Book Image

Java 9 Dependency Injection

By : Nilang Patel, Krunal Patel
3 (1)
Book Image

Java 9 Dependency Injection

3 (1)
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

Binding in Guice


In the previous topic, we became acquainted with the binding process and its importance in Guice DI. Each binding call to the bind() method is type-checked, so the compiler can report mistakes in case you utilize off-base types.

Guice provides different types of binding techniques which can be used in modules. The types of binding available are: linked bindings, instance bindings; untargeted bindings. Constructor bindings, built-in bindings, Just-in-time bindings. and provider bindings.

Linked bindings

Linked binding helps to map a type to its implementation. Examples of linked bindings include an interface to its implementation class, and a superclass to a subclass.

Here, NotificationService is bound to the SMSService instance in the ApplicationModule class. This binding affirmation binds an interface to its implementation:

   bind(NotificationService.class).to(SMSService.class);

When we call injector.getInstance(ApplicationModule.class),it will utilize SMSService. If binding...