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:

Preventing a request

The third parameter of "notifyTopics", request, has a "cancel" property that can be used to prevent a request.

Example:

dojo.event.topic.subscribe("/request", function(data, type, request) {
  //cancel request
  request.cancel= true;
});

<s:url id="ajaxTest" value="/AjaxTest.action" />
 
<s:submit type="submit" theme="ajax" value="submit" notifyTopics="/request" href="%{ajaxTest}"/>

Indicators

Use indicators to notify the user that a request is in progress. The indicator should be hidden when the page is loaded.

This indicator is an image:

<img style="display:none" src="${pageContext.request.contextPath}/images/indicator.gif" alt="Loading..."/>

Topics

Topics provide an easy way to listen to and publish events.

To listen to a topic:

dojo.event.topic.subscribe("/refresh", function(param1, param2) {
  //this function will be called everytime "/refresh" is published
});

To publish a topic:

dojo.event.topic.publish("/refresh", "foo", "bar"); 

URL

The "href" attribute must contain a url built with the url tag.

Example:

<s:url id="ajaxTest" value="/AjaxTest.action" />
<s:div theme="ajax" href="%{ajaxTest}">
  Initial Content
</s:div>

Returning pages with AJAX Tags

Ajax tags can be used inside content returned from an asynchronous request, just like in regular pages.

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 topics. To define the topics that will trigger the refresh of the panel, use the "listenTopics" attribute. This tag will load its content when the page is loaded, unless "autoStart" is set to "false".

This div will refresh every time the topics "/refresh0" or "/refresh1" are published:

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:div theme="ajax" href="%{ajaxTest}" listenTopics="/refresh0,/refresh1"/>

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

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

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:div theme="ajax" href="%{ajaxTest}" updateFreq="2000" delay="3000"/>

The "autoStart" attribute 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 the topics "startTimerListenTopics" and "stopTimerListenTopics".

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

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:div theme="ajax" href="%{ajaxTest}" startTimerListenTopics="/startTimer" stopTimerListenTopics="/stopTimer" updateFreq="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. If you don't want to display the erro, set "showErrorTransportText" to "false".

This div uses custom error/loading messages:

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:div href="%{ajaxTest}" theme="ajax" errorText="There was an error" loadingText="reloading" updateFreq="5000"/>

If the loaded content 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 in 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's DOM node 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:url id="ajaxTest" value="/AjaxTest.action" />

<s:div href="%{ajaxTest}" 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:url id="ajaxTest" value="/AjaxTest.action" />

<s:div theme="ajax" href="%{ajaxTest}" handler="handler"/>

"notifyTopics" scenarios:

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. The "targets" attribute is optional.

Regular submit button that will update the content of div1:

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

<s:url id="ajaxTest" value="/AjaxTest.action" />
 
<s:submit type="submit" theme="ajax" value="submit" targets="div1" href="%{ajaxTest}"/>

Submit button using an image:

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

<s:url id="ajaxTest" value="/AjaxTest.action" />

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

If the submit button is used inside a form (href is not required on this case), 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", "formFilter" and "href". Note that in this case "href" is required.

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

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:submit type="submit" theme="ajax" href="%{ajaxTest}" formId="form1"/>	

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

"notifyTopics" scenarios:

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. The "targets" attribute is optional.

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:url id="ajaxTest" value="/AjaxTest.action" />

<s:a theme="ajax" href="%{ajaxTest}" targets="dev1,dev2">Update divs</s:a>

If the anchor tag is used inside a form (href is not required on this case), the form will be submitted asynchronously:

<s:form id="form" action="AjaxTest">
  <input type="textbox" name="data">
  <s:a theme="ajax">Submit form</s:a>		
</s:form>

Using the anchor tag to submit a form:

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

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:a theme="ajax" href="%{ajaxTest}" formId="form1">Submit form</s:a>

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

"notifyTopics" scenarios:

Tabbed Panel

The tabbedPanel tag can host static and dynamic(asynchronously loaded) tabs. Every div tag inside the tabbedPanel will be rendered as a tab. The "label" attribute is required for each tab, and will be used as caption. For more details on the dynamic tabs, see the "div" tag section. The tabbedPanel tag is in the "simple" theme bacause it does not contains any ajax functionality itself.

This tabbedPanel has one static, and one dynamic tab:

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:tabbedPanel>
    <s:div label="static">
        This is an static content tab.
    </s:div>
    <s:div href="%{ajaxTest}" theme="ajax" label="dynamic">
        This is a dynamic content tab. 
        The content of this div will be replaced with the text returned from "/AjaxTest.action"
    </s:div>
</s:tabbedPanel>  

Use the "labelposition" attribute to specify the side where the tab labels must be placed, possible values are "top" (default), "right", "bottom" and "left". Tabs can have a "close button" which will remove the tab from its tabbedPanel parent. The "close button" is hidden by default, to make it visible set the "closeButton" attribute to either "panel" (it will be placed on the tabbedPanel), or "tab" (it will be placed on each tab). By default the first tab will be selected, using the "selectedTab" attribute, you can specify the id of the tab to be selected when the page loads.

This tabbedPanel will place the tab labels on the left, with a "close" button on each tab, and will select the "dynamic" tab by default:

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:tabbedPanel labelposition="left" closeButton="tab" selectedTab="dynamic">
    <s:div label="static" id="static">
        This is an static content tab.
    </s:div>
    <s:div href="%{ajaxTest}" theme="ajax" label="dynamic" id="dynamic">
        This is a dynamic content tab. 
        The content of this div will be replaced with the text returned from "/AjaxTest.action"
    </s:div>
</s:tabbedPanel>  

TabbedPanel's height will be by default the same as the currently selected tab, use the "doLayout" attribute to force a fixed height.

This tabbedPanel's height is 300 px:

<s:url id="ajaxTest" value="/AjaxTest.action" />

<s:tabbedPanel id="test2" theme="simple" cssStyle="height: 300px;" doLayout="true">
  <s:div id="left" label="left">
      This is the left pane<br/>
      <s:form >
          <s:textfield name="tt" label="Test Text" /> 
          <br/>
          <s:textfield name="tt2" label="Test Text2" />
      </s:form>
  </s:div>
  <s:div theme="ajax"  href="%{ajaxTest}" id="ryh1" label="remote one" />
</s:tabbedPanel>

Autocompleter

The autocompleter tag loads its options asynchronously when the page loads, and suggests options based on the text entered in the textbox. If the attribute "autoComplete" is set to "true" (defaults to false), the autocompleter will make suggestions in the textbox, as the user types. The autocompleter will always display a dropdown with the options that have at least a partial match with the text entered in the textbox. If the user clicks on the dropdown button, all the options will be shown in the dropdown. To force the value to be a valid option set the attribute "forceValidOption" to "true" ("false" by default).

This is a simple autocompleter without textbox autocomplete:

<s:url id="json" value="/JSONList.action" />

<s:autocompleter theme="ajax" href="%{json}" autoComplete="false"/>

This tag can be used in the "simple" theme, without ajax functionality. When using this tag in the "simple" theme, the option to be selected by default can be specified using the "value" attribute. Use the "list" attribute to specify the available options:

<s:autocompleter theme="simple" list="{'apple','banana','grape','pear'}" value="grape"/>

By default the dropdown's height is 120 px, if the list contains just a few items and is smaller than 120 px, the dropdown's height will be adjusted to the size of the list. To change the default value for the dropdown's height use the "dropdownHeight" attribute.

This autocompleter dropdown's height is 180 px:

<s:url id="json" value="/JSONList.action" />

<s:autocompleter theme="ajax" href="%{json}" dropdownHeight="180"/>

When the topic specified in the "refreshListenTopic" attribute is published, the options in the autocompleter will be reloaded. If the "onValueChangedPublishTopic" attribute is given a value, every time the selected value changes, a topic with that name will be published. This two attributes can be use to link two autocompleters. The "formId" and "formFilter" attributes (see Div tag for examples) can be used to submit a form, when the request is made.

When the selected value in "Autocompleter 1" changes, the "/Refresh" is published, forcing "Autocompleter 2", to reloads its options, submitting the form "selectForm":

<s:url id="json" value="/JSONList.action" />

<form id="selectForm">
  Autocompleter 1 <s:autocompleter theme="simple" name="select" list="{'fruits','colors'}"  notifyTopics="/Refresh" />
</form>
  Autocompleter 2 <s:autocompleter theme="ajax" href="%{json}" formId="selectForm" listenTopics="/Refresh"/>

By default the autocompleter tag loads its options once, and makes suggestions based on those options. This is not the best approach if the action returns many options. The autocompleter tag can reload its options every time the user types in the textbox, setting "loadOnTextChange" to "true" ("false" by default). If "loadOnTextChange" is set to "true" the available options will be reloaded after the user types 3 characters (default), to specify the minimum number of characters, use "loadMinimumCount". On this case, it is probably desired to hide the dropdown arrow, setting "showDownArrow" to "false".

This autocompleter reloads its content everytime the user types into the textbox, and the text lenght is greater than or equal to 4:

<s:url id="json" value="/JSONList.action" />

<s:autocompleter theme="ajax" href="%{jsonList}" loadOnTextChange="true" loadMinimumCount="4" showDownArrow="false"/>

"notifyTopics" scenarios: