Learning Domain-Driven Design (ebook) Piekary Śląskie

Building software is harder than ever. As a developer, you not only have to chase ever-changing technological trends but also need to understand the business domains behind the software. This practical book provides you with a set of core patterns, principles, and practices for analyzing business domains, understanding business strategy, and, most importantly, aligning software design with its business needs.Author Vlad Khononov shows you how these practices lead to robust implementation of business logic and help to future-proof software design and architecture. You'll examine the relationship between domain-driven design (DDD) and other methodologies to ensure you make architectural decisions that meet business requirements. You'll also explore the real-life story of implementing DDD in a startup company.With this book, you'll learn how to:Analyze a company's business domain to learn how the system you're building fits its competitive strategyUse DDD's strategic and tactical tools to architect effective software solutions that address business needsBuild a shared understanding of the business domains you encounterDecompose a system into bounded contextsCoordinate the work of multiple teamsGradually introduce DDD to brownfield projects Spis treści: Foreword Preface Why I Wrote This Book Who Should Read This Book Navigating the Book Example Domain: WolfDesk Conventions Used in This Book Using Code Examples OReilly Online Learning How to Contact Us Acknowledgments Introduction I. Strategic Design 1. Analyzing Business Domains What Is a Business Domain? What Is a Subdomain? Types of Subdomains Core subdomains Complexity Sources of competitive advantage Generic subdomains Supporting subdomains Comparing Subdomains Competitive advantage Complexity Volatility Solution strategy Identifying Subdomain Boundaries Distilling subdomains Subdomains as coherent use cases Focus on the essentials Domain Analysis Examples Gigmaster Business domain and subdomains Core subdomains Generic subdomains Supporting subdomains Design decisions BusVNext Business domain and subdomains Core subdomains Generic subdomains Supporting subdomains Design decisions Who Are the Domain Experts? Conclusion Exercises 2. Discovering Domain Knowledge Business Problems Knowledge Discovery Communication What Is a Ubiquitous Language? Language of the Business Scenarios Consistency Ambiguous terms Synonymous terms Model of the Business Domain What Is a Model? Effective Modeling Modeling the Business Domain Continuous Effort Tools Challenges Conclusion Exercises 3. Managing Domain Complexity Inconsistent Models What Is a Bounded Context? Model Boundaries Ubiquitous Language Refined Scope of a Bounded Context Bounded Contexts Versus Subdomains Subdomains Bounded Contexts The Interplay Between Subdomains and Bounded Contexts Boundaries Physical Boundaries Ownership Boundaries Bounded Contexts in Real Life Semantic Domains Science Buying a Refrigerator Conclusion Exercises 4. Integrating Bounded Contexts Cooperation Partnership Shared Kernel Shared scope Implementation When to use shared kernel CustomerSupplier Conformist Anticorruption Layer Open-Host Service Separate Ways Communication Issues Generic Subdomains Model Differences Context Map Maintenance Limitations Conclusion Exercises II. Tactical Design 5. Implementing Simple Business Logic Transaction Script Implementation Its Not That Easy! Lack of transactional behavior Distributed transactions Implicit distributed transactions When to Use Transaction Script Active Record Implementation When to Use Active Record Be Pragmatic Conclusion Exercises 6. Tackling Complex Business Logic History Domain Model Implementation Complexity Ubiquitous language Building Blocks Value object Ubiquitous language Implementation When to use value objects Entities Aggregates Consistency enforcement Transaction boundary Hierarchy of entities Referencing other aggregates The aggregate root Domain events Ubiquitous language Domain services Managing Complexity Conclusion Exercises 7. Modeling the Dimension of Time Event Sourcing Search Analysis Source of Truth Event Store Event-Sourced Domain Model Advantages Disadvantages Frequently Asked Questions Performance Deleting Data Why Cant I Just? Conclusion Exercises 8. Architectural Patterns Business Logic Versus Architectural Patterns Layered Architecture Presentation Layer Business Logic Layer Data Access Layer Communication Between Layers Variation Service layer Terminology When to Use Layered Architecture Ports & Adapters Terminology Dependency Inversion Principle Integration of Infrastructural Components Variants When to Use Ports & Adapters Command-Query Responsibility Segregation Polyglot Modeling Implementation Command execution model Read models (projections) Projecting Read Models Synchronous projections Asynchronous projections Challenges Model Segregation When to Use CQRS Scope Conclusion Exercises 9. Communication Patterns Model Translation Stateless Model Translation Synchronous Asynchronous Stateful Model Translation Aggregating incoming data Unifying multiple sources Integrating Aggregates Outbox Fetching unpublished events Saga Consistency Process Manager Conclusion Exercises III. Applying Domain-Driven Design in Practice 10. Design Heuristics Heuristic Bounded Contexts Business Logic Implementation Patterns Architectural Patterns Testing Strategy Testing Pyramid Testing Diamond Reversed Testing Pyramid Tactical Design Decision Tree Conclusion Exercises 11. Evolving Design Decisions Changes in Domains Core to Generic Generic to Core Supporting to Generic Supporting to Core Core to Supporting Generic to Supporting Strategic Design Concerns Tactical Design Concerns Transaction Script to Active Record Active Record to Domain Model Domain Model to Event-Sourced Domain Model Generating Past Transitions Modeling Migration Events Organizational Changes Partnership to CustomerSupplier CustomerSupplier to Separate Ways Domain Knowledge Growth Subdomains Bounded Contexts Aggregates Conclusion Exercises 12. EventStorming What Is EventStorming? Who Should Participate in EventStorming? What Do You Need for EventStorming? The EventStorming Process Step 1: Unstructured Exploration Step 2: Timelines Step 3: Pain Points Step 4: Pivotal Events Step 5: Commands Step 6: Policies Step 7: Read Models Step 8: External Systems Step 9: Aggregates Step 10: Bounded Contexts Variants When to Use EventStorming Facilitation Tips Watch the Dynamics Remote EventStorming Conclusion Exercises 13. Domain-Driven Design in the Real World Strategic Analysis Understand the Business Domain Core subdomains Generic subdomains Supporting subdomains Explore the Current Design Evaluate the tactical design Evaluate the strategic design Modernization Strategy Strategic Modernization Tactical Modernization Cultivate a Ubiquitous Language Strangler pattern Refactoring tactical design decisions Pragmatic Domain-Driven Design Selling Domain-Driven Design Undercover Domain-Driven Design Ubiquitous language Bounded contexts Tactical design decisions Event-sourced domain model Conclusion Exercises IV. Relationships to Other Methodologies and Patterns 14. Microservices What Is a Service? What Is a Microservice? Method as a Service: Perfect Microservices? Design Goal System Complexity Microservices as Deep Services Microservices as Deep Modules Domain-Driven Design and Microservices Boundaries Bounded Contexts Aggregates Subdomains Compressing Microservices Public Interfaces Open-Host Service Anticorruption Layer Conclusion Exercises 15. Event-Driven Architecture Event-Driven Architecture Events Events, Commands, and Messages Structure Types of Events Event notification Security Concurrency Event-carried state transfer Domain event Domain events versus event notification Domain events versus event-carried state transfer Event types: Example Designing Event-Driven Integration Distributed Big Ball of Mud Temporal Coupling Functional Coupling Implementation Coupling Refactoring the Event-Driven Integration Event-Driven Design Heuristics Assume the worst Use public and private events Evaluate consistency requirements Conclusion Exercises 16. Data Mesh Analytical Data Model Versus Transactional Data Model Fact Table Dimension Table Analytical Models Analytical Data Management Platforms Data Warehouse Data Lake Challenges of Data Warehouse and Data Lake Architectures Data Mesh Decompose Data Around Domains Data as a Product Enable Autonomy Build an Ecosystem Combining Data Mesh and Domain-Driven Design Conclusion Exercises Closing Words Problem Solution Implementation Further Reading Advanced Domain-Driven Design Architectural and Integration Patterns Modernization of Legacy Systems EventStorming Conclusion A. Applying DDD: A Case Study Five Bounded Contexts Business Domain Bounded Context #1: Marketing A kind of magic Our early understanding of domain-driven design Bounded Context #2: CRM More aggregates! Solution design: Take two Tower of Babel 2.0 A broader understanding of domain-driven design Bounded Context #3: Event Crunchers Bounded Context #4: Bonuses Design: Take two Ubiquitous language A classic understanding of domain-driven design Bounded Context #5: The Marketing Hub Micro what? The real problem Discussion Ubiquitous Language Subdomains Mapping design decisions to subdomains Dont ignore pain Boundaries of Bounded Contexts Conclusion B. Answers to Exercise Questions Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 References Index