Slack will be deprecating the files.upload method for their API. In its place will be a new 3 step process. I’ve been successful executing Step 1 and Step 2 with Postman making calls to the Slack API. I’ve been successful executing Step 1 while making calls to the Slack API with my Java code. I have not been successful with Step 2 making calls to the Slack API with my Java code. I was hopeful to get some help with my Step 2 Java code.

Step 1: Make a HTTP GET Request to the files.getUploadURLExternal endpoint, passing the name of the file you intend to upload to Slack in a filename URL Query Parameter, and the size, in bytes, of the file in a length URL Query Parameter. This method is specifically documented here: https://api.slack.com/methods/files.getUploadURLExternal. The response you receive from files.getUploadURLExternal will include an upload_url value and a file_id argument

I was successful executing step 1 Slack API calls with Postman. You can see the proper query string parameters (Filename without path and size of file in bytes), the bear token and the response to the GET request.

Postman Step 1 successful

I was also successful executing step 1 Slack API calls with Java code. In the code, you can see the proper query string parameters (Filename without path and size of file in bytes), the bear token and the response to the GET request. The response consists of the upload_url and the file_id

 URL urlObj = new URL("https://slack.com/api/files.getUploadURLExternal?filename=namefile&length=40000");  //URL object is a reference/address to a resource on the network
 HttpsURLConnection connection =  (HttpsURLConnection) urlObj.openConnection();  //Using the URL object, establish the HttpsURLConnection so we can connect to the files.getUploadURLExternal API
 connection.setRequestMethod("GET");  //Specify what kind of request method this connection will have.  It could be GET.  It could be POST.  It could be DELETE. It could be PUT. 
 connection.setRequestProperty("Authorization", "Bearer " + botUserOAuthAccessToken); //The Slack token must be authorized in this way
 //When you send a request, you have to validate that the request was sent successfully and that you are able to get a valid response
 int responseCode = connection.getResponseCode(); //Define the response code as an integer
 System.out.println("Response CODE: "+responseCode);// Print the response code          
 if (responseCode == HttpsURLConnection.HTTP_OK)  //Test if you get a valid response code
  {
StringBuilder sb = new StringBuilder();  //Get the response that the API returns to us
Scanner scanner = new Scanner(connection.getInputStream()); //Use the scanner to read this response data from the InputStream
while (scanner.hasNext()) // StringBuilder is more efficient inside the while loop
  {
    sb.append(scanner.nextLine()); //Append the response to the StringBuilder
  }
 System.out.println(sb); //Print the string from the StringBuilder
 ObjectMapper objectMapper = new ObjectMapper(); //To manipuate the data, convert the string to a normal Java object
 JsonNode jsonNode = objectMapper.readTree(sb.toString()); //Convert Stringbuilder sb to JSON
 String urlupload = jsonNode.get("upload_url").asText(); //Grab the url_upload from the JSON
 System.out.println("url_upload: " + urlupload); //Print the url_upload value from the JSON
 System.out.println(jsonNode.get("upload_url"));
 String fileid = jsonNode.get("file_id").asText(); //Grab the file_id from the JSON
 System.out.println("file_id: " + fileid); //Print the file_id value from the JSON 

Here is the upload_url and file_id output from the code:
Response CODE: 200
{“ok”:true,”upload_url”:”https://files.slack.com/upload/v1/CwABAAAAWAoAAW3fBbTru-T7CgACF9bckBlvNhgMAAMLAAEAAAAJVDM2RVE4SFI2CwACAAAACVVERzZLUTVCNAsAAwAAAAtGMDc3NjJVTlgzNQAKAAQAAAAAAACcQAALAAIAAAAU_fItGMe4y90kNKMrXZEBrDuFQaMA”,”file_id”:”F07762UNX35″}
url_upload: https://files.slack.com/upload/v1/CwABAAAAWAoAAW3fBbTru-T7CgACF9bckBlvNhgMAAMLAAEAAAAJVDM2RVE4SFI2CwACAAAACVVERzZLUTVCNAsAAwAAAAtGMDc3NjJVTlgzNQAKAAQAAAAAAACcQAALAAIAAAAU_fItGMe4y90kNKMrXZEBrDuFQaMA
“https://files.slack.com/upload/v1/CwABAAAAWAoAAW3fBbTru-T7CgACF9bckBlvNhgMAAMLAAEAAAAJVDM2RVE4SFI2CwACAAAACVVERzZLUTVCNAsAAwAAAAtGMDc3NjJVTlgzNQAKAAQAAAAAAACcQAALAAIAAAAU_fItGMe4y90kNKMrXZEBrDuFQaMA”
file_id: F07762UNX35

Step 2: The response you receive from files.getUploadURLExternal will include an upload_url value and a file_id argument. Your next step is to make a HTTP POST Request to that upload_url passing the file that you wish to upload in the POST body, either as Raw Bytes or Multipart form encoded. This step is actually quite similar to the old files.upload approach. Whereas in that old approach, you were sending the file in a POST Request to the files.upload endpoint, in this new approach you are sending the file in a POST Request to upload_url you received.

I was successful executing Step 2 Slack API calls with Postman. I specified the upload_url, a bearer token, and I uploaded the file. When I clicked send, I received a 200 response OK.
Step 2 success Postman 1
Step 2 success Postman 2

Unfortunately, my Step 2 Slack API calls with Java code was not successful. I’ve setup everything the way I did in Postman. If you look at the code, the variable PathToReport represents the full path to my file. For example C:eclipseworkspaceTestGlobalNewsMavenRedesign202GlobalNewsMavenRedesign2019ExtentReportsGlobalNewsMavenRedesign2019Scripts.CheckGlobalNewsRunning05June202463152PM23.html
The variable urlupload represents the upload_url from step 1. I’ve specified a beare token, channel name and a multipart/form-data header

 HttpClient httpclient = HttpClientBuilder.create().disableContentCompression().build();  //Initiate the HttpClient to send the test execution results report to
 HttpPost httppost = new HttpPost(urlupload); //Post the Slack url
 MultipartEntityBuilder builder = MultipartEntityBuilder.create(); //Build the builder entity to host the test execution results report
 httppost.addHeader("Content-Type","multipart/form-data; boundary=--");
 FileBody fileBody = new FileBody(new File(PathToReport)); //Add the path of the test execution results report to the file body
 builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE); //Set up the builder structure to send the test execution results report and make sure it is browser compatible
 builder.addPart("file", fileBody); //Add the file containing the test execution results report to the builder structure
 builder.addTextBody("channels", channelName); //Add the channelName to the builder TextBody
 builder.addTextBody("token", botUserOAuthAccessToken); //Add the token to the builder TextBody
 httppost.setEntity(builder.build()); //Set the Entity for builder, post the test execution results report with all the builder components including file, channels and token
 HttpResponse response = null; //Set the HTTPResponse to null
 response = httpclient.execute(httppost); //The response is equal to the result of httppost
 HttpEntity result = response.getEntity(); //HTTPEntity Result equals the response of getEntity  
 System.out.println("R E S P O N S E :"+response);
 System.out.println("R E S U L T :"+result); 

Here is the error I get from this code: I get 400 Bad request. I’ve specified multipart/form-data as a Content-Type but the response mentions a Content-Type of text/plain. Is this a permission issue

R E S P O N S E :HttpResponseProxy{HTTP/1.1 400 Bad Request [Content-Type: text/plain, Content-Length: 21, Connection: keep-alive, x-backend: miata-prod-pdx-v2-546b549895-dq2jc, date: Fri, 07 Jun 2024 23:27:00 GMT, x-envoy-upstream-service-time: 2, x-edge-backend: miata, x-slack-edge-shared-secret-outcome: shared-secret, server: envoy, via: envoy-edge-pdx-xykemedc, 1.1 09331f0822fc98eebaf04130a83dbd44.cloudfront.net (CloudFront), X-Cache: Error from cloudfront, X-Amz-Cf-Pop: SEA73-P1, X-Amz-Cf-Id: 8Md2UWHCua6JA_5VWCguLvNloI25wVKo_kDXnLzxlE_ea-SZoak93w==, Cross-Origin-Resource-Policy: cross-origin] ResponseEntityProxy{[Content-Type: text/plain,Content-Length: 21,Chunked: false]}}

R E S U L T :ResponseEntityProxy{[Content-Type: text/plain,Content-Length: 21,Chunked: false]}

What do I have to fix in order to get the Step 2 success that I got with Postman. Am I missing a header. Is my file object wrong. I’m hoping that somebody with more Java experience can point out something that will help me. Thank you for any help you can give me.