Erro com JPA ! Column 'MESSAGE_ID' cannot be null [RESOLVIDO]

Assuntos Gerais
#1

Olá ! Estou estudando o livro Java Persistence with Hibernate e tentando fazer o primeiro exemplo funcionar usando JPA. Ele faz um projeto HelloWorld primeiramente com hibernate sem JPA, que no meu caso deu tudo certo, porém quando tento fazer o mesmo com a JPA tenho o seguinte erro:

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not insert: [hello.Message]
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1214)
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1147)
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1153)
	at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:678)
	at hello.HelloWorld.main(HelloWorld.java:27)
Caused by: org.hibernate.exception.ConstraintViolationException: could not insert: [hello.Message]
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
	at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
	at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2345)
	at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2852)
	at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
	at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
	at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
	at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
	at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
	at org.hibernate.ejb.event.EJB3PersistEventListener.saveWithGeneratedId(EJB3PersistEventListener.java:69)
	at org.hibernate.event.def.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:179)
	at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
	at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:61)
	at org.hibernate.impl.SessionImpl.firePersist(SessionImpl.java:808)
	at org.hibernate.impl.SessionImpl.persist(SessionImpl.java:782)
	at org.hibernate.impl.SessionImpl.persist(SessionImpl.java:786)
	at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:672)
	... 1 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'MESSAGE_ID' cannot be null
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
	at com.mysql.jdbc.Util.getInstance(Util.java:381)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3558)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3490)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648)
	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2362)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2280)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2265)
	at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)
	at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
	at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
	... 16 more

Classe Message

package hello;

import javax.persistence.*;

@Entity
@Table(name = "MESSAGES")
public class Message 
{
	@Id @GeneratedValue
	@Column(name = "MESSAGE_ID")
	private Long id;
	
	@Column(name = "MESSAGE_TEXT")
	private String text;
	
	@ManyToOne(cascade = CascadeType.ALL)
	@JoinColumn(name = "NEXT_MESSAGE_ID")
	private Message nextMessage;
	
	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;
	}
}

Classe HelloWorld

package hello;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

public class HelloWorld {
	public static void main(String[] args) 
	{
		
		// Start EntityManagerFactory
		EntityManagerFactory emf = Persistence.createEntityManagerFactory("helloworld");
		
		// First unit of work
		EntityManager em     = emf.createEntityManager();
		EntityTransaction tx = em.getTransaction();
		
		tx.begin();
		
		Message message = new Message("Hello World");
		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());
		}
		
		newTx.commit();
		newEm.close();
		
		// Shutting down the application
		emf.close();
	}
}

Eu criei as tabelas usando o codigo:

Configuration cfg = new Configuration().configure();
SchemaExport schemaExport = new SchemaExport(cfg);
schemaExport.create(false, true);

O SQL que é executado é esse:

insert 
    into
        MESSAGES
        (MESSAGE_ID, NEXT_MESSAGE_ID, MESSAGE_TEXT) 
    values
        (null, ?, ?)

Depois, dá o erro citado. Ele está tentando inserir no banco um record com chave primaria nula, alguem sabe porque ? Obrigado.

#2

Bom galera, resolvi. O problema era que eu ainda estava usando o arquivo hibernate.cfg.xml, foi só passar tudo para o persistence.xml que o problem sumiu. Abraços.

#3