Architecture of complex web applications
Architecture of complex web applications
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Architecture of complex web applications

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Completed on 2019-03-28

About the Book

I have worked with a lot of projects which was written by usual "everything in controller" way and when they become to grow their support complexity grows exponentially. Every project (simple internal app or app with 10 million unique visitors per day) had the same illnesses: Copy-paste driven development, God classes, etc. Modern frameworks offers a lot of features to implement functionality super-fast, but when project grows almost all these "optimizations" becomes a big pain for developers. In the same time there a lot of dogmas, like SOLID and others, which described very abstractly and becomes some kind of cargo cults. "if project has 100% code coverage by unit tests, it has super code quality", "if project doesn't have static methods, it's well organized", etc. Someone very clever said: Software Engineering Is Art Of Compromise. Some of these dogmas have very important exceptions. Some of them easy to misunderstand.

In this book I'm going to analyze usual project with common mistakes. How implementing new requirements can decrease code quality. Then step by step I'll show how I usually refactor the code: extracting classes, using DI, using exceptions. How this refactoring consequences moving to layered architecture. After moving to layered architecture we will talk about pro and contras of Command Query Responsibility Segregation(CQRS). After CQRS it's hard to don't talk about Event Sourcing(ES).

I'll use examples in Laravel , but it's not very important. The book is about framework-agnostic code.

About the Author

Adel F
Adel F

Software developer with 15+ years of experience. Contributed to Laravel plugin for PhpStorm. Created a .env files support plugin for PhpStorm.

Table of Contents

  • 1. Introduction
  • 2. Bad Habits
    • SRP violation
    • CRUD-style thinking
    • The worship of PHP dark magic
    • “Rapid” Application Development
    • Saving lines of code
    • Other sources of pain
  • 3. Dependency injection
    • Single responsibility principle
    • Dependency Injection
    • Inheritance
    • Image uploader example
    • Extending interfaces
    • Traits
    • Static methods
    • Conclusion
  • 4. Painless refactoring
    • “Static” typing
    • Templates
    • Model fields
  • 5. Application layer
    • Request data passing
    • Work with database
    • Service classes or command classes
  • 6. Error handling
    • Exceptions
    • Base exception class
    • Global handler
    • Checked and unchecked exceptions
    • Conclusion
  • 7. Validation
    • Database related validation
    • Two levels of validation
    • Validation by annotations
    • Value objects
    • VO as composition of values
    • Value object is not for user data validation
    • Conclusion
  • 8. Events
    • Database transactions
    • Queues
    • Events
    • Using Eloquent events
    • Entities as event fields
  • 9. Unit testing
    • First steps
    • Testing stateful classes
    • Testing classes with dependencies
    • Software testing types
    • Laravel testing
    • Application layer unit testing
    • Application testing strategy
  • 10. Domain layer
    • When and why?
    • Implementation of Domain layer
    • Error handling in domain layer
    • Conclusion
  • 11. CQRS
    • Reading and writing - different responsibilities?
    • Typical Application layer class
    • Command Query Responsibility Segregation
    • Conclusion
  • 12. Event sourcing
    • The kings game
    • Write model unit tests
    • World without magic
    • Implementing ES
    • Unique data in ES systems
    • Conclusion
  • 13. Sagas
    • Multi-system “transactions”
    • Orchestration
  • 14. Useful books and links
    • Classic
    • DDD
    • ES and CQRS
    • Unit testing

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