Whats wrong with the code ?

[Nikhil Jain]

    
package src.db;
 
import java.io.Serializable;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
 
@Entity
@Table(name = "creditcard")
public class CreditCard implements Serializable {
 
private static final long serialVersionUID = 1L;

private int id;
 
private int number;

//private int empId;

 
@Column(name = "NO")
public int getNumber() {
return number;
}
 
public void setNumber(int number) {
this.number = number;
}
 
@Id
@Column(name = "ID") @GeneratedValue
public int getId() {
return id;
}
 
public void setId(int id) {
this.id = id;
}
 
//Foregin Key
/*@Column(name = "EMPID")
public int getEmpId() {
return empId;
}
 
public void setEmpId(int empId) {
this.empId = empId;
}*/
 
}
 

package src.db;
 
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
 
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
 
@Entity
@Table(name = "employee")
public class Employee implements Serializable {
 
/**
 * 
 */
private static final long serialVersionUID = 1L;
 
private int id;
 
private String name;
 
private int age;
 
private Collection<CreditCard> creditCards = new ArrayList<CreditCard>();
 
@Id
@Column(name = "ID") @GeneratedValue
public int getId() {
return id;
}
 
public void setId(int id) {
this.id = id;
}
 
@Column(name = "AGE")
public int getAge() {
return age;
}
 
public void setAge(int age) {
this.age = age;
}
 
@Column(name = "NAME")
public String getName() {
return name;
}
 
public void setName(String name) {
this.name = name;
}

@OneToMany(cascade={CascadeType.PERSIST, CascadeType.REMOVE})
@JoinColumn(name="empid")
public Collection<CreditCard> getCreditCards() {
return creditCards;
}
 
public void setCreditCards(Collection<CreditCard> creditCards) {
this.creditCards = creditCards;
}
 
}
 

public void testOneToMany() {
Employee emp = new Employee();
emp.setAge(29);
emp.setName("Raj");

CreditCard cc1 = new CreditCard();
cc1.setNumber(2);
emp.getCreditCards().add(cc1);

CreditCard cc2 = new CreditCard();
cc2.setNumber(22);
emp.getCreditCards().add(cc2);

CreditCard cc3 = new CreditCard();
cc3.setNumber(1);
emp.getCreditCards().add(cc3);

this.persistObject(emp);

/*  EntityManagerFactory factory = Persistence.createEntityManagerFactory("employee");
EntityManager em = factory.createEntityManager();
EntityTransaction et = em.getTransaction();
Employee emp = em.find(Employee.class, 99165);

if (emp != null)
{
System.out.println(emp.getName());
et.begin();
em.remove(emp);
et.commit();
}*/

}
 
public void persistObject(Object object) {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("employee");
EntityManager em = factory.createEntityManager();
EntityTransaction et = em.getTransaction();
et.begin();
em.persist(object);
et.commit();
factory.close();
}

What is the problem with the above code? The enties works well when I try to persist them in isolation. I am trying to persister these objects in a single trasaction.

There is no problem with the database, as it works well when executed by persisting the objects one by one ...

[Mike Keith]

1) Bad karma to access the EM from within the entity class.

2) Your relationship is not properly mapped. Try this:

@Entity
public class CreditCard implements Serializable {
    ...
    Employee emp;
    ...
    @ManyToOne
    public Employee getEmp() { return emp; }
    public void setEmp(Employee emp) { this.emp = emp; }
}
 
@Entity
public class Employee implements Serializable {
    ...
    Collection<CreditCard> creditCards = new ArrayList<CreditCard>();
    ... 
    @OneToMany(mappedBy="emp", cascade={CascadeType.PERSIST})
    public Collection<CreditCard> getCreditCards() { return creditCards; }
    public void setCreditCards(Collection<CreditCard> creditCards) {
        this.creditCards = creditCards;
    }
}

3. You should probably set the id in employee to not be generated so you can assign it when you create one and then use the assigned id value to find it later on. Otherwise you won't know what id value got assigned to the employee unless you hold on to it, etc.