import org.codehaus.groovy.grails.orm.hibernate.cfg.GrailsAnnotationConfiguration
class DevelopmentDataSource {
   def configClass = GrailsAnnotationConfiguration.class
   … // remaining properties
}

package com.books;
@Entity
public class Book {
    private Long id;
    private String title;
    private String description;
    private Date date;
    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
}

<hibernate-configuration>
    <session-factory>
        <mapping package="com.books" />
        <mapping class="com.books.Book" />
    </session-factory>
</hibernate-configuration>