17 Sep 2013

Populating tables with method iterator

Sometimes it can be useful to provide the data collection for a table component by some custom method in the service layer. An example of this technique can be found here. In this case we use methodAction to invoke the method and methodIterator to represent method's return value as a data collection for the table.
Let's say in our EmployeesView view object we've got a method returning some secondary custom ViewObject's row set:
   public RowSet getManagers(){   
    RowSet rs = (RowSet) findByViewCriteria(getViewCriteria("ManagersCriteria"), -1,  
                              ViewObject.QUERY_MODE_SCAN_DATABASE_TABLES);  
    return rs;       
  }


In the PageDef file we've got methodAction invoking this method:
<methodAction id="getManagers" RequiresUpdateModel="true"
    Action="invokeMethod" MethodName="getManagers"
    IsViewObjectMethod="true"
    DataControl="AppModuleDataControl"
    InstanceName="data.AppModuleDataControl.EmployeesView"
    ReturnName="data.AppModuleDataControl.methodResults.getManagers_AppModuleDataControl_EmployeesView_getManagers_result"
    />


The methodIterator:
    <methodIterator Binds="getManagers.result"
                    DataControl="AppModuleDataControl" RangeSize="25"
                    id="getManagersIterator"/>
 
And the tree definition:
    <tree IterBinding="getManagersIterator" id="VEmployees1">
      <nodeDefinition DefName="com.cs.blog.appmethoditerator.model.EmployeesView"
                      Name="VEmployees10">
        <AttrNames>
          <Item Value="EmployeeId"/>
          <Item Value="FirstName"/>
          <Item Value="LastName"/>
        </AttrNames>
      </nodeDefinition>
    </tree>


The table which is based on this structure looks like this:


Everything seems to be fine. But, actually, it's not. If we try to sort our data in the table, there will be no any effect. The getManagers method is going to return new row set without any bothering about applied sort criteria. Actually the framework applies the sort criteria to the EmployeesView view object, but not to the row set, returning by the getManagers method. On the other hand, this secondary row set is populated by some internal helper view object, which is called finder view object. And this finder view object has no any idea about changed OrderBy clause. We can fix that overriding ViewObject's method createFinderVO:

  protected ViewObjectImpl createFinderVO(String suffix) 
  {
    ViewObjectImpl vo = super.createFinderVO(suffix);
    //Get OrderBy clause from the parent VO and set it up for the finder VO 
    vo.setOrderByClause(getOrderByClause());
    return vo;                                                           
  }


And now everything works really fine.

That's it!