Private Constructor, no error?

[hamada yam]

It's mentioned in the JPA spec 2_0 that an entity must have a no-arg constructor and it should be public or protected. I changed the visibility to private and everything(persistence logic) works fine. I am able to save and retrieve object without any warning/error. Why so? I am using Mysql and hibernate 4.3-6.Final as JPA provider. The same goes for final class , i made my Entity final and it still works.

import javax.persistence.Entity;
import javax.persistence.Id;
import java.math.BigDecimal;
@Entity
public final class Employee {
@Id
private int id;
private String name;
private BigDecimal salary;
private Employee() {}
public Employee(int id, String name) {this.id = id;this.name = name;}
public BigDecimal getSalary() {return salary;}
public void setSalary (BigDecimal salary) {this.salary = salary;}
public String toString() {return id + ":" + name+":"+ salary;}
}

But if i call clear() method on em , and perform some action on entity then i get Runtime exception related with private constructor
e.g.

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.EntityManager;
import java.math.BigDecimal;
import javax.persistence.TypedQuery;
import java.util.List;
public class Test {
public static void main (String... args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("empPU");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Employee e = new Employee(1, "john");
em.persist(new Employee(2, "paul"));
em.persist(e);
em.getTransaction().commit();
System.out.println("-----Created Employee-------");
Employee f = em.find(Employee.class, 1);
//if i uncomment the em.clear() , then i get RuntimeException regarding private constructor on q.getResultList(), see below where the method is used
//em.clear();
em.getTransaction().begin();
f.setSalary(new BigDecimal("100.20"));
em.getTransaction().commit();
System.out.println("------Updated Employee---------");
System.out.println("Found " + f);
System.out.println("-----Find all employess--------");
TypedQuery<Employee> q = em.createQuery("Select e from Employee e", Employee.class);
List<Employee> emps = q.getResultList();
}
}

Can someone please explain why the code above behaves like this?
Thanks

[Frits Walraven]

 

I changed the visibility to private and everything(persistence logic) works fine. I am able to save and retrieve object without any warning/error. Why so?

That means that your JPA implementation is not obeing the JPA specifications (by the way: hibernate 4.3-x is JPA 2.1)

I created a small example and tested it with the openjpa implementation and I got the expected error:

Exception in thread "main" <openjpa-2.3.0-r422266:1540826 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: [Error while processing persistent type nl.notes.jpa.Person, declared in \nl\notes\jpa\Person.java. Error details: Unenhanced classes must have a public or protected no-args constructor. Type nl.notes.jpa.Person's no-args constructor is private or package-visible.

[hamada yam]

Thanks, for exam purpose should i use openJPA 2.0 as an implementation in order to get the same behavior as mentioned in JPA specification?

[Frits Walraven]

Yes, I haven't found any problem (yet) with the OpenJPA implementation.