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 started the chapter with a Spring bean definition attribute, which is important to learn as the whole IoC container is a relay on bean initialization. After that we learned the classification of scope with syntax. 

On our journey, we learned how scope is configured using XML metadata and Java configuration in Spring. Without dependency injection, we cannot complete the chapter. That's why, by writing a Spring Boot application, we try to understand how the main scopes work in standalone as well as in web applications.

We intentionally skipped the scope topic in Chapter 4, Dependency Injection with Google Guice. So, we have covered the Google Guice scope in this chapter with basic scopes. Spring and Google Guice have almost the same scope, but the default behavior of object initialization is different. Spring creates instances with the singleton, whereas Guice creates with the prototype scope. 

In the next chapter, we will look at an important feature called aspect-oriented programming...