The <a4j:keepAlive> tag allows to keep a state of a bean between requests.

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 Exceptions 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.

Table of <a4j:keepAlive> attributes.

Visit KeepAlive page at RichFaces Livedemo for examples of component usage and their sources.

Search the RichFaces Users forum for some additional information about usage of component.