PowerBuilder

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>."

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integer li_rc
integer li_Success
oleobject loo_Rest
oleobject loo_Url
integer li_BAutoReconnect
integer li_ResponseStatusCode
string ls_ErrResponse
oleobject loo_BodyStream
oleobject loo_ReadResponseBodyTask
oleobject loo_SbBody
integer li_ExitLoop
string ls_BodyText
integer li_MaxWaitMs

li_Success = 0

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loo_Rest = create oleobject
li_rc = loo_Rest.ConnectToNewObject("Chilkat.Rest")
if li_rc < 0 then
    destroy loo_Rest
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// 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:
loo_Url = create oleobject
li_rc = loo_Url.ConnectToNewObject("Chilkat.Url")

loo_Url.ParseUrl("http://www.nytimes.com/pages/business/index.html")

li_BAutoReconnect = 1
li_Success = loo_Rest.Connect(loo_Url.Host,loo_Url.Port,loo_Url.Ssl,li_BAutoReconnect)

// Send the GET request (This sends the GET request, but does not read the response.)
li_Success = loo_Rest.SendReqNoBody("GET",loo_Url.Path)
if li_Success <> 1 then
    Write-Debug loo_Rest.LastErrorText
    destroy loo_Rest
    destroy loo_Url
    return
end if

// Read the response header.
li_ResponseStatusCode = loo_Rest.ReadResponseHeader()
if li_ResponseStatusCode < 0 then
    Write-Debug loo_Rest.LastErrorText
    destroy loo_Rest
    destroy loo_Url
    return
end if

Write-Debug "Response status code = " + string(li_ResponseStatusCode)

// We expect a 200 response status.
if li_ResponseStatusCode <> 200 then

    // 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
    ls_ErrResponse = loo_Rest.ReadRespBodyString()
    if loo_Rest.LastMethodSuccess <> 1 then
        Write-Debug loo_Rest.LastErrorText
    else
        Write-Debug ls_ErrResponse
    end if

    destroy loo_Rest
    destroy loo_Url
    return
end if

loo_BodyStream = create oleobject
li_rc = loo_BodyStream.ConnectToNewObject("Chilkat.Stream")

// Set a 10 second read timeout for the stream. 
// (Give up if no data arrives within 10 seconds after calling a read method.)
loo_BodyStream.ReadTimeoutMs = 10000

// Create a background thread task to read the response body (which feeds
// it to the bodyStream object.)
loo_ReadResponseBodyTask = loo_Rest.ReadRespBodyStreamAsync(loo_BodyStream,1)

// Start the task. 
li_Success = loo_ReadResponseBodyTask.Run()

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

loo_SbBody = create oleobject
li_rc = loo_SbBody.ConnectToNewObject("Chilkat.StringBuilder")

li_ExitLoop = 0
do while not li_ExitLoop AND (loo_BodyStream.EndOfStream <> 1)

    ls_BodyText = loo_BodyStream.ReadString()
    if loo_BodyStream.LastMethodSuccess = 1 then
        loo_SbBody.Append(ls_BodyText)
        if loo_SbBody.Contains("</head>",0) then
            li_ExitLoop = 1
        end if

    else
        li_ExitLoop = 1
    end if

loop

// Cancel the remainder of the task...
loo_ReadResponseBodyTask.Cancel()

destroy loo_ReadResponseBodyTask

// Ensure we're disconnected from the server.
li_MaxWaitMs = 50
loo_Rest.Disconnect(li_MaxWaitMs)

Write-Debug "----"
Write-Debug loo_SbBody.GetAsString()
Write-Debug "----"
Write-Debug "Successfully received the body up to the desired point."


destroy loo_Rest
destroy loo_Url
destroy loo_BodyStream
destroy loo_SbBody