EJB3 and composite primary key:ids for this class must be ma

khalidhajsaleh · **Joined:** Tue Aug 09, 2005 3:03 pm **Posts:** 14

Hi,

I am not sure if this is the correct forum to ask the question. I am trying to run an example with EJB3 on jboss with HSQL database.

I am getting the error: "ids for this class must be manually assigned before calling save" when i try to save a class with a composite pk.

It is obvious that the container is expecting to set the my pk before saving. Here is the problem: The composite key contains two fields. I wanted to generate one of the fields myself but let the system generate the other field in the key. Here is my code

my pk:

Code:

@Embeddable(access = AccessType.FIELD)
public class CategoryPK implements Serializable {

private int id;
private String type;

  //this is the key I wanted auto generate
  public int getId() {
return id;
}

  //this is the key I wanted the user to input
public String getType() {
return type;

public boolean equals(Object obj){\\some code}
  public int hashCode() {\\some code}

}
}

My class

Code:

@Entity 
@Table(name = "Catgory") 
public class Category implements Serializable { 

private CategoryPK categoryPK; 
private String description; 

// my pk 
@Id(generate = GeneratorType.NONE) 
public CategoryPK getCategoryPK() { 
return categoryPK; 
} 
} 

Any suggestions?

scesbron · **Joined:** Thu Sep 04, 2003 8:23 am **Posts:** 368

Default generators in Hibernate are for simple id fields. If you want hibernate to generate half of your composite id, you may try to create your own custom generator based on hibernate ones. Take a look at the classes in the org.hibernate.id package to see how you can write a generator.

Be careful, in your case, you will create and assigned your id instance to your domain object. Your generator will have to get this object, check if the field it generates is null and then give it a value. I don't know what kind of unsaved-value you define in this case.

Seb

khalidhajsaleh · **Joined:** Tue Aug 09, 2005 3:03 pm **Posts:** 14

What if I want to auto generate both fields of my composite primary key. Is there a way to do that? it seems that when using composite keys, the standard set assumes that user will provice all of the key attributes.

Khalid

scesbron · **Joined:** Thu Sep 04, 2003 8:23 am **Posts:** 368

It is true that in the hbm grammar, the generator tag is only defined inside id tag.
So, if you want to generate both fields, you can define an id instead of a composite-id like that

Code:

        <id
            name="id"
            type="com.MyCategoryPkType"
            unsaved-value="none"
        >
            <generator class="com.MyCategoryPkGenerator"/>
        </id>

You then have to define the type MyCategoryPkType as a UserType that store CategoryPk and MyCategoryPkGenerator that generates new instances of CategoryPk.

We did that in our application but the type of the id is the same for all the classes. In you case, I think it will be too much work if you create two more classes for each domain object.