Book Image

Developing Middleware in Java EE 8

Book Image

Developing Middleware in Java EE 8

Overview of this book

Middleware is the infrastructure in software based applications that enables businesses to solve problems, operate more efficiently, and make money. As the use of middleware extends beyond a single application, the importance of having it written by experts increases substantially. This book will help you become an expert in developing middleware for a variety of applications. The book starts off by exploring the latest Java EE 8 APIs with newer features and managing dependencies with CDI 2.0. You will learn to implement object-to-relational mapping using JPA 2.1 and validate data using bean validation. You will also work with different types of EJB to develop business logic, and with design RESTful APIs by utilizing different HTTP methods and activating JAX-RS features in enterprise applications. You will learn to secure your middleware with Java Security 1.0 and implement various authentication techniques, such as OAuth authentication. In the concluding chapters, you will use various test technologies, such as JUnit and Mockito, to test applications, and Docker to deploy your enterprise applications. By the end of the book, you will be proficient in developing robust, effective, and distributed middleware for your business.
Table of Contents (18 chapters)
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Preface
Index

Using producers


As shown earlier, a bean can have different alternatives, by introducing one interface and providing different implementations, each with a different qualifier. When injecting a reference to this interface in another bean, you can annotate your injection point with the qualifier for the implementation you desire. One interesting question is, can we specify which implementation to inject according to some runtime parameters, such as a user-specified choice?

For example, suppose a user is engaged in a payment workflow process. The first step is that the user will choose which payment method they prefer and where the next step they will actually perform the payment transaction. Suppose you have a PaymentStrategy interface with different bean implementations for a credit card, PayPal, and check payment strategies. Can we specify which bean implementation to reference according to the user choice? The answer is yes! This is called runtime polymorphism, and it can be achieved using...