# a4j

## Tag poll

- Description:

    The <a4j:poll> component allows periodical sending of Ajax requests to the server. It is used for repeatedly updating a page at specific time intervals.

    @author shura

- Component Information
  Info | Value
  --- | ---
  Component Type | `org.richfaces.Poll`
  Handler Class | `org.richfaces.view.facelets.html.AjaxPollHandler`
  Renderer Type | `org.richfaces.PollRenderer`
  Description | The <a4j:poll> component allows periodical sending of Ajax requests to the server. It is used for repeatedly updating a page at specific time intervals. @author shura

- Attributes
  Name | Required | Type | Description
  --- | --- | --- | ---
  `action` | `false` | `javax.el.ValueExpression` (must evaluate to `javax.faces.el.MethodBinding`) | MethodExpression representing the application action to invoke when this component is activated by the user. The expression must evaluate to a public method that takes no parameters, and returns an Object (the toString() of which is called to derive the logical outcome) which is passed to the NavigationHandler for this application.
  `actionListener` | `false` | `javax.el.ValueExpression` (must evaluate to `javax.faces.el.MethodBinding`) | MethodExpression representing an action listener method that will be notified when this component is activated by the user. The expression must evaluate to a public method that takes an ActionEvent parameter, with a return type of void, or to a public method that takes no arguments with a return type of void. In the latter case, the method has no way of easily knowing where the event came from, but this can be useful in cases where a notification is needed that "some action happened".
  `binding` | `false` | `javax.el.ValueExpression` (must evaluate to `javax.faces.component.UIComponent`) | The value binding expression used to wire up this component to a component property of a JavaBean class
  `bypassUpdates` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | If "true", after process validations phase it skips updates of model beans on a force render response. It can be used for validating components input.
  `data` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.Object`) | Serialized (on default with JSON) data passed to the client by a developer on an AJAX request. It's accessible via "event.data" syntax. Both primitive types and complex types such as arrays and collections can be serialized and used with data
  `enabled` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | Enables/disables polling to the server. Using Expression Language (EL), the enabled attribute can point to a bean property to apply a particular attribute value
  `execute` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.Object`) | Ids of components that will participate in the "execute" portion of the Request Processing Lifecycle. Can be a single id, a space or comma separated list of Id's, or an EL Expression evaluating to an array or Collection. Any of the keywords "@this", "@form", "@all", "@none", "@region" may be specified in the identifier list. Some components make use of additional keywords
  `id` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The component identifier for this component. This value must be unique within the closest parent component that is a naming container.
  `immediate` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | Flag indicating that, if this component is activated by the user, notifications should be delivered to interested listeners and actions immediately (that is, during Apply Request Values phase) rather than waiting until Invoke Application phase.
  `interval` | `false` | `javax.el.ValueExpression` (must evaluate to `int`) | Specifies the time in milliseconds between requests. The default for this value is 1000 ms (1 second)
  `limitRender` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | If "true", render only those ids specified in the "render" attribute, forgoing the render of the auto-rendered panels
  `onbeforedomupdate` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called after the ajax response comes back, but before the DOM is updated
  `onbegin` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called before an ajax request.
  `oncomplete` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called after the DOM is updated
  `ontimer` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called after the timer counts down, but before the Ajax request is initiated
  `render` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.Object`) | Ids of components that will participate in the "render" portion of the Request Processing Lifecycle. Can be a single id, a space or comma separated list of Id's, or an EL Expression evaluating to an array or Collection. Any of the keywords "@this", "@form", "@all", "@none", "@region" may be specified in the identifier list. Some components make use of additional keywords
  `rendered` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | Flag indicating whether or not this component should be rendered (during Render Response Phase), or processed on any subsequent form submit. The default value for this property is true.
  `resetValues` | `false` | `javax.el.ValueExpression` (must evaluate to `boolean`) | If true, indicate that this particular Ajax transaction is a value reset transaction. This will cause resetValue() to be called on any EditableValueHolder instances encountered as a result of this ajax transaction. If not specified, or the value is false, no such indication is made.
  `status` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | Name of the request status component that will indicate the status of the Ajax request
  `value` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.Object`) | The current value of this component.

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