VB.NET Requires Chilkat v11.0.0+

REST Follow Redirects

See more REST Examples

Demonstrates how to follow a 302/303 redirect response. VB.NET

Dim success As Boolean = False

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

Dim rest As New Chilkat.Rest

Dim bTls As Boolean = True
Dim port As Integer = 443
Dim bAutoReconnect As Boolean = True
success = rest.Connect("chilkatsoft.com",port,bTls,bAutoReconnect)
If (success = False) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


'  Send a POST to a URL that will respond with a 302 redirect..
rest.AddQueryParam("firstName","John")
rest.AddQueryParam("lastName","Doe")
Dim responseText As String = rest.FullRequestFormUrlEncoded("POST","/echoPost302.asp")
If (rest.LastMethodSuccess = False) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


Dim statusCode As Integer = rest.ResponseStatusCode

'  Examine the response status code
If (statusCode < 300) Then
    Debug.WriteLine("Not a redirect.")
    Debug.WriteLine(responseText)
    Exit Sub
End If


If (statusCode > 399) Then
    Debug.WriteLine("Error response: Status code = " & statusCode)
    Debug.WriteLine(responseText)
    Exit Sub
End If


Debug.WriteLine("Redirect status code = " & statusCode)

'  The response header will contain a Location field with the redirect URL, such as this:
'  Location: http://www.chilkatsoft.com/echoPostFinal.asp

'  The response status code determines how the client should behave.
'  Here are some common possibilities:

'  301: Moved Permanently
'  This and all future requests should be directed to the given URI.  (Keep the original HTTP method for the redirect.  In this case, the 
'  original request was a POST, so we POST to the redirect URL.)

'  302: Found (aka Object Moved aka Moved Temporarily)
'  This is the most popular redirect code, but also an example of industrial practice contradicting the standard. HTTP/1.0 specification (RFC 1945 ) required the client
'  to perform a temporary redirect (the original describing phrase was �Moved Temporarily�), but popular browsers implemented it as a 303 See Other. Therefore, HTTP/1.1
'  added status codes 303 and 307 to disambiguate between the two behaviors. However, the majority of Web applications and frameworks still use the 302 status code
'  as if it were the 303.

'  303: See Other
'  The response to the request can be found under another URI using a GET method. When received in response to a PUT, it should be assumed that the server has
'  received the data and the redirect should be issued with a separate GET message.

'  307: Temporary Redirect
'  In this occasion, the request should be repeated with another URI, but future requests can still use the original URI. In contrast to 303, the request method
'  should not be changed when reissuing the original request. For instance, a POST request must be repeated using another POST request.

Debug.WriteLine(rest.ResponseHeader)

'  Get the redirect URL
Dim urlStr As String = rest.LastRedirectUrl
If (rest.LastMethodSuccess = False) Then
    Debug.WriteLine("No Location header found for redirect.")
    Exit Sub
End If

Dim redirectUrl As New Chilkat.Url
redirectUrl.ParseUrl(urlStr)

'  Prep for the redirect..
rest.ClearAllParts()

'  Disconnect and re-connect.  
'  (This can be skipped if both the host and SSL/TLS conditions are the same.)
rest.Disconnect(100)
success = rest.Connect(redirectUrl.Host,redirectUrl.Port,redirectUrl.Ssl,bAutoReconnect)
If (success = False) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


If ((statusCode = 301) Or (statusCode = 307)) Then
    '  Redirect using a POST, sending the same params to the new destination
    rest.AddQueryParam("firstName","John")
    rest.AddQueryParam("lastName","Doe")
    responseText = rest.FullRequestFormUrlEncoded("POST",redirectUrl.Path)
    If (rest.LastMethodSuccess = False) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


End If


If ((statusCode = 302) Or (statusCode = 303)) Then
    '  Redirect using a GET, sending the query params found in the redirect URL.
    responseText = rest.FullRequestFormUrlEncoded("GET",redirectUrl.PathWithQueryParams)
    If (rest.LastMethodSuccess = False) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


End If


'  Show the final status code and the response text.
Debug.WriteLine("Final status code = " & rest.ResponseStatusCode)

Debug.WriteLine("Final response text (HTML, XML, JSON, or whatever..)")
Debug.WriteLine(responseText)