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

Defining a custom constraint


With the bean validation API, you can also introduce custom constraints, rather than the built-in ones, in order to reuse more complex validation logic in different contexts within your application. This is one of the best features and introduces a great flexibility and reusability in real-world validation scenarios.

Let's introduce a custom constraint, called CheckCase, which is used to check whether a string is uppercase or lowercase, according to the developer's preference. The constraint will include a type attribute, which will be given either the value of UPPER or LOWER. If the type attribute was given the UPPER value, then it will check the given string to see if it's in uppercase or not. Otherwise, if it was given the LOWER value, then it will check if the given string is in lowercase or not.

To define this custom constraint, we will perform two key steps:

  1. Creating a constraint annotation.
  2. Creating a validator class associated with this annotation.

Let's perform...