org.apache.tapestry5.corelib.components
Class EventLink

java.lang.Object
  org.apache.tapestry5.corelib.base.AbstractLink
      org.apache.tapestry5.corelib.base.AbstractComponentEventLink
          org.apache.tapestry5.corelib.components.EventLink

All Implemented Interfaces:

ClientElement

public class EventLink
extends AbstractComponentEventLink

A close relative of 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.

Component Parameters

Name	Description	Type	Flags	Default	Default Prefix	Since
anchor	An anchor value to append to the generated URL (the hash separator will be added automatically).	String			literal
context	The 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.	Object			prop
disabled	If true, then then no link element is rendered (and no informal parameters as well). The body is, however, still rendered.	boolean		false	prop
event	The 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.	String			literal
parameters	If specified, the parameters are added to the link as query parameters in key=value fashion. Values will be coerced to string using value encoder; keys should be Strings.	java.util.Map	Not Null		prop	5.3
zone	Binding the zone parameter turns the link into a an Ajax control that causes the related zone to be updated.	String			literal

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.

Constructor Summary

EventLink()

Method Summary

protected Link

createLink(Object[] eventContext) Invoked to create the Link that will become the href attribute of the output.

Methods inherited from class org.apache.tapestry5.corelib.base.AbstractLink

addParameters, getClientId, getLink, isDisabled, writeLink

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EventLink

public EventLink()

Method Detail

createLink

protected Link createLink(Object[] eventContext)

Description copied from class: AbstractComponentEventLink

Invoked to create the Link that will become the href attribute of the output.

Specified by:

createLink in class AbstractComponentEventLink

Parameters:

eventContext - the context as an object array, possibly null