DataFlex
DataFlex
Firebase Receive Server-Sent Events (text/event-stream)
See more Firebase Examples
Demonstrates how to start receiving server-sent events and update your JSON database with each event.Chilkat DataFlex Downloads
Use ChilkatAx-win32.pkg
Procedure Test
Boolean iSuccess
Handle hoFac
String sAccessToken
Handle hoRest
Variant vAuthGoogle
Handle hoAuthGoogle
String sResponseBody
String sUrlStr
Handle hoUrl
Handle hoRest2
Integer iResponseStatusCode
Handle hoJsonDb
Variant vEventStream
Handle hoEventStream
Handle hoSse
Variant vTask
Handle hoTask
Integer iCount
String sEventStr
String sTemp1
String sTemp2
Integer iTemp1
Boolean bTemp1
Move False To iSuccess
// Demonstrates how to begin receiving server-sent events, and to update
// your JSON database for each event.
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.
// This example assumes a JWT authentication token, if required, has been previously obtained.
// See Get Firebase Access Token from JSON Service Account Private Key for sample code.
// Load the previously obtained Firebase access token into a string.
Get Create (RefClass(cComCkFileAccess)) To hoFac
If (Not(IsComObjectCreated(hoFac))) Begin
Send CreateComObject of hoFac
End
Get ComReadEntireTextFile Of hoFac "qa_data/tokens/firebaseToken.txt" "utf-8" To sAccessToken
Get ComLastMethodSuccess Of hoFac To bTemp1
If (bTemp1 = False) Begin
Get ComLastErrorText Of hoFac To sTemp1
Showln sTemp1
Procedure_Return
End
Get Create (RefClass(cComChilkatRest)) To hoRest
If (Not(IsComObjectCreated(hoRest))) Begin
Send CreateComObject of hoRest
End
// Make the initial connection (without sending a request yet).
// Once connected, any number of requests may be sent. It is not necessary to explicitly
// call Connect before each request.
Get ComConnect Of hoRest "chilkat.firebaseio.com" 443 True True To iSuccess
If (iSuccess = False) Begin
Get ComLastErrorText Of hoRest To sTemp1
Showln sTemp1
Procedure_Return
End
Get Create (RefClass(cComChilkatAuthGoogle)) To hoAuthGoogle
If (Not(IsComObjectCreated(hoAuthGoogle))) Begin
Send CreateComObject of hoAuthGoogle
End
Set ComAccessToken Of hoAuthGoogle To sAccessToken
Get pvComObject of hoAuthGoogle to vAuthGoogle
Get ComSetAuthGoogle Of hoRest vAuthGoogle To iSuccess
Get ComAddHeader Of hoRest "Accept" "text/event-stream" To iSuccess
Get ComAddHeader Of hoRest "Cache-Control" "no-cache" To iSuccess
Get ComFullRequestNoBody Of hoRest "GET" "/.json" To sResponseBody
// A 307 redirect response is expected.
Get ComResponseStatusCode Of hoRest To iTemp1
If (iTemp1 <> 307) Begin
Get ComResponseStatusCode Of hoRest To iTemp1
Showln "Unexpected response code: " iTemp1
Showln sResponseBody
Showln "Failed."
Procedure_Return
End
// Get the redirect URL
Get ComLastRedirectUrl Of hoRest To sUrlStr
Get Create (RefClass(cComChilkatUrl)) To hoUrl
If (Not(IsComObjectCreated(hoUrl))) Begin
Send CreateComObject of hoUrl
End
Get ComParseUrl Of hoUrl sUrlStr To iSuccess
Get ComHost Of hoUrl To sTemp1
Showln "redirect URL domain: " sTemp1
Get ComPath Of hoUrl To sTemp1
Showln "redirect URL path: " sTemp1
Get ComQuery Of hoUrl To sTemp1
Showln "redirect URL query params: " sTemp1
Get ComPathWithQueryParams Of hoUrl To sTemp1
Showln "redirect URL path with query params: " sTemp1
// Our text/event-stream will be obtained from the redirect URL...
Get Create (RefClass(cComChilkatRest)) To hoRest2
If (Not(IsComObjectCreated(hoRest2))) Begin
Send CreateComObject of hoRest2
End
Get ComHost Of hoUrl To sTemp1
Get ComConnect Of hoRest2 sTemp1 443 True True To iSuccess
If (iSuccess <> True) Begin
Get ComLastErrorText Of hoRest2 To sTemp1
Showln sTemp1
Procedure_Return
End
Get ComAddHeader Of hoRest2 "Accept" "text/event-stream" To iSuccess
Get ComAddHeader Of hoRest2 "Cache-Control" "no-cache" To iSuccess
// Add the redirect query params to the request
Get ComQuery Of hoUrl To sTemp1
Get ComAddQueryParams Of hoRest2 sTemp1 To iSuccess
// In our case, we don't actually need the auth query param,
// so remove it.
Get ComRemoveQueryParam Of hoRest2 "auth" To iSuccess
// Send the request. (We are only sending the request here.
// We are not yet getting the response because the response
// will be a text/event-stream.)
Get ComPath Of hoUrl To sTemp1
Get ComSendReqNoBody Of hoRest2 "GET" sTemp1 To iSuccess
If (iSuccess <> True) Begin
Get ComLastErrorText Of hoRest2 To sTemp1
Showln sTemp1
Procedure_Return
End
// Read the response header.
// We want to first get the response header to see if it's a successful
// response status code. If not, then the response will not be a text/event-stream
// and we should read the response body normally.
Get ComReadResponseHeader Of hoRest2 To iResponseStatusCode
If (iResponseStatusCode < 0) Begin
Get ComLastErrorText Of hoRest2 To sTemp1
Showln sTemp1
Procedure_Return
End
// If successful, a 200 response code is expected.
// If the reponse code is not 200, then read the response body and fail..
If (iResponseStatusCode <> 200) Begin
Showln "Response Code: " iResponseStatusCode
Get ComResponseStatusText Of hoRest2 To sTemp1
Showln "Response Status Text: " sTemp1
Get ComResponseHeader Of hoRest2 To sTemp1
Showln "Response Header: " sTemp1
Get ComReadRespBodyString Of hoRest2 To sResponseBody
Get ComLastMethodSuccess Of hoRest2 To bTemp1
If (bTemp1 = True) Begin
Showln "Error Response Body: " sResponseBody
End
Showln "Failed."
Procedure_Return
End
// For this example, our JSON database will be empty at the beginning.
// The incoming events (put and patch) will be applied to this database.
Get Create (RefClass(cComChilkatJsonObject)) To hoJsonDb
If (Not(IsComObjectCreated(hoJsonDb))) Begin
Send CreateComObject of hoJsonDb
End
// Make sure to set the JSON path delimiter to "/". The default is "." and this
// is not compatible with Firebase paths.
Set ComDelimiterChar Of hoJsonDb To "/"
// At this point, we've received the response header. Now it's time to begin
// receiving the event stream. We'll start a background thread to read the
// stream. (Our main application (foreground) thread can cancel it at any time.)
// While receiving in the background thread, our foreground thread can read the stream
// as it desires..
Get Create (RefClass(cComChilkatStream)) To hoEventStream
If (Not(IsComObjectCreated(hoEventStream))) Begin
Send CreateComObject of hoEventStream
End
// This sse object will be used as a helper to parse the server-sent event stream.
Get Create (RefClass(cComChilkatServerSentEvent)) To hoSse
If (Not(IsComObjectCreated(hoSse))) Begin
Send CreateComObject of hoSse
End
Get pvComObject of hoEventStream to vEventStream
Get ComReadRespBodyStreamAsync Of hoRest2 vEventStream True To vTask
If (IsComObject(vTask)) Begin
Get Create (RefClass(cComChilkatTask)) To hoTask
Set pvComObject Of hoTask To vTask
End
Get ComRun Of hoTask To iSuccess
// For this example, we'll just read a few events, and then cancel the
// async task.
Move 0 To iCount
While ((iCount < 3) And ((ComFinished(hoTask)) = False))
// Get the next event, which is a series of text lines ending with
// a blank line.
// Note: This method blocks the calling thread until a message arrives.
// a program might instead periodically check the availability of
// data via the stream's DataAvailable property, and then do the read.
// An alternative to writing a while loop to read the event stream
// would be to setup some sort of timer event in your program (using whatever timer functionality
// is provided in a programming language/environment), to periodically check the eventStream's
// DataAvailable property and consume the incoming event.
Get ComReadUntilMatch Of hoEventStream (character(13)) + (character(10)) + (character(13)) + (character(10)) To sEventStr
Get ComLastMethodSuccess Of hoEventStream To bTemp1
If (bTemp1 <> True) Begin
Get ComLastErrorText Of hoEventStream To sTemp1
Showln sTemp1
// Force the loop to exit by setting the count to a high number.
Move 99999 To iCount
End
Else Begin
Showln "Event: [" sEventStr "]"
// We have an event. Let's update our local copy of the JSON database.
Get ComLoadEvent Of hoSse sEventStr To iSuccess
If (iSuccess <> True) Begin
Showln "Failed to load sse event: " sEventStr
End
Else Begin
// Now we can easily access the event name and data, and apply it to our JSON database:
Get ComEventName Of hoSse To sTemp1
Get ComData Of hoSse To sTemp2
Get ComFirebaseApplyEvent Of hoJsonDb sTemp1 sTemp2 To iSuccess
If (iSuccess <> True) Begin
Get ComEventName Of hoSse To sTemp1
Get ComData Of hoSse To sTemp2
Showln "Failed to apply event: " sTemp1 ": " sTemp2
End
Else Begin
Get ComEventName Of hoSse To sTemp1
Get ComData Of hoSse To sTemp2
Showln "Successfully applied event: " sTemp1 ": " sTemp2
End
End
End
Move (iCount + 1) To iCount
Loop
// Make sure the background task is cancelled if still running.
Get ComCancel Of hoTask To iSuccess
Send Destroy of hoTask
// Examine the JSON database after applying events..
Set ComEmitCompact Of hoJsonDb To False
Showln "----"
Get ComEmit Of hoJsonDb To sTemp1
Showln sTemp1
End_Procedure