# a4j

## Tag push

- Description:

    The <a4j:push> component performs real-time updates on the client side from events triggered at the server side. The events are pushed out to the client through the RichFaces messaging queue (which is bound to Java Messaging Service - JMS). When the <a4j:push> component is triggered by a server event, it can in turn cause Ajax updates and changes.

    @author Nick Belaevski @author Lukas Fryc

- Component Information
  Info | Value
  --- | ---
  Component Type | `org.richfaces.Push`
  Display Name | None
  Handler Class | None
  Renderer Type | `org.richfaces.PushRenderer`
  Description | The <a4j:push> component performs real-time updates on the client side from events triggered at the server side. The events are pushed out to the client through the RichFaces messaging queue (which is bound to Java Messaging Service - JMS). When the <a4j:push> component is triggered by a server event, it can in turn cause Ajax updates and changes. @author Nick Belaevski @author Lukas Fryc

- Attributes
  Name | Required | Type | Description
  --- | --- | --- | ---
  `address` | `true` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | References the topic on the JMS server that contains the pushed messages
  `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
  `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.
  `ondataavailable` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called when a push notification is received
  `onerror` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called when an error has occurred with the push notifications
  `onsubscribed` | `false` | `javax.el.ValueExpression` (must evaluate to `java.lang.String`) | The client-side script method to be called when push is subscribed successfully to the topic.
  `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.

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