/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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package org.springframework.web.bind.support;

import org.springframework.lang.Nullable;
import org.springframework.web.context.request.WebRequest;

Strategy interface for storing model attributes in a backend session.
Author:
Juergen Hoeller
See Also:
SessionAttributes
Since:
2.5/**
 * Strategy interface for storing model attributes in a backend session.
 *
 * @author Juergen Hoeller
 * @since 2.5
 * @see org.springframework.web.bind.annotation.SessionAttributes
 */
public interface SessionAttributeStore {

	
Store the supplied attribute in the backend session.
Can be called for new attributes as well as for existing attributes.
In the latter case, this signals that the attribute value may have been modified.
Params:
request – the current request
attributeName – the name of the attribute
attributeValue – the attribute value to store/**
	 * Store the supplied attribute in the backend session.
	 * <p>Can be called for new attributes as well as for existing attributes.
	 * In the latter case, this signals that the attribute value may have been modified.
	 * @param request the current request
	 * @param attributeName the name of the attribute
	 * @param attributeValue the attribute value to store
	 */
	void storeAttribute(WebRequest request, String attributeName, Object attributeValue);

	
Retrieve the specified attribute from the backend session.
This will typically be called with the expectation that the attribute is already present, with an exception to be thrown if this method returns null. 
Params:
request – the current request
attributeName – the name of the attribute
Returns:
the current attribute value, or null if none/**
	 * Retrieve the specified attribute from the backend session.
	 * <p>This will typically be called with the expectation that the
	 * attribute is already present, with an exception to be thrown
	 * if this method returns {@code null}.
	 * @param request the current request
	 * @param attributeName the name of the attribute
	 * @return the current attribute value, or {@code null} if none
	 */
	@Nullable
	Object retrieveAttribute(WebRequest request, String attributeName);

	
Clean up the specified attribute in the backend session.
Indicates that the attribute name will not be used anymore.
Params:
request – the current request
attributeName – the name of the attribute/**
	 * Clean up the specified attribute in the backend session.
	 * <p>Indicates that the attribute name will not be used anymore.
	 * @param request the current request
	 * @param attributeName the name of the attribute
	 */
	void cleanupAttribute(WebRequest request, String attributeName);

}