javaspring-boottomcatvaadinvaadin-flow

Why is MIME type of uploaded rar files application/octet-stream and how to change it to application/rar?

I am using Vaadin 24 with Spring Boot 3.x and Tomcat as servlet container. When I try to upload file with Vaadin component, Upload, MIME type of uploaded file is application/octet-stream when I expect application/rar with rar files (or any other equivalent like application/vnd.rar or application/x-rar-compressed). It might be also worth noting that I am using Firefox web browser on Windows OS.

I set up success listener to Upload component like this

    addSucceededListener(success -> {
                val receiver = (MemoryBuffer) this.getReceiver();
                val length = success.getContentLength();
                val fileName = success.getFileName();
                val mime = success.getMIMEType(); // mime type is application/octet-stream
                ...
            });

Why it is application/octet-stream and what can I change, so the MIME type is application/rar or any other equivalent, so I can better handle the file?

Solution

  • Whatever you see on the server side, is what your browser sends you.

    If you check the network-tab in your browser dev-tools, you will see a request for the upload of the file (basically http://localhost:8080/VAADIN/dynamic/resource/.../upload).

    If you inspect the payload, you will see, that this is multipart form-data and the part for the uploaded file contains a Content-Type and this is what Vaadin gives you for getMIMEType().

    Neither Spring nor Vaadin changes the value. And you are well advised to not trust whatever the client is sending here.