How do I create linked LOVs in a JSP

Question

We are attempting to create a list of values (LOV) for a group of categories on a jsp page. We would like the LOV to be populated with the category names. Next to the category LOV we would like to have a link “get subcategories” that when clicked would return to the same jsp page, set the value of the LOV to the category selected, and populate a second LOV with sub-category names for the selected category.
We have created an sql-only View Object (VO) for the categories and linked it to an sql-only VO for the subcategories (in a master-detail relationship) and added the VOs to an app module. We have tested the link between the two VOs with successful results.
We would like to know how to create a linked pair of LOVs on a jsp page. Any help on this matter would be greatly appreciated.

Answer 1

Les,
If I understand correctly, you can do this fairly simply.
First create datasources:
<jbo:DataSource name="dsCategories" ...
<jbo:DataSource name="dsSubCategories" ...
<% // add a where clause to SubCategories based on the parameter "CategoryNumber"
String categoryNumber = params.getParameter("CategoryNumber");
// Make sure to default to something if the parameter is null or you'll get an error
if (categoryNumber == null)
categoryNumber = "1";
dsSubCategories.getRowSet().setWhereClauseParam(0, categoryNumber);
// execute the query on dsSubCategories to ensure that the where clause reflects on this page
dsSubCategories.getRowSet().executeQuery();
Create a form with your drop down lists.
1. I would create a <form> that posts to the same page.
2. Add a <jbo:FormEvent> tag with a custom event name like "getSubcategories".
3. Create a LOV that isn't connected to the database:
<jbo:InputSelect multiple="false" displaydatasource="dsCategories" displaydataitem="CategoryName" displayvaluedataitem="CategoryNumber" ></jbo:InputSelect>
4. Create a second LOV that also isn't connected to a datasource. It would look like this:
<jbo:InputSelect multiple="false" displaydatasource="dsSubCategories" displaydataitem="SubCategoryName" displayvaluedataitem="SubCategoryNumber" ></jbo:InputSelect>
5. Add a submit button
That should work. Some things to note:
1. This probably won't track your previously selected options. I don't know if you can do that with this interface.
2. I'd add some javascript to postback when a new list item is selected.
Based on these points I would code the select list by hand like this:
<select name="CategoryNumber" size="1" onchange="this.form.submit()">
<% String curCatNumber="";
String CatNumber = params.getParameter("CategoryNumber");
if (CatNumber == null)
CatNumber = "1";
<jbo:RowsetIterate datasource="dsCategories" >
<jbo:Row id="rowCategory" datasource="dsCategories" action="active" >
<% curCatNumber = ((oracle.jbo.domain.Number)rowCategory.getAttribute("Category")).toString();%>
<option value="<%=curParlimentId%>"
<% if (CatNumber.equals(curCatNumber)) { %>selected<% } %>>
<jbo:ShowValue datasource="dsCategories" dataitem="CategoryName" ></jbo:ShowValue>
</option>
</jbo:Row>
</jbo:RowsetIterate>
</select>
The second would be similar.
Hope this answered your question!
~Rob Lundeen