[richfaces-issues] [JBoss JIRA] Commented: (RF-7849) datascroller does not calculate its page count correctly when used with dataTable & with SerializableDataModel...

[Nick Belaevski (JIRA)]

    [ https://jira.jboss.org/jira/browse/RF-7849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12485277#action_12485277 ] 

Nick Belaevski commented on RF-7849:
------------------------------------

1. Working demo involving serializable data model + rich:datscroller: http://livedemo.exadel.com/richfaces-demo/richfaces/dataTable.jsf?tab=dataModel&cid=4830393
ModifiableDataModel uses in-memory sorting, that's why range is indefinite in this case - it's unknown how many rows it would need to fetch from data source in order to fill the data window for the particular filtering conditions. Check this: http://livedemo.exadel.com/richfaces-demo/richfaces/dataTable.jsf?tab=modifiableDataModel&cid=4830656 for model that does sorting and filtering just in DB

2. Yes, rich:datascroller relies on the #getRowCount() method to know how many rows are there - your model should return correct result. Please take a look at UIData#getRowCount():

    /**
     * <p>Return the number of rows in the underlying data model.  If the number
     * of available rows is unknown, return -1.</p>
     *
     * @throws FacesException if an error occurs getting the row count
     */
    public int getRowCount() {

        return (getDataModel().getRowCount());

    }


> datascroller does not calculate its page count correctly when used with dataTable & with SerializableDataModel...
> -----------------------------------------------------------------------------------------------------------------
>
>                 Key: RF-7849
>                 URL: https://jira.jboss.org/jira/browse/RF-7849
>             Project: RichFaces
>          Issue Type: Bug
>          Components: component-tables
>    Affects Versions: 3.3.1
>         Environment: Windows XP; Richfaces 3.3.1.GA; MyFaces 1.2.6, facelets 1.1.14.  Project base generated with appfuse v2
>            Reporter: Jérôme JADOULLE
>
> ... or so it seems.
> As others, I am faced with the need to implement a server-side pagination so that only a subset of my data gets fetched from my backend (a Hibernate 3 "managed" database).
> I have read the examples explaining how to do this (see the links below) and tried to make them run but I encounter 2 main errors when testing:
> first, when implementing the walk method in the SerializableDataModel, the range parameter always returns 0 as its first row and -1 as the quantity.  
> When investigating in the source code, I found out that my walk method is in fact called by the  "modify" method of the "ModifiableModel" class. 
> Fact is that, the "range" parameter passed to the walk method is always created like this: "new SequenceRange(0, -1)", already meaning that, whatever happens, the values used in the range will be 0 and -1.
> Second point appears when I force the quantity of rows to a predefined value other than -1 (to see if the rest of the system works fine).  When doing this, the 20 first columns correctly get displayed in my table but, even if the getRowCount() method is correctly implemented as well (returning the total quantity of rows in my db), the datascroller uses the UIData.getRowCount() method to calculate the quantity of rows it totally contains (in order to know how to display itself) and this only returns the quantity of items actually present in an ArrayList used to store the rows to display.  
> Meaning that, whatever the quantity of rows present in my system, datascroller always thinks that the size is 20 (in this case).
> Don't know if I am clear enough.  If not, i'll post more information.
> Links followed to understand how to implement the datamodel:
> http://gochev.blogspot.com/2009/08/richfaces-server-side-paging-with.html
> http://eclecticprogrammer.com/2008/06/25/sorting-and-paginating-in-the-database-with-richfaces/

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