Clean Code Principles and Patterns is one of the most comprehensive no-fluff guides for software developers to help them write clean code every day. The author Petri Silen has almost 30 years of industry experience in designing and implementing software, and now he puts all his knowledge gained during the years into this book. The book is packed with principles and patterns that help developers, from novices and juniors to seniors and experts, to write cleaner code. The principles and patterns presented in the book are accompanied by realistic yet straightforward examples to help the reader to understand them better. Examples are written in Java, JavaScript/TypeScript, and C++. Most of the examples are directly applicable to other programming languages, too. The reader should have basic knowledge of one object-oriented programming language to get the full benefit from this book. The source code for all major examples presented in the book is available in a public GitHub repository.

After reading this book, you will know the following and much more:

• How to design modern cloud-native microservices
• What are autopilot microservices
• What are event sourcing, CQRS, distributed transactions, saga orchestration pattern, and saga choreography pattern
• What are the five SOLID principles, and how to put them into use in real-life code
• What are the 25 design patterns, and how to use them
• What is the MVC pattern, and how MVP and MVVM differ from each other
• How to achieve a clean design for a microservice
• Why and how to use dependency injection
• Detailed instructions with concrete examples on how to uniformly name various software entities like classes, functions, and variables
• Why you should prefer composition over inheritance
• How to split a software system into domains using domain-driven design
• How to organize a source code repository
• How to organize code into directories
• Concrete ways how to avoid writing comments and refactor comments away
• What are the most common issues that static code analyzers find, and how to correct them
• Most important refactoring techniques for everyday use
• Why you should use a statically typed language
• How to correctly handle errors and exceptions
• How to not forget handle errors and exceptions
• Why you should never pass or return a null value
• How to avoid off-by-one errors effectively
• What you should remember when using a Google search to get answers
• When and how to optimize code
• TDD, Unit testing, mocking, integration testing, E2E testing, and non-functional testing
• What is threat modeling and how to conduct it
• Authentication and authorization using OpenID Connect and OAuth2
• What are the essential security features to implement in an application
• How to design APIs using technologies like JSON-RPC, REST, GraphQL, SSE, WebSocket, gRPC, and event-driven services
• When and how to use a relational database, document database, key-value store, or wide-column database
• How to avoid SQL injection attacks using ORM or parameterized SQL queries
• When to use threading or parallel algorithms and how to ensure thread safety
• What principles to follow when working in a software development team
• What are DevOps, SecOps, and continuous integration (CI), and what is the difference between continuous delivery (CD) and continuous deployment (CD)

Table of Contents

1: About the Author

2: Introduction

3: Architectural Principles and Patterns

4: Object-Oriented Design Principles

5: Coding Principles

6: Testing Principles

7: Security Principles

8: API Design Principles

9: Databases And Database Principles

10: Concurrent Programming Principles

11: Agile and Teamwork Principles

12: DevSecOps

13: Conclusion

14: Appendix A

About the Author

Petri Silen is a seasoned software developer working at Nokia Networks in Finland with industry experience of almost 30 years. He has done both frontend and backend development with a solid competence in multiple programming languages, including C++, Java, and JavaScript/TypeScript. He started his career at Nokia Telecommunications in 1995. During his first years, he developed a real-time mobile networks analytics product called "Traffica" in C++ for major telecom customers worldwide, including companies like T-Mobile, Orange, Vodafone, and Claro. The initial product was for monitoring a 2G circuit-switched core network and GPRS packet-switched core network. Later, functionality to Traffica was added to cover new network technologies, like 3G circuit-switched and packet core networks, 3G radio networks, and 4G/LTE. He later developed new functionality for Traffica using Java and web technologies, including jQuery and React. During the last few years, he has developed cloud-native containerized microservices with Java and C++ for the next-generation Customer and Networks Insights (CNI) product used by major communications service providers like Verizon, AT&T, USCC, and KDDI. The main application areas he has contributed during the last years include KPI-based real-time alerting, anomaly detection for KPIs, and configurable real-time data exporting.

During his free time, he has developed a data visualization application using React, Redux, TypeScript, and Jakarta EE. He has also developed a security-first cloud-native microservice framework for Node.js in TypeScript. He likes to take care of his Kaapo cat, take walks, play tennis and badminton, ski in the winter, and watch soccer and ice hockey on TV.