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 Post subject: trouble updating a many-to-many relationship via HQL
PostPosted: Thu Jun 14, 2012 8:48 pm 
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Joined: Thu Jun 14, 2012 8:42 pm
Posts: 2
I'm really stuck on something that seems like it should be easy. I have a Spring MVC webapp using Hibernate version 3.6.6. I have two objects - "ProjectUser" and "Project" - with a many-to-many relationship described in the database by the tables "users, "projects", and "projects_users." I have a portion of my app where I want to update the users in a project without updating any other fields in the "projects" table (it's a big table with lots of fields), so the easiest thing seemed to be to just write a separate method in my DAO and call the HQL directly. Here's the relevant portion of the "projects" class:

Code:
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "projects_users", joinColumns = @JoinColumn(name = "project_id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
private Set<ProjectUser> projectUsers ;


Everything works just fine on a select and also works if I pass along a full Project object and just call "session.saveOrUpdate(project)." However, my HQL to just update the users clearly has problems. Here's what I'm executing now:

Code:
Query query = getSession().createQuery("update Project set projectUsers = :projectUsers where id = :projectID ");
query.setParameter("projectUsers", project.getProjectUsers());
query.setParameter("projectID", project.getId());
int result = query.executeUpdate();


When I run this, I get a SQLGrammarException that reads "no value specified for parameter 2." It looks like I have a syntax error when I'm passing through the Set of ProjectUsers (if I run this same code on another field that does not involve a join it all works fine), but I can't figure out what to change to make this work. Any help would be appreciated.

Thanks,
Alex


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 Post subject: Re: trouble updating a many-to-many relationship via HQL
PostPosted: Fri Jun 15, 2012 2:25 am 
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Expert

Joined: Wed Mar 03, 2004 6:35 am
Posts: 1240
Location: Lund, Sweden
It's not possible to update collections with HQL. I think you'll have to use native SQL and work directly with the project_users table.


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