2 Select Box`s on one page, second needs to load dynamically

[Derick Potgieter]

Hi,

I`m struggling with an problem on one of my pages, to do with selects.

I need to display a list of countries around the world in a drop down, then when the user selects the first country
I need to populate the second drop down with the towns under that country.
All this data comes from my DB2 database.

This has to be on one page, as I only need the ID from the second drop down to write back to my database.
Now I don�t have a problem to populate the first select, but how do you handle the second if I needs to be dynamically
Loaded from the database?

Thanks, any help will be appreciated?

Rgds
Derick

[Eric Pascarello]

You are going to need to do a post back on the server with an onchange event on the server. Using jsp?

Eric

[Derick Potgieter]

Yes, sorry this buggles my mind a bit. Do you mabe have some code that could help me??

thanks

[Eric Pascarello]

I am assuming jsp?

http://forum.java.sun.com/thread.jspa?threadID=594047&messageID=3121257

Eric

[Derick Potgieter]

Hi, thanks

I am using JSP`s, with struts.

I cant believe that it takes that much effort jsut to get the second select working.

Is there no other way to go though this process using some of struts`s features??

Thanks
Derick

[Eugene Lucash]

You can write a some simple solution.
Imagine a real code instead of pseudo-pseudo-java-code

In POJO's

class Option {
int id; //do it with setter and getter
String name; //do it with setter and getter
}
 
class SomeSelectDao {
static List getOptions(Connection c, String selectQuery) {
.... // error handling ommited
ResultSet rs = ... //execute selectQuery
List list = new ArrayList();
while(rs.next()) list.add(mapRow(rs));
return list;
}
static Option mapRow(ResultSet rs) throws Exception {
Option o = new Option();
o.id = rs.getInt(1); //column 'id', do it with setter 
o.name = rs.getString(2); //column 'name', do it with setter 
return o;
}
}

In Action

......
......
List list;
list = SomeSelectDao.getOptions(connection,
 "SELECT id, name FROM Countries");
request.setAttribute("countries", list);
list = SomeSelectDao.getOptions(connection,
  "SELECT id, name FROM Cities WHERE"+
" cid=" + countryId); //get countryId from countries' select box
request.setAttribute("cities", list);
 
...

In JSP

......
<html:select property="countryId" onchange="this.form.submit()">
<html:options collection="countries" property="id" labelProperty="name"/>
</html:select>
.......
<html:select property="cityId">
<html:options collection="cities" property="id" labelProperty="name"/>
</html:select>
......

I hope this give you some insight

[ February 19, 2005: Message edited by: Eugene Lucash ]

[ February 19, 2005: Message edited by: Eugene Lucash ]

[ February 19, 2005: Message edited by: Eugene Lucash ]

[ February 19, 2005: Message edited by: Eugene Lucash ]

[ February 19, 2005: Message edited by: Eugene Lucash ]
[ February 19, 2005: Message edited by: Eugene Lucash ]

[Eric Pascarello]

There is a JavaScript solution if you want to avoid the post back. What you would have to do is write all of the possible items in JavaScript arrays. If you want this, you can search on google for JavaScript Double combo and you should find some results.

Eric