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

Adding logging ability


Let's start with using the logging API in Java to log messages to the console. As an example, we want to be able to log some sample messages during the application start and completion.

What we'd typically do in Java 8 or earlier is just import the necessary logging classes and start using the logging APIs. That is, the Logger class from the java.util.logging package. However, as we've learned in the previous chapter, there's an additional step in Java 9. Using the logging APIs directly will result in a compilation error. That's because the logging APIs aren't available in the java.base module. We've seen that the best way to search for a module is using the --list-modules parameter to the java command. Let's run that and see if we find a module related to logging:

$ java --list-modules 
... 
java.jnlp@9 
java.logging@9
java.management@9
java.naming@9
java.prefs@9

As you can see, there's a module called java.logging. That looks promising! The next step is to see if that...