Book Image

JBoss Weld CDI for Java Platform

By : Kenneth Finnigan
Book Image

JBoss Weld CDI for Java Platform

By: Kenneth Finnigan

Overview of this book

CDI simplifies dependency injection for modern application developers by taking advantage of Java annotations and moving away from complex XML, while at the same time providing an extensible and powerful programming model. "JBoss Weld CDI for Java Platform" is a practical guide to CDI's dependency injection concepts using clear and easy-to-follow examples. This will help you take advantage of the power behind CDI, as well as providing a firm understanding of how to use it within your applications. "JBoss Weld CDI for Java Platform" covers all the major aspects of CDI, breaking it down into understandable pieces. This book will take you through many examples of how these concepts can be utilized, helping you get up and running quickly and painlessly. "JBoss Weld CDI for Java Platform" gives you an insight into the different scopes provided by CDI and the use cases for which each has been designed. You will learn everything about dependency injection, scopes, events, producers, and more from JBoss Weld CDI, as well as how producers can create new beans for consumption within your application. You will also learn how to build a real world application with CDI using JSF and AngularJS for different web interfaces.
Table of Contents (17 chapters)
JBoss Weld CDI for Java Platform
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

The scope of a producer


Beans created by a producer defaults to be @Dependent scoped. A producer with no scope specified will be called each and every time Weld needs to inject a bean that is matched by the producer's bean types and qualifiers. It also means there will be a separate instance of the bean for each call made to the producer, which is not always what we want or intend.

CDI makes it easy for us to modify this behavior by adding any of @RequestScoped, @ConversationScoped, @SessionScoped, or @ApplicationScoped onto the producer, depending on which lifecycle we want for the produced bean. If we were to annotate a producer with @ApplicationScoped, the producer would only be called once for the life of the application, and the created bean is stored in the application context to be shared by all clients.

Note

A producer does not derive its scope from the bean in which it is declared.

An important point to remember when thinking of producers is that they are themselves a bean in their...