a4j:keepAlive

Tag identification parameters

Name | Value
--- | ---
component-type | org.ajax4jsf.components.KeepAlive
component-family | org.ajax4jsf.components.AjaxKeepAlive
component-class | org.ajax4jsf.components.AjaxKeepAlive

## Using the tag on a Page

To create the simplest variant on a page use the following syntax:

Example:

    <a4j:keepAlive beanName = "testBean"/>

Note, that to be put into the request scope the pointed bean should be registered inside faces-config.xml file and marked with org.ajax4jsf.model.KeepAlive annotation.

A bean instance in the request scope could also be saved directly through the declaration of `@KeepAlive` annotation inside the bean.

## Key attributes and ways of usage

If a managed bean is declared with request scope in the configuration file with the help of <managed-bean-scope> tag then the life-time of this bean instance is valid only for the current request. Any attempts to make a reference to the bean instance after the request end will throw in Illegal Argument Exception by the server. To avoid these kinds of Exception, component <a4j:keepAlive> is used to maintain the state of the whole bean object among subsequent request.

Example:

    <a4j:keepAlive beanName = "#{myClass.testBean}"/>

The "beanName" attribute defines the request scope bean name you'd like to re-use. Note that this attribute must point to a legal JSF EL expression which resolves to a managed mean instance. For example for the above code the class definition may look like this one:

    class MyClass{
    	...
    	private TestBean testBean;
    	// Getters and Setters for testBean.
    	...
    }

The "ajaxOnly" attribute declares whether the value of the bean should be available during a non-Ajax request. If the value of this attribute is "true" a request scope bean keeps the same value during Ajax requests from the given page. If a non-Ajax request is sent from this page the bean is re-created as a regular request scope bean.

## Relevant resources links

On the component LiveDemo page you can see the example of <a4j:keepAlive> usage and sources for the given example.

Some additional information about usage of component can be found on theAjax4JSF Users Forum.