Book Image

Getting Started with Oracle WebLogic Server 12c: Developer's Guide

Book Image

Getting Started with Oracle WebLogic Server 12c: Developer's Guide

Overview of this book

Oracle WebLogic server has long been the most important, and most innovative, application server on the market. The updates in the 12c release have seen changes to the Java EE runtime and JDK version, providing developers and administrators more powerful and feature-packed functionalities. Getting Started with Oracle WebLogic Server 12c: Developer's Guide provides a practical, hands-on, introduction to the application server, helping beginners and intermediate users alike get up to speed with Java EE development, using the Oracle application server. Starting with an overview of the new features of JDK 7 and Java EE 6, Getting Started with Oracle WebLogic Server 12c quickly moves on to showing you how to set up a WebLogic development environment, by creating a domain and setting it up to deploy the application. Once set up, we then explain how to use the key components of WebLogic Server, showing you how to apply them using a sample application that is continually developed throughout the chapters. On the way, we'll also be exploring Java EE 6 features such as context injection, persistence layer and transactions. After the application has been built, you will then learn how to tune its performance with some expert WebLogic Server tips.
Table of Contents (18 chapters)
Getting Started with Oracle WebLogic Server 12c: Developer's Guide
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Using a singleton service


Java EE provides singletons through the use of the @Singleton annotation. In practice, this annotation will guarantee that your class will be loaded only once per JVM or per application server instance. Although this is a powerful feature, if your business scenario can't cope with this behavior (duplicate component instances, one per JVM), you need another approach; the singleton service offered by WebLogic can offer an elegant solution for such cases. This feature guarantees that a given singleton class will have only one instance across a cluster, automatically managing failover and migration to another server instance in case of failure.

In the singleton ReservationCodeBean class there is a functionality that generates control numbers used to identify the reservations. The actual implementation is perfectly fine for a single server application, but running this application on multiple servers will end up creating several instances of ReservationCodeBean, one per...