(SQL Server) HTTP GET -- Read Response from Stream

Demonstrates how to send an HTTP GET for a web page, and then read the response from a Stream. The purpose is to fulfill a situation such as the following: "I have a URL and just want the <head> </head> portion of the HTML. This would avoid having to download a potentially enormous web page just to get at header information, such as the <styles>."

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

-- 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
    DECLARE @iTmp1 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- This example requires the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @rest int
    -- Use "Chilkat_9_5_0.Rest" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Rest', @rest OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- In this example, we'll get the web page at http://www.nytimes.com/pages/business/index.html
    -- The domain is "www.nytimes.com", and the path is "/pages/business/index.html"

    -- If we have only the full URL to begin with, it can be loaded into the Chilkat URL object to
    -- access the parts:
    DECLARE @url int
    -- Use "Chilkat_9_5_0.Url" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Url', @url OUT

    DECLARE @success int
    EXEC sp_OAMethod @url, 'ParseUrl', @success OUT, 'http://www.nytimes.com/pages/business/index.html'

    DECLARE @bAutoReconnect int
    SELECT @bAutoReconnect = 1
    DECLARE @success int
    EXEC sp_OAGetProperty @url, 'Host', @sTmp0 OUT
    EXEC sp_OAGetProperty @url, 'Port', @iTmp0 OUT
    EXEC sp_OAGetProperty @url, 'Ssl', @iTmp1 OUT
    EXEC sp_OAMethod @rest, 'Connect', @success OUT, @sTmp0, @iTmp0, @iTmp1, @bAutoReconnect

    -- Send the GET request (This sends the GET request, but does not read the response.)
    EXEC sp_OAGetProperty @url, 'Path', @sTmp0 OUT
    EXEC sp_OAMethod @rest, 'SendReqNoBody', @success OUT, 'GET', @sTmp0
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @url
        RETURN
      END

    -- Read the response header.
    DECLARE @responseStatusCode int
    EXEC sp_OAMethod @rest, 'ReadResponseHeader', @responseStatusCode OUT
    IF @responseStatusCode < 0
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @url
        RETURN
      END


    PRINT 'Response status code = ' + @responseStatusCode

    -- We expect a 200 response status.
    IF @responseStatusCode <> 200
      BEGIN

        -- If the response status code is not 200, we could check for a redirect status code and 
        -- then follow it, read the entire response (as shown here), or just call rest.Disconnect
        DECLARE @errResponse nvarchar(4000)
        EXEC sp_OAMethod @rest, 'ReadRespBodyString', @errResponse OUT
        EXEC sp_OAGetProperty @rest, 'LastMethodSuccess', @iTmp0 OUT
        IF @iTmp0 <> 1
          BEGIN
            EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
          END
        ELSE
          BEGIN

            PRINT @errResponse
          END

        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @url
        RETURN
      END

    DECLARE @bodyStream int
    -- Use "Chilkat_9_5_0.Stream" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Stream', @bodyStream OUT

    -- Set a 10 second read timeout for the stream. 
    -- (Give up if no data arrives within 10 seconds after calling a read method.)
    EXEC sp_OASetProperty @bodyStream, 'ReadTimeoutMs', 10000

    -- Create a background thread task to read the response body (which feeds
    -- it to the bodyStream object.)
    DECLARE @readResponseBodyTask int
    EXEC sp_OAMethod @rest, 'ReadRespBodyStreamAsync', @readResponseBodyTask OUT, @bodyStream, 1

    -- Start the task. 
    EXEC sp_OAMethod @readResponseBodyTask, 'Run', @success OUT

    -- Read the HTTP response body until the "</head>" is seen, or until
    -- the end-of-stream is reached.

    DECLARE @sbBody int
    -- Use "Chilkat_9_5_0.StringBuilder" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbBody OUT

    DECLARE @exitLoop int
    SELECT @exitLoop = 0
    EXEC sp_OAGetProperty @bodyStream, 'EndOfStream', @iTmp0 OUT
    WHILE Not @exitLoop and (@iTmp0 <> 1)
      BEGIN

        DECLARE @bodyText nvarchar(4000)
        EXEC sp_OAMethod @bodyStream, 'ReadString', @bodyText OUT
        EXEC sp_OAGetProperty @bodyStream, 'LastMethodSuccess', @iTmp0 OUT
        IF @iTmp0 = 1
          BEGIN
            EXEC sp_OAMethod @sbBody, 'Append', @success OUT, @bodyText
            EXEC sp_OAMethod @sbBody, 'Contains', @iTmp0 OUT, '</head>', 0
            IF @iTmp0
              BEGIN
                SELECT @exitLoop = 1
              END
          END
        ELSE
          BEGIN
            SELECT @exitLoop = 1
          END

      END

    -- Cancel the remainder of the task...
    EXEC sp_OAMethod @readResponseBodyTask, 'Cancel', @success OUT

    EXEC @hr = sp_OADestroy @readResponseBodyTask

    -- Ensure we're disconnected from the server.
    DECLARE @maxWaitMs int
    SELECT @maxWaitMs = 50
    EXEC sp_OAMethod @rest, 'Disconnect', @success OUT, @maxWaitMs


    PRINT '----'
    EXEC sp_OAMethod @sbBody, 'GetAsString', @sTmp0 OUT
    PRINT @sTmp0

    PRINT '----'

    PRINT 'Successfully received the body up to the desired point.'

    EXEC @hr = sp_OADestroy @rest
    EXEC @hr = sp_OADestroy @url
    EXEC @hr = sp_OADestroy @bodyStream
    EXEC @hr = sp_OADestroy @sbBody


END
GO