Book Image

Modular Programming in Java 9

By : Koushik Srinivas Kothagal
Book Image

Modular Programming in Java 9

By: Koushik Srinivas Kothagal

Overview of this book

The Java 9 module system is an important addition to the language that affects the way we design, write, and organize code and libraries in Java. It provides a new way to achieve maintainable code by the encapsulation of Java types, as well as a way to write better libraries that have clear interfaces. Effectively using the module system requires an understanding of how modules work and what the best practices of creating modules are. This book will give you step-by-step instructions to create new modules as well as migrate code from earlier versions of Java to the Java 9 module system. You'll be working on a fully modular sample application and add features to it as you learn about Java modules. You'll learn how to create module definitions, setup inter-module dependencies, and use the built-in modules from the modular JDK. You will also learn about module resolution and how to use jlink to generate custom runtime images. We will end our journey by taking a look at the road ahead. You will learn some powerful best practices that will help you as you start building modular applications. You will also learn how to upgrade an existing Java 8 codebase to Java 9, handle issues with libraries, and how to test Java 9 applications.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Summary


In this chapter, we've taken a detailed look at the services feature in the Java module system. We've learned the disadvantages of tight coupling of modules, and how loose coupling provides more flexibility. We then dove right into the syntax of creating and using services and then implemented a sorting service with two provider implementations. We then looked at some advanced concepts related to services, such as mechanisms for prioritizing service instances, using the service interface itself to handle service lookup, and deferring service instance creation using the Provider type in the case of heavy-weight services.

We then revisited the two goals of modularity--strong encapsulation and dependency injection--and evaluated how the services feature impacts those goals.

In the next chapter, we'll learn about the new linking phase that now applies to Java development thanks to modularity features. We'll also revisit the problem of the monolithic JDK that we discussed in Chapter 1,...