I have a problem with JPA I will explain in detail:
I created a project in NetBeans “Java Application”, then right click on the package “Entity Classes From Data Base” I chose the DB, it’s good the entity is created with getters, setters and attributes of DB.
finally: right click on the same package “JPA Controller Classes From Entity Classes ” and I chose the entity created earlier, the file is generated with the methods of interaction with DB…
All is going well so far,
But when I run the project and after each operation (create, find, ..) the database is dumped and the program continues the execution without errors, for example if I chose to insert a new record in the DB , the other records are deleted and the record is inserted into the DB correctly! , I do not understand why, if one of you can explain this error it will be too cool…
here is my source code:
+Here I have a database its called "personne" containing only a one table also called "personne"(id=int,nom=varchar(30)).
+Testt.java (the main program) :
package testt;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import testt.exceptions.PreexistingEntityException;
public class Testt {
public static void main(String[] args) throws PreexistingEntityException, Exception {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("testtPU");
Personne p=new Personne(2);
p.setNom("ME ME");
PersonneJpaController tjc=new PersonneJpaController(emf);
tjc.create(p);
System.out.println("succeed! ");
}
}
Personne.java (the entity “personne” its created(generated) from the database):
package testt;
import java.io.Serializable;
import javax.persistence.*;
import javax.xml.bind.annotation.XmlRootElement;
@Entity
@Table(name = "PERSONNE", catalog = "", schema = "ROOT")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Personne.findAll", query = "SELECT p FROM Personne p"),
@NamedQuery(name = "Personne.findById", query = "SELECT p FROM Personne p WHERE p.id = :id"),
@NamedQuery(name = "Personne.findByNom", query = "SELECT p FROM Personne p WHERE p.nom = :nom")})
public class Personne implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@Column(name = "ID", nullable = false)
private Integer id;
@Column(name = "NOM", length = 30)
private String nom;
public Personne() {
}
public Personne(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getNom() {
return nom;
}
public void setNom(String nom) {
this.nom = nom;
}
@Override
public int hashCode() {
int hash = 0;
hash += (id != null ? id.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof Personne)) {
return false;
}
Personne other = (Personne) object;
if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
return false;
}
return true;
}
@Override
public String toString() {
return "testt.Personne[ id=" + id + " ]";
}
}
PersonneJpaController.java(generated from the “personne” entity)
package testt;
import java.io.Serializable;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Query;
import javax.persistence.EntityNotFoundException;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import testt.exceptions.NonexistentEntityException;
import testt.exceptions.PreexistingEntityException;
public class PersonneJpaController implements Serializable {
public PersonneJpaController(EntityManagerFactory emf) {
this.emf = emf;
}
private EntityManagerFactory emf = null;
public EntityManager getEntityManager() {
return emf.createEntityManager();
}
public void create(Personne personne) throws PreexistingEntityException, Exception {
EntityManager em = null;
try {
em = getEntityManager();
em.getTransaction().begin();
em.persist(personne);
em.getTransaction().commit();
} catch (Exception ex) {
if (findPersonne(personne.getId()) != null) {
throw new PreexistingEntityException("Personne " + personne + " already exists.", ex);
}
throw ex;
} finally {
if (em != null) {
em.close();
}
}
}
public void edit(Personne personne) throws NonexistentEntityException, Exception {
EntityManager em = null;
try {
em = getEntityManager();
em.getTransaction().begin();
personne = em.merge(personne);
em.getTransaction().commit();
} catch (Exception ex) {
String msg = ex.getLocalizedMessage();
if (msg == null || msg.length() == 0) {
Integer id = personne.getId();
if (findPersonne(id) == null) {
throw new NonexistentEntityException("The personne with id " + id + " no longer exists.");
}
}
throw ex;
} finally {
if (em != null) {
em.close();
}
}
}
public void destroy(Integer id) throws NonexistentEntityException {
EntityManager em = null;
try {
em = getEntityManager();
em.getTransaction().begin();
Personne personne;
try {
personne = em.getReference(Personne.class, id);
personne.getId();
} catch (EntityNotFoundException enfe) {
throw new NonexistentEntityException("The personne with id " + id + " no longer exists.", enfe);
}
em.remove(personne);
em.getTransaction().commit();
} finally {
if (em != null) {
em.close();
}
}
}
public List<Personne> findPersonneEntities() {
return findPersonneEntities(true, -1, -1);
}
public List<Personne> findPersonneEntities(int maxResults, int firstResult) {
return findPersonneEntities(false, maxResults, firstResult);
}
private List<Personne> findPersonneEntities(boolean all, int maxResults, int firstResult) {
EntityManager em = getEntityManager();
try {
CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
cq.select(cq.from(Personne.class));
Query q = em.createQuery(cq);
if (!all) {
q.setMaxResults(maxResults);
q.setFirstResult(firstResult);
}
return q.getResultList();
} finally {
em.close();
}
}
public Personne findPersonne(Integer id) {
EntityManager em = getEntityManager();
try {
return em.find(Personne.class, id);
} finally {
em.close();
}
}
public int getPersonneCount() {
EntityManager em = getEntityManager();
try {
CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
Root<Personne> rt = cq.from(Personne.class);
cq.select(em.getCriteriaBuilder().count(rt));
Query q = em.createQuery(cq);
return ((Long) q.getSingleResult()).intValue();
} finally {
em.close();
}
}
}
finally persistance.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="testtPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>testt.Personne</class>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/personne"/>
<property name="javax.persistence.jdbc.password" value="1234"/>
<property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
</properties>
</persistence-unit>
</persistence>
thank you in advance ^^
After the first run, you need to remove the line
from the persistance.xml file, otherwise EclipseLink will re-create the table each time. That’s why you find it empty. Check it out in the wiki.