Retrieving first item in collection - unindexed fromElement

peterz · **Joined:** Wed May 14, 2008 5:58 am **Posts:** 4

Hello there, I need to retrieve a property on the first item in a collection:

Code:

public class Order {
 @OneToMany(mappedBy="order", targetEntity=Item.class)
 private List<Item> items;

 // Getter and setter
}

public class Item {
 private Integer ID;
 @ManyToOne(targetEntity=Order.class)
 private Order order;
 private Integer code;

 // Getters and setters
}

I have tried:

Code:

executeHQLQuery("FROM Order AS order WHERE order.items[0].code = 5");

But I get the error:

Code:

org.springframework.orm.hibernate3.HibernateQueryException: unindexed fromElement before []

Any ideas? The join works fine when retrieving an Order normally.

Many thanks.

Cameron McKenzie · **Posted:** Wed May 14, 2008 9:55 am

So, you are looking for an Order with a particular code property - in this case the value of 5?

Wouldn't a slick use of the Criteria API make this a whole lot easier?

Code:

    Order o = new Order();
    o.setCode(5);
    Example example = Example.create(o);
    Session session = HibernateUtil.beginTransaction();
    Criteria criteria = session.createCriteria(Order.class);
    criteria.add(example);
    List results = criteria.list();
    HibernateUtil.commitTransaction();
    for (int i = 0; i<results.size(); i++) {
      System.out.println(results.get(i).toString());
   }

This example is taken from a Hibernate example tutorial from here:

http://www.hiberbook.com/HiberBookWeb/learn.jsp?tutorial=09howtousethecriteriaapi

Criteria queries are very efficient, and will alleviate many of your Hibernate Query Language headaches.

-Cameron McKenzie

peterz · **Joined:** Wed May 14, 2008 5:58 am **Posts:** 4

Thank you :) Yes, that is easier - I just started with HQL and didn't want to let go! I can't find many references to the error on the web, so I would still be interested in knowing the problem...

peterz · **Joined:** Wed May 14, 2008 5:58 am **Posts:** 4

Sorry, on second glance this doesn't solve the problem at all. I am looking for a property called "code" on the FIRST Item in an Order's "items" list. It seems there's a problem with addressing the index 0 in the way that I have done it....

Thanks!

salvin18 · **Joined:** Tue Jan 13, 2009 4:32 am **Posts:** 3

I am a newbie to hibernate too

here is a schema:

Code:

public class Person {
   String firstName;
   String middleName;
   String lastName;
   int Id;

   Set setEmails=new HashSet(); //Bad naming convention indeed
}

This is the query that i am trying to execute:

Code:

from Person p where p.setEmails[0]='a@b.com'

I am getting the same exception. Please Help

I had referred to
http://www.hibernate.org/hib_docs/refer ... sions.html
for the above syntax

My exception:

Code:

Exception in thread "main" org.hibernate.QueryException: unindexed fromElement before []: p.setEmails [from simpledemo.Person p where p.setEmails[0]='a@b.com']

nordborg · **Posted:** Tue Jan 13, 2009 5:00 am

The collection needs to be an array or list if you want to use indexes. Eg. you need to specify an @IndexColumn in your annotations. See http://www.hibernate.org/hib_docs/annot ... -extratype for more information

salvin18 · **Joined:** Tue Jan 13, 2009 4:32 am **Posts:** 3

thanks for the prompt replay.

its good if its possible to use array/list

Is there another way to access using Sets ?