RichFaces4: lazy loading with dataTable and dataScroller

[runk]

Hi,

I actually couldn't find any useful solutions to this topic. So what is the right way to implement lazy loading in rf4? Obviously I don't want to load all the data on each request. Can I override parts of the dataScroller and dataTable model so I can at least come close to lazy loading? For example if I want to load e-mails to a dataTable I don't want to load all of them but maybe 10 at a time. I also don't want to hold open sessions to the mail server across requests. It would be great if anyone could give me some hints.

10x

[ilya_shaikovsky]

one of the samples in developers demo already contains code which loads data partially using JPA based model http://anonsvn.jboss.org/repos/richfaces/branches/4.0.X/examples/iteration-demo/

soon it will be migrated to the richfaces-showcase

[runk]

Hi Ilya,

thanks for your answer. However this example looks to be for the tree stuff. I don't quite need that. I found some posts suggesting to implement org.richfaces.model.DataProvider and org.richfaces.model.ExtendedTableDataModel but I guess this is no longer relevant (RichFaces4).

I need lazy loading with rich:dataTable and rich:dataScroller.

10x

[ilya_shaikovsky]

no it's not for tree stuff

see:

http://anonsvn.jboss.org/repos/richfaces/branches/4.0.X/examples/iteration-demo/src/main/java/org/richfaces/demo/JPADataModel.java

[ilya_shaikovsky]

it's probably slightly more complex than you need because filtering/sorting also present there. but you should be able to get the idea of just ExtendedDataModel from there. Just ignore methods which belongs to Arrangeable interface.

[runk]

Alright, I'll try it out. Thanks a lot.

[runk]

Hi,

I managed to get it working. Here's a very very simple implementation of org.ajax4jsf.model.ExtendedDataModel:

import javax.faces.context.FacesContext;
import org.ajax4jsf.model.DataVisitor;
import org.ajax4jsf.model.ExtendedDataModel;
import org.ajax4jsf.model.Range;
import org.ajax4jsf.model.SequenceRange;

public class TestDataModel extends ExtendedDataModel<String> {
    private String[] data = new String[] {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"};
    private Integer rowKey = null;

    @Override
    public void setRowKey(Object o) {
        rowKey = (Integer) o;
    }

    @Override
    public Object getRowKey() {
        return rowKey;
    }

    @Override
    public void walk(FacesContext fc, DataVisitor dv, Range range, Object o) {
        SequenceRange sr = (SequenceRange) range;
        int currentRow = sr.getFirstRow();
        int rows = sr.getRows();
        for(int i = 0; i < rows; i++) {
            dv.process(fc, currentRow++, o);
        }
    }

    @Override
    public boolean isRowAvailable() {
        return rowKey != null;
    }

    @Override
    public int getRowCount() {
        return data.length;
    }

    @Override
    public String getRowData() {
        return data[rowKey];
    }

    @Override
    public int getRowIndex() {
        return -1;
    }

    @Override
    public void setRowIndex(int rowIndex) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Object getWrappedData() {
        throw new UnsupportedOperationException();
    }

    @Override
    public void setWrappedData(Object data) {
        throw new UnsupportedOperationException();
    }
}

and this is how it's used:

        <rich:dataTable value="#{test.model}" var="i" rows="2" >
            <rich:column>
                #{i}
            </rich:column>
            <f:facet name="footer">
                <rich:dataScroller />
            </f:facet>
        </rich:dataTable>

where #{test.model} is an instance of TestDataModel.

Basically your "lazy" code should go into the walk() method.

10x again Ilya

[nikh123123]

I'm using similar logic except that the data is lazily loaded from a webserivce and hence my getRowCount method returns totalResults instead of the current list size. And I call the webservice method in the walk method. I have a few commandLinks in my dataTable. and every time I click on the commandLink, the walk method is executed. which in turn calls the web service which I do not want to happen. What could be the cause of this?

[nikh123123]

I'm kinda stuck here. Can someone point me to the right direction please?

[runk]

Apparently the form which your data table is in gets posted when you click on the command links (which is normal). That's why the walk() method is called again ... your data table gets posted along your command links. You can try to nest an AJAX component and specify what exactly needs to be posted as part of your request.

[nikh123123]

Thanks for the reply Ric! Ok do you mean I need to use a component like a4j:commandLink with an execute=@this or @region?

[runk]

Yes, either a4j:commandLink or a4j:ajax.

Good luck.

[elisei]

Hi all,

I also found a nice method here:

http://stackoverflow.com/questions/1197055/lazy-data-loading-with-richdatatable-and-richdatatablescroller

I thought it would be easier just to implement the DataProvider. But, as I see, the ExtendedTableDataModel isn't part of Richfaces 4.0.0.Final any more, right?

/Elisei

[jonleyo]

Be careful if you're loading some data under the "walk" method.

It is invoked during "render response" phase.

If you're are trying to fetch with a database, you could have a surprise exception.