What is the title of a Christian fiction book containing hero Prince Morningstar?

I really liked this book WAY back in middle school, where I lent it to a friend and never got it back. I want to read it again, but I can't remember anything but these few plot and character details: It was a Christian fiction book (probably allegorical) in which a male protagonist in a fictional old world ends up on a journey to find Prince Morningstar. The city he used to live in was governed by an evil prince. The main character ends up in a crisis situation where I think he is going to be arrested by his best friend. Those are the details I can remember. The cover of my edition had a dove on it, I think. If you can help, I'd appreciate it. Google is not giving me anything with this vagueness.