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

A brief introduction to the Google Guice framework


We learned the benefits of DI in software engineering, but choosing a framework wisely is also important when implementing DI because each framework has its own advantages and disadvantages. There are various Java-based dependency injection frameworks available in the open source community, such as Dagger, Google Guice, Spring DI, JAVA EE 8 DI, and PicoContainer.

Here, we will learn in detail about Google Guice (pronounced juice), a lightweight DI framework that helps developers to modularize applications. Guice encapsulates annotation and generics features introduced by Java 5 to make code type-safe. It enables objects to wire together and tests with fewer efforts. Annotations help you to write error-prone and reusable code.

In Guice, the new keyword is replaced with @inject for injecting dependency. It allows constructors, fields, and methods(any method with multiple numbers of arguments) level injections. Using Guice, we can define custom...