Creating an Entity Class

As explained in Accessing Databases from Web Applications, an entity class is a component that represents a table in the database. In the case of the Duke’s Bookstore application, there is only one database table and therefore only one entity class: the Book class.

The Book class contains properties for accessing each piece of data for a particular book, such as the book’s title and author. To make it an entity class that is accessible to an entity manager, you need to do the following:

• Add the @Entity annotation to the class.

• Add the @Id annotation to the property that represents the primary key of the table.

• Add the @Table annotation to the class to identify the name of the database table if it is different from the name of the entity class.

• Optionally make the class Serializable.

The following code shows part of the Book class:

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="WEB_BOOKSTORE_BOOKS")

public class Book implements Serializable {

    private String bookId;
    private String title;

    public Book() { }

    public Book(String bookId, String title, ...) {
        this.bookId = bookId;
        this.title = title;
        ...
    }

    @Id
    public String getBookId() {
        return this.bookId;
    }

    public String getTitle() {
        return this.title;
    }
    ...

    public void setBookId(String id) {
        this.bookId=id;
    }

    public void setTitle(String title) {
        this.title=title;
    }
    ...
}