Book Image

Spring Essentials

Book Image

Spring Essentials

Overview of this book

Spring is an open source Java application development framework to build and deploy systems and applications that run on the JVM. It is the industry standard and the most popular framework among Java developers with over two-thirds of developers using it. Spring Essentials makes learning Spring so much quicker and easier with the help of illustrations and practical examples. Starting from the core concepts of features such as inversion of Control Container and BeanFactory, we move on to a detailed look at aspect-oriented programming. We cover the breadth and depth of Spring MVC, the WebSocket technology, Spring Data, and Spring Security with various authentication and authorization mechanisms. Packed with real-world examples, you’ll get an insight into utilizing the power of Spring Expression Language in your applications for higher maintainability. You’ll also develop full-duplex real-time communication channels using WebSocket and integrate Spring with web technologies such as JSF, Struts 2, and Tapestry. At the tail end, you will build a modern SPA using EmberJS at the front end and a Spring MVC-based API at the back end.By the end of the book, you will be able to develop your own dull-fledged applications with Spring.
Table of Contents (14 chapters)
Spring Essentials
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Broadcasting a message to a single user in a WebSocket application


In the previous section, we saw a WebSocket application of the multiple subscriber model, in which a broker sent messages to a topic. Since all clients had subscribed to the same topic, all of them received messages. Now, you are asked to develop an application that targets a specific user in a WebSocket chat application.

Suppose you want to develop an automated answering application in which a user sends a question to the system and gets an answer automatically. The application is almost the same as the previous one (STOMP over WebSocket and the fallback option in Spring 4), except that we should change the WebSocket configurer and endpoint on the server side and subscription on the client side. The code for the AutoAnsweringWebSocketMessageBrokerConfigurer class is:

@Configuration
@EnableWebSocketMessageBroker
public class AutoAnsweringWebSocketMessageBrokerConfigurer extends AbstractWebSocketMessageBrokerConfigurer {
  ...