Common JPA annotations

In this chapter, we will create entities to represent a forum application. The main entities involved in a forum are the forum itself (which exposes the argument), the topic that exposes the questions of the argument, the posts (the responses), and the category of a forum.

So we can start with the upper level, the category:

@Entity
@Table(name = "JBP_FORUMS_CATEGORIES")
public class Category implements Serializable {
       @Id
       @Column(name = "JBP_ID")
       @GeneratedValue
       private Integer id;
}

The @Entity annotation specifies that the bean we have written is an entity. An entity is an object representing a table in a relational database. The @Table annotation maps the entity to the relational table of a database. If the @Table is not specified, the entity will be mapped with a relational table represented by the simple name of the class, in the case of the example it will be Category.

In this sample we have specified the primary key of the table thanks...