Flex with Java - DB data access

Question

Hello, folks,
I am developing a Java application and realized that I need
some advice. My application is simple:
I have a MSSQL server, tomcat 5.5 ,flex data services.
In my application , i have two combo boxes.. country, town..
i have populated the country combobox with the values from
DB(country table) obtained using the fill(List ListArgs) in
Assembler Class.
Now, based on the country selected in have to populate my
town combobox from (town table)
How can i populate the town combobox from the DB based on the
country code?
Is there any function to pass the selected index and populate
the town combo box..????
My code is as below:
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
layout="absolute" >
<mx:DataService id="ds" destination="quick-search-country"
autoCommit="false" autoSyncEnabled="false"/>
<mx:DataService id="tds" destination="quick-search-town"
autoCommit="false" autoSyncEnabled="false"/>
<mx:ArrayCollection id="cntry_list"/>
<mx:ArrayCollection id="town_list"/>
mx:Panel layout="absolute" backgroundColor="#c6daf5"
verticalCenter="0" horizontalCenter="0">
<mx:Form id="SearchForm">
<mx:TabNavigator >
<mx:Canvas label="Hotel" width="339" height="234"
backgroundColor="#ffffff">
<mx:Label x="10" y="91" text="Country :" alpha="0.12"
/>
<mx:ComboBox x="93" y="89" fontSize="10" id="Country"
dataProvider="{cntry_list}"
labelField="countryName"
creationComplete="ds.fill(cntry_list)"
change="tds.getItem(Country.selectedItem)" prompt="United
Kingdom" >
</mx:ComboBox>
<mx:Label x="10" y="126" text="Town / City :"
fontFamily="Georgia" alpha="0.12"/>
<mx:ComboBox id="town" x="94" y="124" fontSize="10"
dataProvider="{town_list}"
labelField="townName" prompt="London WC1" >
</mx:ComboBox>
</mx:Canvas>
</mx:TabNavigator>
</mx:Form>
</mx:Panel>
</mx:Application>
this is my main.mxml . I have CountryAssembler to fill the
country combo and a DAO class . Have a Town assembler..
Please advice me on how to populate the town combo based on
country selected from the DB...
I am really stuck up... and also dont have any documentation
on Flex data services with Java support..
please give me some suggestions on this.
Thanks in Advance,
Ambili

Answer 1

Hi Mete,
Thanks for ur reply , Mete. Your reply helped me a lot. Am
using FDS 2.0.
I have a doubt in combo box area itself.
I have two tables by name country_list and town_list
country_list consists of identity column , country_name and
country_code
town_list has identity column, country_code, town_code and
town_name
Normally while we use combobox in jsp, we have key value
pairs for combo box..
For eg:- if we have a Country combo , we have the country
name(United States) as text displayed and its country code (US) as
key.
So if i select the United States , i will be returned with
the value 'US' so that i can use it in query directly as
Select town_name, town_code from town_list where country_code
='US'
But while using flex , am not able to retieve the
country_code from country combo. its only returning the text and
the id.
Here am forced to write a nested query as follows
Select town_name, town_code from town_list where country_code
=( Select country_code from country_list where country_name='United
States')
Is there any way to get the country_code as key while i
select the country from country combo .
And also how to keep 'United States' as selected during the
intial load of the page.
<mx:ArrayCollection id="cntry_list"/>
<mx:ComboBox x="93" y="89" fontSize="10" id="Country"
dataProvider="{cntry_list}"
labelField="countryName"
creationComplete="ds.fill(cntry_list)"
prompt="Select Country" />
please give me some suggestions on this.
Thanks in Advance,
Ambili