Re: OFF-TOPIC - Paging Results

[he...@teradyne.com]

There is a section on this in the Bitter EJB book that pretty good. 

looking at pagination in general(not specific to tags ).
Problem with scrollable resultsets is that some implementations (don't 
know which) it actually loads each row as you scroll through it.
So if you go to row 50,  it scrolls and can caches rows (0-49) in memory. 
For small result sets this would be fine, but when you get a large numbers 
of rows you get into trouble quickly.

It basically comes down to your requirements. 
Do you support large number of clients running queries with relativly 
small results or few clients but huge results. Or both

If you go the page-by-page iterator way from sun blueprints (aka 
ValueListHandler) you could abstract out the fact that it either caches it 
all 
or uses DB vendor specific extension to load results from middle of result 
set(different DAO for vendors for example). 
Then based on your use cases(large number of users or large queries), let 
it be configurable which one it uses. 

There's plenty of discussions on this at theserverside.com. Also check out 
javaranch.com. 
Search for "page-py-page iterator" or for 
"ValueListHandler" 


-Henrik






"Adolfo Miguelez" <pe...@hotmail.com>
03/30/04 01:44 PM
Please respond to "Struts Users Mailing List"

 
        To:     user@struts.apache.org
        cc: 
        Subject:        Re: OFF-TOPIC - Paging Results


A question that I wondered for long. AFAIK, there are 2 paging policies:

- paging in app server memory, in session scope to enable paging in 
clustered environments, or

- paging in dababase, using scrollable resulsets or related.

I guess, paging in app server, can overload server memory if query results 

are long, so database paging should be better, in such a cases. However, I 

do not know if state of arts in database paging is technologically ready.

I would appreciate comments further on this first impressions.

Regards,

Adolfo.







>From: Craig McClanahan <cr...@apache.org>
>Reply-To: "Struts Users Mailing List" <us...@struts.apache.org>
>To: Struts Users Mailing List <us...@struts.apache.org>
>CC: "'Struts Users Mailing List'" <st...@jakarta.apache.org>
>Subject: Re: OFF-TOPIC - Paging Results
>Date: Tue, 30 Mar 2004 10:01:07 -0800
>
>Joao Batistella wrote:
>
>>Hello!
>>
>>Sorry for the off-topic message.
>>
>>I would like to know if you recommend any good component for paging 
>>results
>>and presenting it in a JSP page. I'm using struts, so if you know a
>>component that integrates well with struts, that's perfect.
>>
>>Thanks for your help.
>>
>>
>>
>For working directly with Struts, Matt Raible's display tag is quite 
>popular.
>
>  http://displaytag.sourceforge.net
>
>If you are using the JavaServer Faces integration library with Struts, 
the 
>standard <h:dataTable> component handles paging quite nicely.  In 
addition, 
>it lets you do input fields in the table, not just output.
>
>  http://java.sun.com/j2ee/javaserverfaces/
>  http://cvs.apache.org/builds/jakarta-struts/nightly/struts-faces/
>
>Craig
>
>
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