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

How does WebSockets work?


Let's see how the WebSockets protocol works over HTTP. For a client to establish a connection to a web server using WebSockets, it first performs a WebSocket handshake request, which is very similar to a normal HTTP request, but with the Upgrade header, as follows:

GET /path/to/endpoint HTTP/1.1 
Host: localhost 
Upgrade: websocket 
Connection: Upgrade 
Sec-WebSocket-Key: xqBt3ImNzJbYqRINxEFlkg== 
Origin: http://localhost 
Sec-WebSocket-Version: 13 

As you can see, the upgrade header, with some other WebSockets-related headers, is used to perform what's called a WebSockets handshake. The handshake request asks the server to use the WebSockets protocol.

If the web server supports the WebSockets protocol on this path, it should respond with the following handshake response:

HTTP/1.1 101 Switching Protocols 
Upgrade: websocket 
Connection: Upgrade 
Sec-WebSocket-Accept: K7DJLdLooIwIG/MOpvWFB3y3FE8= 

The connection switches to a bi-directional type, and the connection lasts...