SQL Server

Fetch Web Pages from Local Cache

See more HTTP Examples

Demonstrates how to keep a local cache to avoid re-fetching web pages. SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- This example assumes the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @http int
    EXEC @hr = sp_OACreate 'Chilkat.Http', @http OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- Define a cache directory and set the number of levels based on the anticipated size of the cache.
    EXEC sp_OAMethod @http, 'AddCacheRoot', NULL, 'c:/example/httpCache/'

    -- up to 256 sub-directories under the cache root will be created as needed to hold cached GET's.
    EXEC sp_OASetProperty @http, 'NumCacheLevels', 1

    -- Tell the http object to fetch from the cache if possible.
    EXEC sp_OASetProperty @http, 'FetchFromCache', 1

    -- Also tell the http object to update the cache with newly fetched pages.
    EXEC sp_OASetProperty @http, 'UpdateCache', 1

    -- This HTTP GET should result in a cache file getting created.
    DECLARE @html nvarchar(4000)
    EXEC sp_OAMethod @http, 'QuickGetStr', @html OUT, 'https://www.google.com/'
    EXEC sp_OAGetProperty @http, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @http, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @http
        RETURN
      END

    -- The 1st GET was not from cache:

    EXEC sp_OAGetProperty @http, 'LastFromCache', @iTmp0 OUT
    PRINT 'Fetched from cache: ' + @iTmp0

    -- Fetching again will cause the page to be delivered from our local cache.
    EXEC sp_OAMethod @http, 'QuickGetStr', @html OUT, 'https://www.google.com/'
    EXEC sp_OAGetProperty @http, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @http, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @http
        RETURN
      END

    -- The 2nd GET is from cache:

    EXEC sp_OAGetProperty @http, 'LastFromCache', @iTmp0 OUT
    PRINT 'Fetched from cache: ' + @iTmp0

    EXEC @hr = sp_OADestroy @http


END
GO