Fetching more than one row from a table after selecting one value from the dropdown

Question

Hi Experts,
How can we fetch more than one row from a table after selecting one value from the dropdown.
The scenario is that I have some entries in the dropdown like below
  A               B               C        
11256          VID          911256  
11256          VID          811256
11256          SONY      11256
The 'B' values are there in the dropdown. I have removed the duplicate entries from the dropdown so now the dropdownlist has only two values.for eg- 'VID' and'SONY'. So now, after selecting 'VID' from the dropdown I should get all the 'C' values. After this the "C' values are to be passed to other methods to fetch some data from other tables.
Request your help on this.
Thanks,
Preeetam Narkhede.

Answer 1

Hi Preetam!
I hope I understand your request proberly, since this is more about Java and less about WebDynpro, but if I'm wrong, just follow up on this.
Supposed you have some collection of your original table data stored in variable "origin". Populate a Hashtable using the values from column "B" (let's assume it's Strings) as keys and an ArrayList of whatever "C" is (let's assume String instances, too) as value (there's a lot of ways to iterate over whatever your datasource is, and since we do not know what your datasource is, maybe you'll have to follow another approach to get b and c vaues,but the principle should remain the same):
// Declare a private variable for your Data at the appropriate place in your code
private Hashtable temp = new Hashtable<String, ArrayList<String>>();
// Then, in the method you use to retrieve backend data and populate the dropdown,
// populate the Hashtable, too
Iterator<TableData> a = origin.iterator();
while (a.hasNext()) {
     TableData current = a.next();
     String b = current.getB();
     String c = current.getC();
     ArrayList<String> values = this.temp.get(b);
     if (values == null) {
          values = new ArrayList<String>();
     values.add(c);
     this.temp.put(b, values);
So after this, you'll have a Hashtable with the B values als keys and collections of C values of this particular B as value:
VID --> (911256, 811256)
SONY --> (11256)
Use
temp.keySet()
to populate your dropdown.
After the user selects an entry from the dropdown (let's say stored in variable selectedB), you will be able to retrieve the collection of c's from your Hashtable
// In the metod you handle the selection event with, get the c value collection
//and use it to select from your other table
ArrayList<String> selectedCs = this.temp.get(selectedB);
// now iterate over the selectedCs items and use each of these
//to continue retrieving whatever data you need...
for (String oneC : selectedCs) {
     // Select Data from backend using oneC in the where-Clause or whatever...
Hope that helps
Michael