I'm feel like I'm close to solving, but keep getting "derefenced" error:

Error:
dereferenced: projectm1_.comp_id.user.username.elements [select distinct projec
t from com.supergloo.database.bean.Projects projects inner join projects.project
members pm where 'x' in elements(pm.comp_id.user.username)]

when trying:

1) session.find("select distinct project from Projects projects inner join projects.projectmembers pm where 'x' in elements(pm.comp_id.user.username)").iterator();

or

2) session.find("select distinct project from Projects projects inner join projects.projectmembers pm where elements(pm.comp_id.user.username) = 'x'").iterator();

Mappings:
<hibernate-mapping>
<class name="com.supergloo.database.bean.Projects" table="projects">

<id name="pid" type="int" column="pid">
<generator class="assigned" />
</id>

<property
name="projectname"
type="java.lang.String"
column="projectname"
length="50"
/>
<property
name="status"
type="java.lang.String"
column="status"
length="50"
/>

... bunch of property elements....

<property
name="accesslevel"
type="java.lang.String"
column="accesslevel"
length="25"
/>

<!-- associations -->
<!-- bi-directional one-to-many association to Projectmembers -->
<set name="projectmembers" lazy="true" inverse="true">
<key>
<column name="pid" />
</key>
<one-to-many class="com.supergloo.database.bean.Projectmembers"/>
</set>

</class>
</hibernate-mapping>

<hibernate-mapping>

<class
name="com.supergloo.database.bean.Projectmembers"
table="projectmembers"
>

<composite-id name="comp_id" class="com.supergloo.database.bean.ProjectmembersPK">
<!-- bi-directional many-to-one association to Projects -->
<key-many-to-one
name="project"
class="com.supergloo.database.bean.Projects">
<column name="pid" />
</key-many-to-one>
<!-- bi-directional many-to-one association to Users -->
<key-many-to-one
name="user"
class="com.supergloo.database.bean.Users"
>
<column name="username" />
</key-many-to-one>
</composite-id>

</class>
</hibernate-mapping>

Using Hibernate 2.1, Postgres 7.3.4

Am I heading in the right direction?

Does this works ?

Thank you. I tried that before posting, but kept getting java.lang.OutOfMemory errors, so I thought I was doing something wrong. Just to double check, I tried again and still receive OoMemory

do you implements equals and hashCode in your comp_id class. This is required, have a look at the ref guide (searching for equals)

I think so. I have the following in the com.supergloo.database.bean.ProjectmembersPK class:

public boolean equals(Object other) {
if ( !(other instanceof ProjectmembersPK) ) return false;
ProjectmembersPK castOther = (ProjectmembersPK) other;
return new EqualsBuilder()
.append(this.getProject(), castOther.getProject())
.append(this.getUser(), castOther.getUser())
.isEquals();
}

public int hashCode() {
return new HashCodeBuilder()
.append(getProject())
.append(getUser())
.toHashCode();
}

This was generated from ...hbm2java.CodeGenerator in an Ant task.

And Projectmembers equals and hashCode refers to the PK ones ?

Perhaps related? I also receive an OutofMemory when:

Projects proj = (Projects)session.load(Projects.class, new Integer(id));

Windows 2000 server, over 500MB of RAM, Sun JVM 1.4.2

Here's from the Projectmembers:

public boolean equals(Object other) {
if ( !(other instanceof Projectmembers) ) return false;
Projectmembers castOther = (Projectmembers) other;
return new EqualsBuilder()
.append(this.getComp_id(), castOther.getComp_id())
.isEquals();
}

public int hashCode() {
return new HashCodeBuilder()
.append(getComp_id())
.toHashCode();
}

Let's focus on that.
If you comment the set one-to-many, do you get the OutOfMemory when loading it. Guess not.
Do you see something in the log?

I really suspect a wrong equals implementation, maybe in user

I really appreciate your help. Thank you. I was thinking of the same thing- concentrate on this:

Projects proj = (Projects)session.load(Projects.class, new Integer(id));

So, since last post this is what I've done:

Removed the foreign key to Users in the Projectmembers table and updated the Projectmembers.hbm.xml from:

<composite-id name="comp_id" class="com.supergloo.database.bean.ProjectmembersPK">
<!-- bi-directional many-to-one association to Projects -->
<key-many-to-one name="project"
class="com.supergloo.database.bean.Projects">
<column name="pid" />
</key-many-to-one>
<!-- bi-directional many-to-one association to Users -->
<key-many-to-one name="user"
class="com.supergloo.database.bean.Users">
<column name="username" />
</key-many-to-one>
</composite-id>

To:

<composite-id name="comp_id" class="com.supergloo.database.bean.ProjectmembersPK">
<key-property
name="username"
column="username"
type="java.lang.String"
length="50"
/>
<!-- bi-directional many-to-one association to Projects -->
<key-many-to-one
name="project"
class="com.supergloo.database.bean.Projects"
>
<column name="pid" />
</key-many-to-one>
</composite-id>


Essentially, changing key-many-to-one to key-property. And now, I'm able to run both session.load(..) and session.find() with expected results and without OutofMemory! That's good progress.

So, I'm just a beginner and do not know anything, but could there be an issue with having multiple (in my case, 2) key-many-to-one elements in a composite-id?

I don't know, I'm not fond of composite-id and key-many-to-one is worse to me ;-(

Loading a user give you OutOfMemory ? I still believe User is somehow broken