A round trip working with objects

Hibernate may be regarded as a persistence provider to JPA:

Figure 937. JPA persistence provider

Todo: Ref/Jdbc/persistProvider.fig


The following class hibintro.v1.model.User will be used as a starting example to be mapped to a database. Notice the javax.persistence.Entity annotation ❶:

Figure 938. Mapping hibintro.v1.model.User instances to a database. 
package hibintro.v1;

import javax.persistence.Entity;
import javax.persistence.Id;

/**
 * A simple class intended to be mapped to a database server
 *
 */
@Entity ❶
public class User {

  String uid;
  /**
   * @return  The user's unique login name e.g. "goik"
   */
  @Id
  public String getUid() {
    return uid;
  }
  /**
   * @param uid See {@link #getUid()}.
   */
  public void setUid(String uid) {
    this.uid = uid;
  }
  String cname;
  /**
   * @return The user's common name e.g. "Martin Goik"
   */
  public String getCname() {
    return cname;
  }
  /**
   * @param cname See {@link #getCname()}.
   */
  public void setCname(String cname) {
    this.cname = cname;
  }

  /**
   * Hibernate/JPA require a default constructor. It has has to be
   * implemented if any non-default constructor has been defined
   */
  public User() {}

  /**
   * @param uid See {@link #getUid()}.
   * @param cname See {@link #getCname()}.
   */
  public User(String uid, String cname) {
    this.uid = uid;
    this.cname = cname;
  }
}

With respect to Figure 936, “A basic persistence.xml JPA configuration file. ” we notice our class hibintro.v1.model.User being referenced: 

<persistence ... >

    <persistence-unit name="hibintroV1PU">
        <class>hibintro.v1.User</class>
        ...
    </persistence-unit>
     ...

This line tells Hibernate to actually map hibintro.v1.model.User to the database.

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