/*
 * Copyright 2002-2012 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
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.support;

import java.util.Collection;
import java.util.Map;

import org.springframework.lang.Nullable;
import org.springframework.ui.Model;
import org.springframework.web.servlet.FlashMap;

A specialization of the Model interface that controllers can use to select attributes for a redirect scenario. Since the intent of adding redirect attributes is very explicit -- i.e. to be used for a redirect URL, attribute values may be formatted as Strings and stored that way to make them eligible to be appended to the query string or expanded as URI variables in org.springframework.web.servlet.view.RedirectView. 
This interface also provides a way to add flash attributes. For a general overview of flash attributes see FlashMap. You can use RedirectAttributes to store flash attributes and they will be automatically propagated to the "output" FlashMap of the current request. 
Example usage in an @Controller: 
@RequestMapping(value = "/accounts", method = RequestMethod.POST)
public String handle(Account account, BindingResult result, RedirectAttributes redirectAttrs) {
  if (result.hasErrors()) {
    return "accounts/new";
  }
  // Save account ...
  redirectAttrs.addAttribute("id", account.getId()).addFlashAttribute("message", "Account created!");
  return "redirect:/accounts/{id}";
}

A RedirectAttributes model is empty when the method is called and is never
used unless the method returns a redirect view name or a RedirectView.
After the redirect, flash attributes are automatically added to the model
of the controller that serves the target URL.
Author:
Rossen Stoyanchev
Since:
3.1/**
 * A specialization of the {@link Model} interface that controllers can use to
 * select attributes for a redirect scenario. Since the intent of adding
 * redirect attributes is very explicit --  i.e. to be used for a redirect URL,
 * attribute values may be formatted as Strings and stored that way to make
 * them eligible to be appended to the query string or expanded as URI
 * variables in {@code org.springframework.web.servlet.view.RedirectView}.
 *
 * <p>This interface also provides a way to add flash attributes. For a
 * general overview of flash attributes see {@link FlashMap}. You can use
 * {@link RedirectAttributes} to store flash attributes and they will be
 * automatically propagated to the "output" FlashMap of the current request.
 *
 * <p>Example usage in an {@code @Controller}:
 * <pre class="code">
 * &#064;RequestMapping(value = "/accounts", method = RequestMethod.POST)
 * public String handle(Account account, BindingResult result, RedirectAttributes redirectAttrs) {
 *   if (result.hasErrors()) {
 *     return "accounts/new";
 *   }
 *   // Save account ...
 *   redirectAttrs.addAttribute("id", account.getId()).addFlashAttribute("message", "Account created!");
 *   return "redirect:/accounts/{id}";
 * }
 * </pre>
 *
 * <p>A RedirectAttributes model is empty when the method is called and is never
 * used unless the method returns a redirect view name or a RedirectView.
 *
 * <p>After the redirect, flash attributes are automatically added to the model
 * of the controller that serves the target URL.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public interface RedirectAttributes extends Model {

	@Override
	RedirectAttributes addAttribute(String attributeName, @Nullable Object attributeValue);

	@Override
	RedirectAttributes addAttribute(Object attributeValue);

	@Override
	RedirectAttributes addAllAttributes(Collection<?> attributeValues);

	@Override
	RedirectAttributes mergeAttributes(Map<String, ?> attributes);

	
Add the given flash attribute.
Params:
attributeName – the attribute name; never null
attributeValue – the attribute value; may be null/**
	 * Add the given flash attribute.
	 * @param attributeName the attribute name; never {@code null}
	 * @param attributeValue the attribute value; may be {@code null}
	 */
	RedirectAttributes addFlashAttribute(String attributeName, @Nullable Object attributeValue);

	
Add the given flash storage using a generated name. 
Params:
attributeValue – the flash attribute value; never null/**
	 * Add the given flash storage using a
	 * {@link org.springframework.core.Conventions#getVariableName generated name}.
	 * @param attributeValue the flash attribute value; never {@code null}
	 */
	RedirectAttributes addFlashAttribute(Object attributeValue);

	
Return the attributes candidate for flash storage or an empty Map.
/**
	 * Return the attributes candidate for flash storage or an empty Map.
	 */
	Map<String, ?> getFlashAttributes();
}