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Kotlin Design Patterns and Best Practices - Second Edition

You're reading from  Kotlin Design Patterns and Best Practices - Second Edition

Product type Book
Published in Jan 2022
Publisher Packt
ISBN-13 9781801815727
Pages 356 pages
Edition 2nd Edition
Languages
Author (1):
Alexey Soshin Alexey Soshin
Profile icon Alexey Soshin

Table of Contents (17) Chapters

Preface 1. Section 1: Classical Patterns
2. Chapter 1: Getting Started with Kotlin 3. Chapter 2: Working with Creational Patterns 4. Chapter 3: Understanding Structural Patterns 5. Chapter 4: Getting Familiar with Behavioral Patterns 6. Section 2: Reactive and Concurrent Patterns
7. Chapter 5: Introducing Functional Programming 8. Chapter 6: Threads and Coroutines 9. Chapter 7: Controlling the Data Flow 10. Chapter 8: Designing for Concurrency 11. Section 3: Practical Application of Design Patterns
12. Chapter 9: Idioms and Anti-Patterns 13. Chapter 10: Concurrent Microservices with Ktor 14. Chapter 11: Reactive Microservices with Vert.x 15. Assessments 16. Other Books You May Enjoy

Chain of Responsibility

I'm a horrible software architect, and I don't particularly appreciate speaking with people. Hence, while sitting in The Ivory Tower (that's the name of the cafe I often visit), I wrote a small web application. If a developer has a question, they shouldn't approach me directly, oh no! They'll need to send me a proper request through this system and I shall only answer them if I deem their request worthy.

A filter chain is a ubiquitous concept in web servers. Usually, when a request reaches you, it's expected that the following is true:

  • Its parameters have already been validated.
  • The user has already been authenticated, if possible.
  • User roles and permissions are known and the user is authorized to perform an action.

So, the code I initially wrote looked something like this:

data class Request(val email: String, val question: String)
fun handleRequest(r: Request) {
    // Validate...
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