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 *
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
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package javax.servlet;

import java.util.EventListener;

/**
 * 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.
     *
     * @param srae the ServletRequestAttributeEvent containing the 
     * ServletRequest and the name and value of the attribute that was
     * added
     */
    public void attributeAdded(ServletRequestAttributeEvent srae);

    /**
     * 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
     */
    public void attributeRemoved(ServletRequestAttributeEvent srae);

    /**
     * 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
     */
    public void attributeReplaced(ServletRequestAttributeEvent srae);
}