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

Pseudo scopes


Pseudo scopes result in beans that do not have a client proxy created by Weld, but instead a new instance is created each time and the client holds a direct reference to it. @Dependent is a scope annotation that is a pseudo scope type, and @Dependent is also the default scope for any beans that do not explicitly declare a scope.

Beans with a scope of @Dependent are never shared; it is a dependent object of whichever object it was injected into. This means that the @Dependent bean is created at the point when the object it belongs to is created, and is destroyed when the object it belongs to is destroyed.

Tip

Accessing a @Dependent bean by its EL name will cause a new instance of that bean to be created every time the expression is evaluated, which can be several times when using JSF. For this reason, it is not recommended to use @Dependent beans in EL expressions as it is likely that the desired behavior will not be achieved; instead, add the @Dependent bean to a normal scope...