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Step 2: Define a JPA Entity Class

To store objects in an ObjectDB database using JPA we need to define an entity class:

  • Open the [New Java Class] dialog box, e.g. by right clicking the project node
    (in the [Package Explorer] window) and selecting New > Class.
  • Enter guest as the package name - use exactly that case sensitive package name.
  • Enter Guest as the class name - use exactly that case sensitive class name.
  • Click Finish to create the new class.

The new class should represent Guest objects in the database.

Use copy and paste to replace the new source file content with the following code:

package guest;
 
import java.io.Serializable;
import java.sql.Date;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
 
@Entity
public class Guest implements Serializable {
    private static final long serialVersionUID = 1L;
 
    // Persistent Fields:
    @Id @GeneratedValue
    Long id;
    private String name;
    private Date signingDate;
 
    // Constructors:
    public Guest() {
    }
 
    public Guest(String name) {
        this.name = name;
        this.signingDate = new Date(System.currentTimeMillis());
    }
 
    // String Representation:
    @Override
    public String toString() {
        return name + " (signed on " + signingDate + ")";
    }
} 

The new class should represent Guest objects in the database. Besides the @Entityjavax.persistence.EntityJPA annotationSpecifies that the class is an entity.
See JavaDoc Reference Page...
annotation and the id field (and its annotations) - the Guest class is an ordinary Java class.

The next step is adding a context listener class that will manage a JPA's EntityManagerFactory representing the ObjectDB database.