org.springframework.web.servlet

## Interface FlashMapManager

- All Known Implementing Classes:
    AbstractFlashMapManager, SessionFlashMapManager

      public interface FlashMapManager

  A strategy interface for retrieving and saving FlashMap instances. See `FlashMap` for a general overview of flash attributes.
  Since:
    3.1
  Author:
    Rossen Stoyanchev
  See Also:
    `FlashMap`

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `FlashMap` | `retrieveAndUpdate(HttpServletRequest request, HttpServletResponse response)` Find a FlashMap saved by a previous request that matches to the current request, remove it from underlying storage, and also remove other expired FlashMap instances.
    `void` | `saveOutputFlashMap(FlashMap flashMap, HttpServletRequest request, HttpServletResponse response)` Save the given FlashMap, in some underlying storage and set the start of its expiration period.

- - ### Method Detail

    - #### retrieveAndUpdate

          FlashMap retrieveAndUpdate(HttpServletRequest request,
                                   HttpServletResponse response)

      Find a FlashMap saved by a previous request that matches to the current request, remove it from underlying storage, and also remove other expired FlashMap instances.

      This method is invoked in the beginning of every request in contrast to `saveOutputFlashMap(org.springframework.web.servlet.FlashMap, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)`, which is invoked only when there are flash attributes to be saved - i.e. before a redirect.

      Parameters:
        `request` - the current request
        `response` - the current response
      Returns:
        a FlashMap matching the current request or `null`

    - #### saveOutputFlashMap

          void saveOutputFlashMap(FlashMap flashMap,
                                HttpServletRequest request,
                                HttpServletResponse response)

      Save the given FlashMap, in some underlying storage and set the start of its expiration period.

      Note: Invoke this method prior to a redirect in order to allow saving the FlashMap in the HTTP session or in a response cookie before the response is committed.

      Parameters:
        `flashMap` - the FlashMap to save
        `request` - the current request
        `response` - the current response