Book Image

Java 9 Dependency Injection

By : Nilang Patel, Krunal Patel
Book Image

Java 9 Dependency Injection

By: Nilang Patel, Krunal Patel

Overview of this book

Dependency Injection (DI) is a design pattern that allows us to remove the hard-coded dependencies and make our application loosely coupled, extendable, and maintainable. We can implement DI to move the dependency resolution from compile-time to runtime. This book will be your one stop guide to write loosely coupled code using the latest features of Java 9 with frameworks such as Spring 5 and Google Guice. We begin by explaining what DI is and teaching you about IoC containers. Then you’ll learn about object compositions and their role in DI. You’ll find out how to build a modular application and learn how to use DI to focus your efforts on the business logic unique to your application and let the framework handle the infrastructure work to put it all together. Moving on, you’ll gain knowledge of Java 9’s new features and modular framework and how DI works in Java 9. Next, we’ll explore Spring and Guice, the popular frameworks for DI. You’ll see how to define injection keys and configure them at the framework-specific level. After that, you’ll find out about the different types of scopes available in both popular frameworks. You’ll see how to manage dependency of cross-cutting concerns while writing applications through aspect-oriented programming. Towards the end, you’ll learn to integrate any third-party library in your DI-enabled application and explore common pitfalls and recommendations to build a solid application with the help of best practices, patterns, and anti-patterns in DI.
Table of Contents (14 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Summary


We have learned a few important points about the best practices and patterns for managing dependencies in this chapter. Though it is proven that DI brings greater flexibility and modularity in the code by decoupling the client code from its dependencies, there are a few things that we should follow to get the best out of it. 

In the beginning, we learned about patterns other than DI that help us to implement IoC. You can definitely use them in your code to decouple modules where the use of IoC containers is not possible. For example, in a legacy code where managing dependencies is not possible through an IoC container, these patterns are useful to achieve IoC.

We became familiar with various configuration options and learned how to choose the right one. We also saw the injection styles used in wiring the dependencies. When working with dependency management, one very obvious problem that occurs is circular reference, which causes circular dependency. We have observed what problems...