Uploading file using Jersey over RESTfull service and The resource configuration is not modifiable?

In order to use multipart in your Jersey application you need to register MultiPartFeature in your application, i.e.:

public class ApplicationConfig extends Application {

    public Set<Class<?>> getClasses() {
        final Set<Class<?>> resources = new HashSet<Class<?>>();

        // Add your resources.
        resources.add(UploadFileService.class);

        // Add additional features such as support for Multipart.
        resources.add(MultiPartFeature.class);

        return resources;
    }
}

For more information see Multipart section in the Jersey Users Guide.

For the second issue you’re facing try to restart the GlassFish server, I am not sure how NetBeans are reloading the Jersey app after a change (if this doesn’t help, please post your ApplicationConfig).