Question

I am creating a custom HTTP 500 error template. Why is it Django shows it when i raise an exception and not when I return HttpResponseServerError (I just get the default browser 500 error)? I find this behaviour strange…

Answer 1

The HttpResponseServerError inherits from HttpResponse and is actually quite simple:

class HttpResponseServerError(HttpResponse):
    status_code = 500

So let’s look at the HttpResponse constructor:

def __init__(self, content='', *args, **kwargs):
    super(HttpResponse, self).__init__(*args, **kwargs)
    # Content is a bytestring. See the `content` property methods.
    self.content = content

As you can see by default content is empty.

Now, let’s take a look at how it is called by Django itself (an excerpt from django.views.defaults):

def server_error(request, template_name='500.html'):
    """
    500 error handler.

    Templates: :template:`500.html`
    Context: None
    """
    try:
        template = loader.get_template(template_name)
    except TemplateDoesNotExist:
        return http.HttpResponseServerError('<h1>Server Error (500)</h1>')
    return http.HttpResponseServerError(template.render(Context({})))

As you can see when you produce a server error, the template named 500.html is used, but when you simply return HttpResponseServerError the content is empty and the browser falls back to it’s default page.