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package javax.servlet;

import java.util.EventListener;

Interface for receiving notification events about ServletRequest
attribute changes.
Notifications will be generated while the request
is within the scope of the web application. A ServletRequest
is defined as coming into scope of a web application when it
is about to enter the first servlet or filter of the web
application, and as going out of scope when it exits the last
servlet or the first filter in the chain.
In order to receive these notification events, the implementation class must be either declared in the deployment descriptor of the web application, annotated with WebListener, or registered via one of the addListener methods defined on ServletContext. 
The order in which implementations of this interface are invoked is
unspecified.
Since:
Servlet 2.4/**
 * Interface for receiving notification events about ServletRequest
 * attribute changes.
 *
 * <p>Notifications will be generated while the request
 * is within the scope of the web application. A ServletRequest
 * is defined as coming into scope of a web application when it
 * is about to enter the first servlet or filter of the web
 * application, and as going out of scope when it exits the last
 * servlet or the first filter in the chain.
 *
 * <p>In order to receive these notification events, the implementation
 * class must be either declared in the deployment descriptor of the web
 * application, annotated with {@link javax.servlet.annotation.WebListener},
 * or registered via one of the addListener methods defined on
 * {@link ServletContext}.
 *
 * <p>The order in which implementations of this interface are invoked is
 * unspecified.
 *
 * @since Servlet 2.4
 */

public interface ServletRequestAttributeListener extends EventListener {

    
Receives notification that an attribute has been added to the
ServletRequest.
Params:
srae – the ServletRequestAttributeEvent containing the 
ServletRequest and the name and value of the attribute that was
added
Implementation Requirements:

The default implementation takes no action./**
     * Receives notification that an attribute has been added to the
     * ServletRequest.
     *
     * @param srae the ServletRequestAttributeEvent containing the 
     * ServletRequest and the name and value of the attribute that was
     * added
     *
     * @implSpec
     * The default implementation takes no action.
     */
    default public void attributeAdded(ServletRequestAttributeEvent srae) {}

    
Receives notification that an attribute has been removed from the
ServletRequest.
Params:
srae – the ServletRequestAttributeEvent containing the 
ServletRequest and the name and value of the attribute that was
removed
Implementation Requirements:

The default implementation takes no action./**
     * Receives notification that an attribute has been removed from the
     * ServletRequest.
     *
     * @param srae the ServletRequestAttributeEvent containing the 
     * ServletRequest and the name and value of the attribute that was
     * removed
     *
     * @implSpec
     * The default implementation takes no action.
     */
    default public void attributeRemoved(ServletRequestAttributeEvent srae) {}

    
Receives notification that an attribute has been replaced on the
ServletRequest.
Params:
srae – the ServletRequestAttributeEvent containing the 
ServletRequest and the name and (old) value of the attribute
that was replaced
Implementation Requirements:

The default implementation takes no action./**
     * Receives notification that an attribute has been replaced on the
     * ServletRequest.
     *
     * @param srae the ServletRequestAttributeEvent containing the 
     * ServletRequest and the name and (old) value of the attribute
     * that was replaced
     *
     * @implSpec
     * The default implementation takes no action.
     */
    default public void attributeReplaced(ServletRequestAttributeEvent srae) {}
}