Retrieve pagination object from a Primefaces dataTable

Question

I am currently working with JSF 2 and Primefaces 5.2, more precisely with p:dataTable . I use p:dataTable with pagination.

From my Java bean, I can't find a way to retrieve any pagination component. I am particularly interested in an object where I can get the selected element in {RowsPerPageDropdown}

<p:dataTable
        var="item"
        value="#{items}"
        rows="10" 
        id="tableItems"      
        paginator="true" paginatorPosition="top" paginatorAlwaysVisible="true"
        paginatorTemplate="{CurrentPageReport} {PreviousPageLink} Page : {JumpToPageDropdown} {NextPageLink} NbrElements : {RowsPerPageDropdown}"
        rowsPerPageTemplate="#{fn:length(items)},10,20,50"
        currentPageReportTemplate="{startRecord}-{endRecord} / {totalRecords}" binding="#{tableComponent.table}">

By inspecting the page, the drop down menu id is tableItems_rppDD .

I tried finding it by printing component id out with a combination of FacesContext.getCurrentInstance().getViewRoot()...getChildren() and findComponent() but with no success.

Does anyone know how to get my hand on the paginator or if it is possible? Or is it a pure Javascript object?

Thanks a lot

Edit :

I am adding dynamically elements to my list ( p:dataTable + h:commandLink ) .

If you look the dataTable declaration, the first element of the {RowsPerPageDropdown} is the number of elements in the new list (let's call it n ). The first time around, if I select this first element from {RowsPerPageDropdown} , it displays n elements.

If I add a new element in the list, the first element of the {RowsPerPageDropdown} becomes n + 1 But the total number of elements displayed in the table is n (the newest element is in the next page).

I have fixed my problem by reimplementing with minor changes {CurrentPageReport}

Answer 1

Too long for a comment...

DataTable is a single UIComponent, and has not a paginator 'JSF component' (UIComponent).
So, every operation you need to do about pagination must be done directly on DataTable , or on DataModel (when passed as value attribute).

However, depending on what you need to do, you can access its attributes:

DataTable table = [find component somehow: UIComponent.getCurrentComponent(context), context.getViewRoot().findComponent(expr), ...]

// if you need to know currently selected RowsPerPageDropdown (page size)
int rows = table.getRows(); // table.getRowsToRender();

// or you can get the template
String rowsPerPageTemplate = table.getRowsPerPageTemplate();

// and split options
String[] options = rowsPerPageTemplate.split("[,\\s]+");

You can find how DataTable renders the html <select> dropdown in org.primefaces.component.paginator.RowsPerPageDropdownRenderer source code.

---

here you are a little example: 这里是一个小例子：

The example shows how to get the selected rows dropdown value on server side: choose a rows dropdown value and click the command button.

<p:growl id="messages" autoUpdate="true" showDetail="true"
    showSummary="true" />

<h:form>
    <p:dataTable id="table" var="elem" value="#{testTableBean.valueList}" rows="5"
        paginator="true"
        paginatorTemplate="{CurrentPageReport}  {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}"
        rowsPerPageTemplate="#{component.rowCount},5,10,15">
        <p:column>
            <h:outputText value="#{elem}" />
        </p:column>
    </p:dataTable>

    <p:commandButton action="#{testTableBean.execute}" process="@form" value="execute" />

    <p:commandButton process="@form" update="table"
            actionListener="#{testTableBean.valueList.add('value #' += testTableBean.valueList.size())}"
             value="add" />
</h:form>

and

@ManagedBean
@ViewScoped
public class TestTableBean implements Serializable
{
    private static final long serialVersionUID = 1L;

    private final List<String> valueList = new ArrayList<>();

    @PostConstruct
    public void init()
    {
        // add 25 dummy values
        for(int i = 0; i < 25; i++)
        {
            valueList.add("value #" + i);
        }
    }

    public void execute()
    {
        FacesContext context = FacesContext.getCurrentInstance();

        // get current component: CommandButton
        UIComponent component = UIComponent.getCurrentComponent(context);

        // get the naming container: HtmlForm
        UIComponent namingContainer = component.getNamingContainer();

        // find data table by id
        DataTable table = (DataTable) namingContainer.findComponent("table");

        // get the displayed rows value: this value is updated by DataTableRenderer.decode()
        // when user changes rows dropdown (previous ajax request)
        int rows = table.getRows();

        // add as message
        context.addMessage(null, new FacesMessage(FacesMessage.SEVERITY_INFO, "rows: " + rows, null));
    }

    public List<String> getValueList()
    {
        return valueList;
    }
}

: you don't need to rely on the html side because it is generated by renderers; ：您不需要依赖html端，因为它是由渲染器生成的； every information renderers know it is just available and accessible on server side.