JPro CORS Issue #205

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1. FlorianKirmaier commented on Mar 25, 2026

   

   FlorianKirmaier

   on Mar 25, 2026

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   Can you share some details?
   I assume you try to access the REST-Api from another tab which has a different domain?

   You should be able to overwrite headers with the ServerAPI.
   We might also offer a way to remove all default headers.
   We will probably soon provide a way, to configure CORS more detailed.
2. nyzzik commented on Mar 25, 2026

   

   nyzzik

   on Mar 25, 2026

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   @FlorianKirmaier

   Yes, I am trying to access the REST-Api from another tab on a different domain however when i try to it complains about CORS. I tried setting the headers manually with the ServerAPI but then it throws an error on the client I am trying to do the request from saying that there is multiple instances of that header in the request. Get requests work fine, anything else though throws the CORS error.
   Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8081/signals?. (Reason: Multiple CORS header ‘Access-Control-Allow-Origin’ not allowed).

   headers.put("Access-Control-Allow-Origin", "*");
   headers.put("Access-Control-Allow-Methods", "*");
   headers.put("Access-Control-Allow-Headers", "*");

   This is how I am setting the headers and then I am passing the headers HashMap to each of the Responses.

   public static void main(String[] args) {
       gson = new GsonBuilder()
           .excludeFieldsWithModifiers(Modifier.PRIVATE, Modifier.STATIC, Modifier.TRANSIENT, Modifier.VOLATILE)
           .create();
       headers.put("Access-Control-Allow-Origin", "*");
       headers.put("Access-Control-Allow-Methods", "*");
       headers.put("Access-Control-Allow-Headers", "*");
       System.out.println("HMI API is running...");
       ServerAPI.getServerAPI().addRequestHandler(request -> {
           switch (request.getPath()) {
               case PATH_TEST:
                   return textResponse("Test response");
               case PATH_RESTART:
                   DataVAC.restartProg();
                   return textResponse("Restart command executed");
               case PATH_SIGNALS:
                   switch (request.getMethod()) {
                       case "GET":
                           return handleSignalsRequest(request);
                       case "POST":
                           return handleSignalPostRequest(request);
                       default:
                           break;
                   }
               default:
                   return Response.empty();
           }
   
       });
   }
   
   private static Response handleSignalPostRequest(Request request) {
       return Response.of("POST endpoint for signal updates is not implemented yet.".getBytes(StandardCharsets.UTF_8), "text/plain", 501, headers);
   }
3. nyzzik commented on Mar 25, 2026

   

   nyzzik

   on Mar 25, 2026

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   I realized that I was not handling the OPTIONS method.
4. nyzzik

   closed this as completedon Mar 25, 2026