The first thing you need to know about the JPA is that it is a specification, not an implementation. There are several implementations, Hibernate and EclipseLink arguably being the most popular ones. In this book, we'll use Hibernate. The other things you need to learn about JPA are better learned by coding! Let's see how to create a simple Vaadin application that shows a Grid with the messages in the database.
What do you think is the first thing you need to do to start using JPA, or more specifically, Hibernate? It's, of course, adding the dependencies. Create a Vaadin project and add the following dependencies to your pom.xml file:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.2.10.Final</version>
</dependency>
You can...