@Column(name = "MESSAGE_TEXT")
private String text;
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name =
"NEXT_MESSAGE_ID")
private Message nextMessage;
public Message() {
}
public Message(String text) {
this.text = text;
}
public Long getId() {
return id;
}
private void setId(Long id) {
this.id = id;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public Message getNextMessage() {
return nextMessage;
}
public void setNextMessage(Message
nextMessage) {
this.nextMessage = nextMessage;
}
}

Here "Message" class is mapped to "MESSAGES" table, "id", "text" and "nextMessage" properties - to "MESSAGE_ID", "MESSAGE_TEXT" and "NEXT_MESSAGE_ID" fields.

2. Now create a simple program ( HelloWorld.java ) that uses persistent "Message" object:

HelloWorld.java
package hello;
import java.util.*;
import javax.persistence.*;
public class HelloWorld {
public static void main
(String[] args) {
// Start EntityManagerFactory
EntityManagerFactory emf =
Persistence.createEntity
ManagerFactory("helloworld");
// First unit of work
EntityManager em =
emf.createEntityManager();
EntityTransaction tx =
em.getTransaction();
tx.begin();
Message message =
new Message("Hello
World with JPA");
em.persist(message);
message = new Message("This is message 2");
em.persist(message);
message = new Message("This is message 3");
em.persist(message);
tx.commit();
em.close();
// Second unit of work
EntityManager newEm =
emf.createEntityManager();
EntityTransaction newTx =
newEm.getTransaction();
newTx.begin();
List messages = newEm.createQuery
("select m from Message m order by m.text
asc").getResultList();
System.out.println
( messages.size() + " message(s) found:" );
for (Object m : messages) {
Message loadedMsg = (Message) m;
System.out.println
(loadedMsg.getText());
}

Download Maven2JPA Source Code