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## 6.2. < a4j:keepAlive >

### 6.2.1. Description

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

Table 6.3. a4j : keepAlive attributes

Attribute Name | Description
--- | ---
ajaxOnly | if true, bean value restored in ajax requests only.
beanName | name of bean for EL-expressions.

Table 6.4. Tag identification parameters

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

### 6.2.2. 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.

### 6.2.3. 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.

### 6.2.4. Relevant resources links

Here 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 here.

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