Ajax Tags

Struts 2 provides a set of tags to help you ajaxify your applications, most of them inherited from Webwork, and based on Dojo. Dojo 0.4 is included in Struts 2.

Common Attributes

These attributes are common to all the ajax tags:

Div

The div tag is a content area that can load its content asynchronously. The div tag can be forced to reload its content using a topic. To defined the topic that will trigger the refresh of the panel, use the "refreshListenTopic" attribute.

This div will refresh every time the topic "/refresh" is published:

<s:div theme="ajax" href="/AjaxTest.action" refreshListenTopic="/refresh"/>

To publish this topic use this in your Javascript code:

dojo.event.topic.publish("/refresh");

The div tag can be configured to update its content periodically, using a timer. Use the "updateInterval" attribute to set the interval for the mentioned timer; this value is expressed in milliseconds. If "autoStart" is set to true, "delay" can be used to force the timer to wait for the "delay"(in milliseconds also) period before starting.

This div will refresh periodically every 2 seconds, starting 3 seconds after the page is loaded:

<s:div theme="ajax" href="/AjaxTest.action" updateInterval="2000" delay="3000"/>

There is an "autoStart" attribute that controls whether the timer will be started when the page is loaded, its value is "true" by default. The timer can be started and stopped using topics using "startTimerListenTopic" and "stopTimerListenTopic".

This div will not start the timer by default and will listen to the start/stop topics to control the timer:

<s:div theme="ajax" href="/AjaxTest.action" startTimerListenTopic="/startTimer" stopTimerListenTopic="/stopTimer" updateInterval="3000" autoStart="false"/>

The div panel shows "Loading..." by default when the request is in process. To customize this text, use the "loadingText" attribute. If an error of any sort occurs, the error will be shown in the div area, to customize the error message, use the "errorText" attribute.

This div uses custom error/loading messages:

<s:div href="/AjaxTest.action" theme="ajax" errorText="There was an error" loadingText="reloading" updateInterval="5000"/>

If the loaded text contains Javascript code sections, these sections will be executed if the "executeScripts" attribute is set to true.

If parameters need to be passed to the url, the "formId" attribute can be used to specify a form whose fields will be serialized and passed on the request as parameters. The attribute "formFilter" can bet set to the name of a Javascript function that will be used to filter the fields of "formId". The "formFilter" function will be called for each field, passing the field as a parameter, and must return true if the field is to be included, or false otherwise.

This div will submit the field "firstName", of the form "userData" and ignore other fields:

<script type="text/javascript">
  function filter(field) {
    return field.name == "firstName";
  }
</script>

<form id="userData">
  <label for="firstName">First Name</label>
  <input type="textbox" id="firstName" name="firstName">
  <label for="lastName">Last Name</label>
  <input type="textbox" id="lastName" name="lastName">
</form>
<s:div href="/AjaxTest.action" theme="ajax" formId="userData" formFilter="filter"/>

If the attribute "handler" is set, the Javascript function specified by its value will be called, instead of making the request. Use the "handler" function when you want to handle the request yourself.

This div will not make any request, and will just call the function "handler". The first parameter of the function is the Dojo widget for the div, and the second the DOM node for the div.

<script type="text/javascript">
   function handler(widget, node) {
     alert('I will handle this myself!');
     node.innerHTML = "Done";
   }
</script>

<s:div theme="ajax" href="/AjaxTest.action" handler="handler"/>

Submit

The submit tag can be used to update the content of its "targets" attribute with text returned from the asynchronous request. "targets" is a comma-delimited list of element ids.

Regular submit button that will update the content of div1:

<div id="div1">Div 1</div>
 
<s:submit type="submit" theme="ajax" value="submit" targets="div1" href="/AjaxTest.action"/>

Submit button using an image:

<div id="div1">Div 1</div>

<s:submit type="image" theme="ajax" label="Alt Text" targets="div1" src="${pageContext.request.contextPath}/images/struts-rocks.gif" href="/AjaxTest.action"/>

If the submit button is used inside a form, the form will be submitted asynchronously:

<s:form id="form" action="AjaxTest">
  <input type="textbox" name="data">
  <s:submit type="button" theme="ajax" label="Update Content"/>		
</s:form>

A submit button can be used to submit a form, even if it is outside the form, using "formId" and "formFilter" and "href". Note that in this case "href" is required.

<s:form id="form1">
  <input type="textbox" name="data">	
</s:form>

<s:submit type="submit" theme="ajax" href="/AjaxTest.action" formId="form1"/>	

See the Div tag for examples on how to use "handler", "beforeLoading", "afterLoading", "loadingText" and "errorText"

Anchor

The anchor tag like the submit tag can be used to update the content of its "targets" attribute with text returned from the asynchronous request. "targets" is a comma-delimited list of element ids.

This anchor will update the content of div1 and div2 with text returned form "/AjaxTest.action"

<div id="div1">Div 1</div>
<div id="div2">Div 2</div>

<s:a theme="ajax" href="/AjaxTest.action" targets="dev1,dev2">Update divs</s:a>

See the Div tag for examples on how to use "handler", "beforeLoading", "afterLoading", "loadingText" and "errorText"