Is it possible to use IMAP + paging?

Question

Hi, I have a Requirement to make an IMAP client as a Web application

I achieved the functionality of Sorting as:

   //userFolder is an Object of IMAPFolder
   Message[] messages = userFolder.getMessages();

   Arrays.sort(messages, new Comparator<Message>()
    {
        public int compare(Message message1, Message message2)
        {
            int returnValue = 0;
            try
            {
                if (sortCriteria == SORT_SENT_DATE)
                {
                    returnValue = message1.getSentDate().compareTo(message2.getSentDate());
                }
            } catch (Exception e)
            {
                System.out.println(e.getMessage());
                e.printStackTrace();
            }

            if (sortType == SORT_TYPE_DESCENDING)
            {
                returnValue = -returnValue;
            }

            return returnValue;
        }
    });

The code snippet is not complete , its just brief SORT_SENT_DATE,SORT_TYPE_DESCENDING are my own constants.

Actually This solution is working fine, but it fails in logic for paging Being a Web based application, i cant expect server to load all messages for every user and sort them (We do have situations >1000 Simultaneous users with mail boxes having > 1000 messages each )

It also does not make sense for the web server to load all, sort them, return just a small part (say 1-20), and on the next request, again load all sort them and return (21-40). Caching possible, but whts the gaurantee user would actually make a request ?

I heard there is a class called FetchProfile, can that help me here ? (I guess it would still load all messages but just the information thats required) Is there any other way to achieve this ?

I need a solution that could also work in Search operation (searching with paging), I have built an archietecture to create a SearchTerm but here too i would require paging.

for ref, i have asked this same Question at : http://www.coderanch.com/t/461408/Other-JSE-JEE-APIs/java/it-possible-use-IMAP-paging

Answer 1

You would need a server with the SORT extension and even that may not be enough. Then you issue SORT on the specific mailbox and FETCH only those message numbers that fall into your view.

Update based on comments:

For servers where the SORT extension is not available the next best thing is to FETCH header field representing the sort key for all items (eg. FETCH 1:* BODY[HEADER.FIELDS(SUBJECT)] for subject or FETCH 1:* BODY[HEADER.FIELDS(DATA)] for sent date), then sort based on the key. You will get a list of sorted message number this way, which should be equivalent to what the SORT command would return.

If server side cache is allowed then the best way is to keep cache of envelopes (in the IMAP ENVELOPE sense) and then update it using the techniques described in RFC 4549. It's easy to sort and page given this cache.

There are two IMAP APIs on Java - the official JavaMail API and Risoretto. Risoretto is more low-level and should allow to implement anything described above, JavaMail may be able to do so as well, but I don't have much experience with it.