How Can I Restrict File Uploads to Only PDF in a Process Instance?

Camunda 7 Topics Discussion & Questions
1

Hi everyone,

I’m currently facing an issue where all file types are being allowed for upload in a process instance, and I need to restrict it so that only PDF files can be uploaded.

Is there a way to configure this restriction or enforce only PDF uploads in the process instance?

Any advice or suggestions on how to achieve this would be greatly appreciated!

2

Can you simply restict this in the front end?

3

The accept=".pdf" attribute ensures only PDF files are selectable.
this will help on FE side for you.

public class FileValidationDelegate implements JavaDelegate {

@Override
public void execute(DelegateExecution execution) throws Exception {
    byte[] fileContent = (byte[]) execution.getVariable("uploadedFile");
    String fileName = (String) execution.getVariable("fileName");

    // Check file extension
    if (!fileName.endsWith(".pdf")) {
        throw new IllegalArgumentException("Only PDF files are allowed!");
    }

    // Optionally, check file signature (magic number) for stricter validation
    String magicNumber = Base64.getEncoder().encodeToString(fileContent).substring(0, 4);
    if (!magicNumber.equals("25504446")) { // PDF Magic Number: %PDF
        throw new IllegalArgumentException("Uploaded file is not a valid PDF!");
    }
}

}

In your BPMN model, include a condition or validation step where the process checks the uploaded file type. This can be done using an exclusive gateway or a service task.