Book Image

Java 9 Programming By Example

By : Peter Verhas
Book Image

Java 9 Programming By Example

By: Peter Verhas

Overview of this book

This book gets you started with essential software development easily and quickly, guiding you through Java’s different facets. By adopting this approach, you can bridge the gap between learning and doing immediately. You will learn the new features of Java 9 quickly and experience a simple and powerful approach to software development. You will be able to use the Java runtime tools, understand the Java environment, and create Java programs. We then cover more simple examples to build your foundation before diving to some complex data structure problems that will solidify your Java 9 skills. With a special focus on modularity and HTTP 2.0, this book will guide you to get employed as a top notch Java developer. By the end of the book, you will have a firm foundation to continue your journey towards becoming a professional Java developer.
Table of Contents (17 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Service classes

We have two service classes. These classes serve the controllers with data and implement the business logic, no matter how simple they are. One of the service class implementations calls REST-based services, while the other one reads data from properties files. The latter can be used to test the application offline. The one that calls REST services is used in the production environment. Both of them implement the ProductLookup interface:

import java.util.List; 
public interface ProductLookup { 
    ProductInformation byId(String id); 
    List<String> byQuery(String query); 

ResourceBasedProductLookup stores the whole database in a map called products. It is filled from the properties files when one of the service methods is invoked. The private method loadProducts is invoked from each of the service methods when they start, but it loads the data only if it is not loaded yet: