Why are you storing the value in a session? What's your specific need that dicates a session variable must be used? When you select a tree item, you have access to it through the Selected Rows param of the service you used to populate your tree. Does each node relate to it's own unique mashup or are there multiple nodes that all use the same mashup? If the former, then you can modify your datashape to include a mashup attribute and then set that attribute to the corresponding mashup, set your tree "value" param to use the mashup column and then bind from the Selected Rows of your service to a navigate widget mashup property. You can cause the navigate widget to fire on a tree double click event or by using using a button widget.
For the latter scenario, use a lookup datatable that maps the tree nodes to the corresponding mashup. Query the datatable based on the selected node to get the mashup name. Again, bind a navigate widget to the Results param of the service you use to query your datatable. You trigger the navigate action the same way as described earlier--the tree double click event or using a button.
Hi Anind Dey as i understand what you are saying i think,
To the tree you must have given infotable or data from datatable so take the output result from Selected rows and and bind it to the Mashup name of Navigation Widget.
Note: the Name of the Mashup Should Same as the name taken as a output from the service.