org.apache.tapestry5.corelib.components.EventLink

A close relative of org.apache.tapestry5.corelib.components.ActionLink except in two ways. First, the event that it triggers is explicitly controlled, rather than always "action". Second, the event is triggered in its container. This allows slightly shorter URLs but also allows multiple components within the same container to generate identical URLs for common actions.

[JavaDoc]

Component Inheritance

Component Parameters

NameTypeFlagsDefaultDefault PrefixDescription
anchorStringNOT Allow NullliteralAn anchor value to append to the generated URL (the hash separator will be added automatically).
contextObjectNOT Allow NullpropThe context for the link (optional parameter). This list of values will be converted into strings and included in the URI. The strings will be coerced back to whatever their values are and made available to event handler methods.
disabledbooleanNOT Allow NullfalsepropIf true, then then no link element is rendered (and no informal parameters as well). The body is, however, still rendered.
eventStringNOT Allow NullliteralThe name of the event to be triggered in the parent component. Defaults to the id of the component. An org.apache.tapestry5.corelib.components.ActionLink triggers an "action" event on itself, and EventLink component triggers any arbitrary event on its container.
zoneStringNOT Allow NullliteralBinding the zone parameter turns the link into a an Ajax control that causes the related zone to be updated.

Examples

This example is from Tapestry itself, from the GridColumns component that displays the columns titles across to the top of a Grid. We've simplified the example somewhat to focus in on the use of the EventLink component.

GridColumns.tml

<thead xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd">
    <tr>
        <th t:type="Loop" source="columnNames" value="columnName">
            <a t:id="sort">${columnModel.label}</a>
            <a t:id="sort2">
                <img src="${icon}" id="${columnModel.id}:sort" class="t-sort-icon" alt="${iconLabel}"/>
            </a>
        </th>
    </tr>
</thead>

GridColumns.java (partial)

public class GridColumns
{
    . . .

    @Component(parameters = {"event=sort", "context=columnModel.id"})
    private EventLink _sort, _sort2;

    void onSort(String columnId)
    {
        if (columnId.equals(_sortColumnId))
        {
            _sortAscending = !_sortAscending;
        }
        else
        {
            _sortColumnId = columnId;
            _sortAscending = true;
        }
    }

}
The advantage of the EventLink component is that instead of having two identical event handler methods, onActionFromSort() and onActionFromSort2(), we have a single event handler method, onSort(), that covers events triggered by either component. In addition, the URLs for the two components will be identical, whereas if using ActionLink components, the URLs would be slightly different, to reflect to two different component ids. This example also shows the advantages of defining the component in the Java class, using the @Component annotation, rather than in the template (as we do in most examples). We can simply define two fields with the same configuration.

Notes

The event parameter is often omitted; it defaults to the component's id ... you will often specify the component id, or a specific event name, but not both.

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