[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-879) Enable joining the same association twice with Criteria

[Bernhard Hablesreiter (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=36025#action_36025 ] 

Bernhard Hablesreiter commented on HHH-879:
-------------------------------------------

I came across this issue a while ago and ended up writing a sort of "wrapper" around the criteria, especially the associations.

The problem usually appears when you have some dynamic query builder which adds the association-paths to the criteria more than once.
A simple approach to avoid this problem (and quite easy to implement) could be the following:

- Create a data-structure (this must be some kind of tree) which holds an association path, a list of child-nodes and a list of criterions/order/etc.
- Add your criterions/orders/etc. to the wrapper object
- Create the criteria using your wrapper object: 
  This method must be recursive. Using this approach you should only create the sub-criterias once (calling criteria.createCriteria(associationPath)) and then add the list of criterions/orders/projections or whatever, coming from the wrapper.

The tree-structure could look like this:
root
 +association1
  -criterion1
  -criterion2
 +association2
  -criterion1
  -criterion2
   +subassociation1
    -criterion1
    -criterion2

This structure is required for fetching associations over multiple hierarchies. Each node can have child-nodes and lists of criterions/orders/etc.

I think this is quite easy to implement and should work in most cases.

> Enable joining the same association twice with Criteria
> -------------------------------------------------------
>
>                 Key: HHH-879
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-879
>             Project: Hibernate Core
>          Issue Type: Improvement
>          Components: core
>            Reporter: Vladimir Bayanov
>
> Make double joining the same association with Criteria.createCriteria possible. See: http://forum.hibernate.org/viewtopic.php?t=931249

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