean Architecture is here to equip you with the essential skills and knowledge to build maintainable software. With this comprehensive guide, you’ll explore the drawbacks of conventional layered architecture and the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, you’ll dive into hands-on explanations on how to convert hexagonal architecture into actual code. You'll learn in detail about different mapping strategies between the layers of hexagonal architecture and discover how to assemble the architectural elements into an application. Additionally, you’ll understand how to enforce architecture boundaries, which shortcuts produce what types of technical debt, and how, sometimes, it is a good idea to willingly take on those debts. By the end of this second edition, you'll be armed with a deep understanding of the hexagonal architecture style and be ready to create maintainable web applications that save money and time.
Table of Contents (13 chapters)

Implementing the Domain Model

We want to implement the use case of sending money from one account to another. One way to model this in object-oriented fashion is to create an Account entity that allows us to withdraw and deposit money so that we can withdraw money from the source account and deposit it into the target account:

package buckpal.domain;

public class Account {

  private AccountId id;

  private Money baselineBalance;

  private ActivityWindow activityWindow;

  // constructors and getters omitted

  public Money calculateBalance() {

    return Money.add(




  public boolean withdraw(Money, AccountId targetAccountId) {


    if (!mayWithdraw(money)) {