OneToMany: list childs is null in prepersist method

pmercier · **Joined:** Thu Apr 24, 2008 9:33 am **Posts:** 3

Hibernate version: 3.2.6.ga
Hibernate entitymanager version: 3.3.1.ga
Hibernate annotations version: 3.3.0.ga
Mapping documents:

Hello everybody,

Here is my problem :
I have 2 entities : Parent and Child with a OneToMany (bi-directional)
In the parent class i declare a @PrePersist callback method that throw an RunTimeException when the number of childs is little than 2 or if the reference of the list is null.

In a testng class, I create a new object Parent and add it 2 childs[/b].
When I execute em.merge on the parent, the runtime exception is throwed by the PrePersist callback method.
=> the reference of the childs' list is null !!.

My question : "Is It normal ?"

Here is the Parent class :

Code:

package be.philou.test;

import java.io.Serializable;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.PrePersist;
import javax.persistence.PreUpdate;

@Entity
public class Parent implements Serializable {
   
   private static final long serialVersionUID = 4076893988337190107L;
   
   private int id;
   private String name;
   private String firstName;

   private List<Child> childs; 
   
   // -------------------------------------------------------------------------
   // getters & setters
   // -------------------------------------------------------------------------
   
   @Id 
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }

   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }

   public String getFirstName() {
      return firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }

   @OneToMany(mappedBy="parent", cascade=CascadeType.ALL)
   public List<Child> getChilds() {
      return childs;
   }
   public void setChilds(List<Child> childs) {
      this.childs = childs;
   }

   // -------------------------------------------------------------------------
   // callbacks
   // -------------------------------------------------------------------------

   @PrePersist
   @PreUpdate
   public void beforeCreate() {
      // Parent must have minimum 2 childs
      if (getChilds() == null || getChilds().size() < 2) {
         throw new RuntimeException("Parent must have minimum 2 childs");
      }
   }
   
}

Here is the Child class :

Code:

package be.philou.test;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
public class Child implements Serializable {
   private static final long serialVersionUID = 5120375761727811864L;
   
   private int id;
   private String info;
   
   private Parent parent;

   // -------------------------------------------------------------------------
   // getters & setters
   // -------------------------------------------------------------------------
   
   @Id 
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }

   public String getInfo() {
      return info;
   }
   public void setInfo(String info) {
      this.info = info;
   }

   @ManyToOne
   @JoinColumn(name="FK_PARENT")
   public Parent getParent() {
      return parent;
   }
   public void setParent(Parent parent) {
      this.parent = parent;
   }
   
   
}

hardy.ferentschik · **Posted:** Mon Apr 28, 2008 3:49 pm

Hi,

I am not quite sure where the problem is, but maybe it would help if you would post your test code?

--Hardy

pmercier · **Joined:** Thu Apr 24, 2008 9:33 am **Posts:** 3

Hi Hardy and thanks for your reply,

here is the test code
Note: the parentmanager.merge() simply call the em.merge() method

Code:

package be.philou.test;

import java.util.ArrayList;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.testng.AbstractTestNGSpringContextTests;
import org.testng.annotations.Test;

@ContextConfiguration(locations={"/spring-config.xml"})
@Test
public class ParentTest extends AbstractTestNGSpringContextTests {
   
   @Autowired private ParentManager parentManager;
   
   public void parentCreate() {
      Parent parent = new Parent();
      parent.setFirstName("firstName");
      parent.setName("name");
      parent.setChilds(new ArrayList<Child>());
      
      Child child;
      child = new Child();
      child.setInfo("child1");
      parent.getChilds().add(child);
      child.setParent(parent);
      
      child = new Child();
      child.setInfo("child2");
      parent.getChilds().add(child);
      child.setParent(parent);
      
      System.out.println("Childs count = " + parent.getChilds().size());
      parent = parentManager.merge(parent);
   }
   
}

hardy.ferentschik · **Posted:** Wed Apr 30, 2008 9:40 am

Hmm, I am not sure what goes wrong here. I assume your are using EntityManager.merge()? Have you tried using persist instead? You could also enable sql output to see if and which statements get executed.

--Hardy

pmercier · **Joined:** Thu Apr 24, 2008 9:33 am **Posts:** 3

Hi Hardy,

With the entitymanager's persist method, it works perfectly. It's only when i use the merge method.
I would like to have the same controls during persist or merge.
I have a alternative => execute the controls BEFORE the persist and merge call. (so, @PrePersist and @PreUpdate are no longer needed ...).

I think it's an hibernate's bug but i am not sure ...
Could you tell me how I can ask my question to someone from hibernate ?

Philippe.

hardy.ferentschik · **Posted:** Thu May 08, 2008 5:21 am

Hi Philippe,

I asked Emmanuel from the Hibernate team to have a look at this. If you don't hear anything you could always create a Jira issue to get someone to look at it.

--Hardy

emmanuel · **Posted:** Thu May 08, 2008 10:45 am

It might be due to the way we order merges: ie pre-persist being called on the clone version before the children merge. It is worth opening a JIRA issue with a minimal test case.
My bet is that it's going to be a tough one to fix.

I am curious, if you use Hibernate Validator, does

@NotNull @Size(min=2) Collection children;

work or does it fail as well?