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Since Tapestry 5.4.2, you can also easily invoke server-side event handlers using the @PublishEvents annotation and the t5/core/ajax JavaScript function, as explained in the "Invoking server-side event handler methods from JavaScript" section below.

Zones

Zones are Tapestry's approach to performing partial page updates. A Zone component renders as an HTML element, typically a <div>, and serves as a marker for where dynamically-updated content should be replaced. A zone is recognizable in the DOM because it will have the attribute data-container-type=zone. The client-side support for Zones is keyed off of this attribute and value.

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A Zone updated can be triggered by an EventLink, ActionLink or Select component, or by a Form. All of these components support the async and/or zone parameters. Clicking such a link will invoke an event handler method on the server as normal ... except that a partial page response is sent to the client, and the content of that response is used to update the Zone's <div> in place.

{float:right|background=#eee|padding=0 1em}
    *JumpStart Demo:*
    [AJAX ActionLink|

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https://tapestry-jumpstart.

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org/jumpstart/examples/ajax/actionlink]
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Event Handler Return Types

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@Inject
private Request request;

@InjectComponent
private Zone myZone;
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Object onActionFromSomeLink()
{
    // return either the zone body (ajax) or whole page (non-ajax)
    return request.isXHR() ? myZone.getBody() : null;
} 

Multiple Zone Updates

{float:right|background=#eee|padding=0 1em}
    *JumpStart Demo:*
    [AJAX Multiple Zone Update|

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https://tapestry-jumpstart.

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org/jumpstart/examples/ajax/multiplezoneupdate]
{float}

An event handler often needs to update multiple zones on the client side. To accomplish this, use an AjaxResponseRenderer, indicating the zones to update. You must know the client-side id for each zone to update (the best way for this is to lock down the zone's id using the id parameter of the Zone component).

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If a Zone is already visible, then a different effect function is used to highlight the change. By default, the highlight() function is called, which performs a yellow fade to highlight that the content of the Zone has changed. Alternatively, you can specify a different effect function with the Zone's update parameter:

To have Tapestry update a zone without the usual yellow highlight effect, just specify "show" for the update parameter:

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If you create a component that contains a zone, and you use that component in a loop, you'll likely need to set the client-side id like this:

<t:zone t:id="myzone" id="prop:componentResources.id">

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See this JumpStart Example for details.

The show and update function names (Tapestry 5.3 and earlier only) are converted to lower case; all the methods of Tapestry.ElementEffect should have all lower-case names. Because client-side JavaScript is so fluid (new methods may be added to existing objects), Tapestry makes no attempt to validate the function names ... however, if the names are not valid, then the default show and highlight methods will be used.

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There are also a number of Ajax-related examples at the   Tapestry JumpStart site.

Autocomplete Mixin

{float:right|background=#eee|padding=0 1em}
    *JumpStart Demo:*
    [Autocomplete Mixin|

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https://tapestry-jumpstart.

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org/jumpstart/examples/ajax/autocompletemixin]
{float}

The Autocomplete mixin exists to allow a text field to query the server for completions for a partially entered phrase. It is often used in situations where the field exists to select a single value from a large set, too large to successfully download to the client as a drop down list; for example, when the number of values to select from is numbered in the thousands.

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You can return an object array, a list, even a single object. You may return objects instead of strings ... and toString() will be used to convert them into client-side strings.

Invoking server-side event handler methods from JavaScript

Tapestry 5.4.2 introduced an API which makes it easy for server-side events to be invoked from JavaScript. On the server-side, you first need to annotate the event handler methods you want to expose with the @PublishEvent annotation. Then, in JavaScript, all you need to do is to call the existing existing t5/core/ajax function function, but with slightly different parameters.

The t5/core/ajax function has two parameters: url and options. Prior to Tapestry 5.4.2, the first one was difficult to get when doing AJAX requests to event handler methods. You needed to inject ComponentResources in your component class, call componentResources.createEventLink() for each event handler method, then pass all this information back to the browser through one of the JavaScriptSupport methods. For Tapestry 5.4.2 and later, your JavaScript code only needs to know the event name (also called event type) and optionally indicate a DOM element to be used as a starting point for finding the event URL.

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1. The element itself
2. The element's previous siblings, closest first (bottom-up)
3. The element's parents
4. The page's <body> <body> element

Here's one example:

public class PublishEventDemoComponent
{
    @OnEvent("answer")
    @PublishEvent
    JSONObject answer() {
        return new JSONObject("origin", "componentAnswer");
    }
    
    @PublishEvent
    JSONObject onAction()
    {
        return new JSONObject("origin", "componentAction");
    }   
}

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The template also has nothing special. When rendered, the component's events information is placed in the outer <div> ( <div id="component")>. 

We want to update the text of <p id="result"> with the value of the origin property of the returned JSON object when that element itself is clicked, so here's our JavaScript code, supposing we want to trigger the answer event:

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