Datascroller and true pagination

[francof]

Hi

I am desperate here, I have been stuck on this for the last 2 weeks - I have time to kill right now but this is killing me :(

I did some custom changes with seam-gen to create an template with Richfaces datascroller for every list page. The problem I discovered later was that the datascroller was not really doing a true pagination and firing the entire query for every "next" page. Very costly, not something I would ever put in production and have a good night's sleep.

I am a newbie to Seam/Hibernate/Richfaces but not new to J2EE stuff.

This was perhaps a challenge I am not ready for yet. But I decided to give it a shot. I started looking at using a custom SerializableDataModel and found these many helpful posts on this topic.

http://www.seamframework.org/docDisplay_d.seam
http://eclecticprogrammer.com/2008/06/25/sorting-and-paginating-in-the-database-with-richfaces/


I used the approach documented in the latter post. Worked very well, with sorting too. But I had to be put my the datamodel in session scope for it to work.

I then encountered another issue - after a new search, the datascroller would not get reset. Let's say my first search gave me 20 rows and I had 10 rows per page, that would be 2 pages. when I did a new search resulting in either no data or 1 page of data, I would still see 2 pages.

Then I followed this
http://jboss.com/index.html?module=bb&op=viewtopic&t=127277

and bound my datascroller to my data table.

@Name("burstDataModel")
@Scope(ScopeType.SESSION)
public class BurstDataModel extends SerializableDataModel {
---
---

 @In(required=false)
 private BaseUIDatascroller datascrollerUI = null;
---
---
 public void search () {
 update();

 datascrollerUI.getDatascroller().getDataTable().setFirst(0);
 }


}

Search action would then call search method on datamodel above. Still no luck, the datascroller does not reset as expected.

The richfaces developers have put up a nice example how to do pagination using the extended data model. But it is in no way complete.

Then there are the critics of using the datascroller at all.
http://jboss.com/index.html?module=bb&op=viewtopic&t=139916
http://www.seamframework.org/Community/TroublesToUseDatascrollerAndExtendedDataModel

I implemented the Facelets tag in the 2nd post and it works great!

Then this guy shows how to reset the UIData in the model
http://solutionsfit.com/blog/2007/11/13/solution-using-seam-to-pagination-issue-with-jsf-on-datamodel-updates/

I did not try it, too raw for this stuff.


Richfaces developers:

Can you answer these questions ?
--------------------------------------------------------------------------------
Can the datascroller along with an extended model support true pagination ?
What scope should this model lie in ? -
session ? - overkill conversation - when should you start/stop the conversation ?
What scope should the data provider be in ?
How do you sync the datascroller to the data in the extended model ?
Is it not possible to have true paging built into the control itself ?
--------------------------------------------------------------------------------


I do not give up easily, but frankly I think I may have to concede defeat here!


Is there anyone who can post a complete working example for newbies ?


Thanks
Franco

[francof]

Sorry to bump this up.

Can anyone share their experience with the datascroller component.

Thanks,
Franco

[daniel.soneira]

In RichFaces 3.1.6 / 3.2.1 the datascroller should automatically reset to the first page if the model changes.

Which version are you using?

[francof]

I am using version 3.2.1

Perhaps the key then for me is understanding the sequence of steps when a new search is executed. In my code, here I just call

<h:commandButton value="Find" action="#{burstDataModel.search}" />

Methods in extended datamodel

 public void search () {
 update();

 datascrollerUI.getDatascroller().getDataTable().setFirst(0);
 }


 @Override
 public void update() {
 if (getSortFieldObject() != null) {
 String newSortField = getSortFieldObject().toString();
 if (newSortField.equals(sortField)) {
 descending = !descending;
 }
 sortField = newSortField;
 }
 detached = false;
 }

Based on the documentation I have read, after update(), detached is set to false and triggers wrappedKeys to be rebuilt from the dataprovider.

Have you used this successfully?
with EntityQuery ?

What scope do I put these in ?

Thanks for your response.
Franco

[daniel.soneira]

To be honest - I'm using "standard" jsf managed beans and don't have a clue about Seam.

In my case a simple replacement of a list (which is used for the table/datascroller) does the trick:

Similar to the code below

JSP

 <h:commandButton action="${controller.handleSearch}"/>
 <a4j:repeat id="resultTable" value="${model.resultList}" var="result">
 ...
 </a4j:repeat>

 <rich:datascroller for="resultTable"/>

Controller (request scope)

public void handleSearch {
 log().debug("handleSearch");
 model.setResultList(service.getEntitiesByFilter(model.getFilter()));
}

Model (session scope)

private Entity filter;
private List<Entity>resultList;

public List<Entity> getResultList() {
 return resultList;
}

public void setResultList(List<Entity> resultList) {
 this.resultList = resultList;
}

public Entity getFilter() {
 return filter;
}

public void setFilter(Entity filter) {
 this.filter = filter;
}