Hi, I am very new to Hibernate and JPA. I am using Hibernate 3.3 with Hibernate annotation 3.4, and I tried to use JPA as much as I could unless the features are missing in JPA (such as CollectionId). I have been fighting with the following mapping problem for a while. I think this should be a basic mapping requirement, yet, I could not resolve it...

I have a Person entity table, mapping to a person table. Since a person might have multiple addresses, I want to map a collection of addresses to this Person by using CollectionOfElements annotation. However, each time when I retrieve the person object out, the collection of addresses are always empty (even with eager fetch), though the generated SQL looks fine to me..

This is my Person class:

@Entity
public class Person {

private long emplId;

private List<Address> addresses = new ArrayList<Address>();

@Id
public long getEmplId(){
return emplId;
}

@org.hibernate.annotations.CollectionOfElements (fetch=FetchType.EAGER)
@JoinTable(
name="ADDRESSES",
joinColumns = @JoinColumn(name="EMPL_ID")
)
@org.hibernate.annotations.CollectionId(
columns = @Column(name="ID"),
type = @org.hibernate.annotations.Type (type = "long"),
generator = "sequence")
public List<Address> getAddresses(){
return addresses;
}
// setters and other properties omitted here
}

Then, I have an embeddable Address class
@Embeddable
public class Address {

private Person person;
private String addressTypeCd;
private String addressLine;

@org.hibernate.annotations.Parent
public Person getPerson() {
return person;
}

public void setPerson(Person person) {
this.person = person;
}
}

The generated SQL is:

Hibernate: select person0_.EMPL_ID as EMPL1_5_0_, ......, addresses1_.EMPL_ID as EMPL1_2_, addresses1_.city as
city2_, addresses1_.TYPE_CD as TYPE12_2_,
from PEOPLE person0_ left outer join ADDRESSES address
es1_ on person0_.EMPL_ID=addresses1_.EMPL_ID where person0_.EMPL_ID=?

The SQL looks fine to me. However, when I tried to access person.getAddresses(), the list is empty. Could anyone point to me what the problem is here? I started off using lazy fetch type and doesn't set parent reference in my Address class, but it's not working, so I change the fetch type to eager and add parent reference in Address class. It's still not working:-( One moer thing is that in fact, my Person class is a root class for a hierarchical structure (inheritance type is table per concrete class), and when I tried to use the general Person type as parent in Address class, I got the complaint that it could not figure out the type of Person... hence, I tried to avoid to have the parent reference in my Address class... I think the mistake I made must be very obvious for an experienced Hibernate developers, and I appreciate very much for any insights you might have. Thanks!

I've figured out what's wrong. It's actually our database script data population problem, and has nothing to do with my mapping at all. After repopulate our testing data, I got the result back without problem. The parent reference is not necessary and I was able to retrieve the collection of value types with lazy loading. If I could remember to check with the database data again before assuming this a JPA mapping problem, it would save me a lot of time. Sorry about posting this problem...