<c:forEach> iterating through multiple collections in parallel
Hi there,
I have two arrayLists, one contains a list of ids and the other contains a list of names. The ids and the names in a particular position in their arrayList correspond so that the id in position one corresponds to the name in position one.
I want to use <c:forEach> to iterate through these arraylists so that the names and corresponding Ids are printed together. Is this possible?
For example, I want to use the id as part of a url and the name to be what the user clicks on.
<c:forEach var="k" items="${inbox.id}">
<a href="ProfileServlet?id=${k}">${inbox.name[x]}</a>,
</c:forEach>
Is there a way to perhaps increment a variable, x in ${inbox.name[x]}
Hope Im making myself clear! Thanks!
Better, use Hashtable (key, value pairs)
Hashtable table = new Hashtable();
ArrayList names = new ArrayList();
.....
names = nameBO.getNames(.,.);
.....
table.put(id, names); //populate the Hashtable
to fetch:
if (table != null) {
Set set= table.keySet () ;
Iterator iter = set.iterator () ;
while ( iter.hasNext () )
{
String id = (String)iter.next();
ArrayList nameData = (ArrayList)table.get(data);
for(int j = 0; j < nameData.size(); j++)
{
String name = nameData.get[j].toString();
}
}
}
Thanks for the reply, actually I simiplified my problem to make it easier to explain. What happens if I want to obtain values from 6 collections where values correspond? A hashmap only takes a key and a value. Therefore would it work?
almost anything is possible. Whether it is advisable is another matter.
The varStatus attribute of the c:forEach loop exposes a index/counter for you to use.
<c:forEach var="k" items="${inbox.id}" varStatus="status">
<a href="ProfileServlet?id=${k}">${inbox.name[status.index]}</a>
</c:forEach>
However I think you could use a better datastructure than parallel lists.
I would have an object "Inbox" which had attributes id, name ... and then iterate through a list of them.
public class Inbox{
private int id;
private String name;
// getter/setter methods for id/name
}
You then expose a list of Inbox objects to your jsp page (one list as opposed to 6)
<c:forEach var="inbox" items="${myListOfInboxes}">
<a href="ProfileServlet?id=${inbox.id}">${inbox.name}</a>,
</c:forEach>
And using the c:url tag just for kicks :-)
<c:forEach var="inbox" items="${myListOfInboxes}">
<c:url value="ProfileServlet" var="theURL">
<c:param name="id" value=${inbox.id}">
</curl>
<a href="${theURL}">${inbox.name}</a>,
</c:forEach>
[nobr]Thanks for the reply, what you have said makes a lot of sense! :D
I have opted for the option you recommended and I am now accessing an arrayList of inbox beans. However, when I do the c:forEach, for some reason, rather than displaying the contents of each bean it is displaying the same bean multiple times!
<c:forEach var="inbox" items="${homeInboxList}">
<a href="ProfileServlet?action=profile&profileid=${inbox.fromUserId}"><img src="${inbox.imagePath}"/></a>
<a href="InboxServlet?action=message&messageid=${inbox.messageId}"> ${inbox.firstname} ${inbox.lastname}</a> ${inbox.date}<br/>
</c:forEach>
It retrieves te correct number of beans but it seems to repeat the same bean.
Any ideas what I am doing wrong? Maybe something obvious?[/nobr]
Dont worry! Problem solved.
The problem was in my servlet, i wasn't initiating a new
bean for each row of my result set. I kept using the same bean and consequently I was overwriting the previous rows. New it had to be a silly mistake.
Thanks so much for your help! :D
