database list contains wrong objects - xwiki

Question

Goal:
To create a database with documentation about drivers. The idea is to create both vendor and protocol entries, and to link them, as follows: Inside the protocol creation form, I would like to select which vendor supports this protocol.
Approach:
I used the Create your own! button to create the following 2 Applications:
Vendors
Protocols
Inside the protocol creation page I've put a Database List field. With the following properties:
Name = vendors
Display type = select
Multiple select = false
hibernate query : I left this field blank.
xwiki class name = VendorsCode.VendorsClass
ID field name = doc.name
value field name : I left this field blank.
Problem:
To my surprise this works, but not entirely. When I open the form to add a protocol, in the vendor dropdown list there are now not only vendors but also a couple of other objects such as : "Blog.BlogIntroduction". Obviously I don't want that in the list. Why is it in there, and how can I get it out ?
I tried to add the value doc.name in the value field name box as well. But that actually only makes it worse. Now the list only contains "Blog.BlogIntroduction".
Notice that this is a clean fresh installation of xwiki. There's nothing special in this database.

Answer 1

What is going on here?
What you see is the default value for the select item in the Database List, as it is stored in the template page for "Protocol" objects.
A new Database List is initialized to show a list of blog posts, by having a default value of Blog.BlogPostClass for the "XWiki Class Name". (You can try this by creating a new Database List field in step 2 and open the edit view that field; just delete it after you are done.) For a fresh installed wiki there are two blog posts: the "blog page template" in Blog.BlogPageTemplate and the blog intro post in Blog.BlogIntroduction. Exactly these two items are shown initially.
After you fill in the value of your class in the "XWiki Class name" field, XWiki has a chance to find the actual list of possible values.
However it keeps the selected "default value" from the first attempt around (even though it makes no sense).
This looks like a bug to me, at least from a user experience.
How to fix it
First Step: The reason why your list only contains the bogus "default value" might be that the class you have given does not exist.
From what I see in the screenshot the class name looks ok for me, but then this field is not tolerant to any kind of typos, even something like a space before the class name. If the name does not fit exactly, it gives a (nearly) empty list.
If you cannot get it working with the class name and want to go the HQL route instead, use for the HQL field
, BaseObject as obj where doc.fullName = obj.name
and obj.className = 'VendorCode.VendorClass'
and doc.fullName != 'VendorCode.VendorTemplate'
and doc.fullName both as id and value field. This has the additional benefit that the template vendor is not available in the drop down, only the "real" objects.
After you managed to fix the name of the class, you should see a list of all vendor objects (including the VendorCode.VendorTemplate, unless you went the HQL route), and the remaining bogus default value. Now you can continue to the next step:
Second Step: if you managed to fix the class name, you will see your vendors in the drop down beside the default value; now it is time to get rid of the bogus default value. For this go to the template object of the application; e.g.
follow the "Edit Application" link on the start page of the "Protocol" application
then look at the box with the three checkboxes below the field definitions; the uppermost of the checkboxes says "Update class template"
this part contains a link to something called "ProtocolTemplate".
click the link and you end up at the template page
on the template page, click on edit and choose some other value from the drop down of vendors, and then click save.
The "BlogSomething" value should be gone now from the selection of vendors.
Optional step (not answering the quesion, but might be of interest anyway)
If you prefer to have no value at all preselected in the template, you need a few more steps:
in the application edit, edit the field and choose "multiple select" and display type "checkbox"
go to "next step" in the editor, then back to field edit with "previous step"
uncheck the checkbox beside the selected vendor entry, then open the field editor and set "display type" back to checkbox and unset the "multiple select" checkbox.
go the "next step" and "finish"
Afterwards if you create a new "protocol" entry, this is has an empty "vendor" preselected.