How do I display validation errors about an uploaded multipart file using Spring MVC

Question

I have a Spring MVC application with a file upload form.

I would like to be able to display validation errors to a user if the upl

Answer 1

I got the answer to my question Spring community forums:

Here is the controller method:

@RequestMapping(method = RequestMethod.POST)
    public String processUploadWithModelAttribute(@ModelAttribute("myModelAttribute") final MyModelAttribute myModelAttribute, final BindingResult result, final Model model) throws IOException {
        String mimeType = determineMimeType(myModelAttribute.getFile().getBytes());
        if (mimeType.equalsIgnoreCase("application/pdf")){
            result.addError(new ObjectError("file", "pdf not accepted"));
        }
            return "fileupload";
    }

And the model attribute class:

public class MyModelAttribute {

    private MultipartFile file;

    public MultipartFile getFile() {
        return file;
    }

    public void setFile(MultipartFile file) {
        this.file = file;
    }
}

The idea is to put the MultipartFile into the ModelAttribute as an attribute.