Refs #26601 -- Refactored BaseHandler to prepare for new-style middleware.

django/middleware/exception.py

+from __future__ import unicode_literals
+
+import logging
+import sys
+
+from django.conf import settings
+from django.core import signals
+from django.core.exceptions import PermissionDenied, SuspiciousOperation
+from django.http import Http404
+from django.http.multipartparser import MultiPartParserError
+from django.urls import get_resolver, get_urlconf
+from django.utils.encoding import force_text
+from django.views import debug
+
+logger = logging.getLogger('django.request')
+
+
+class ExceptionMiddleware(object):
+    """
+    Convert selected exceptions to HTTP responses.
+
+    For example, convert Http404 to a 404 response either through handler404
+    or through the debug view if settings.DEBUG=True. To ensure that
+    exceptions raised by other middleware are converted to the appropriate
+    response, this middleware is always automatically applied as the outermost
+    middleware.
+    """
+    def __init__(self, get_response, handler=None):
+        from django.core.handlers.base import BaseHandler
+        self.get_response = get_response
+        self.handler = handler or BaseHandler()
+
+    def __call__(self, request):
+        try:
+            response = self.get_response(request)
+        except Http404 as exc:
+            if settings.DEBUG:
+                response = debug.technical_404_response(request, exc)
+            else:
+                response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 404, exc)
+
+        except PermissionDenied as exc:
+            logger.warning(
+                'Forbidden (Permission denied): %s', request.path,
+                extra={'status_code': 403, 'request': request},
+            )
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 403, exc)
+
+        except MultiPartParserError as exc:
+            logger.warning(
+                'Bad request (Unable to parse request body): %s', request.path,
+                extra={'status_code': 400, 'request': request},
+            )
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 400, exc)
+
+        except SuspiciousOperation as exc:
+            # The request logger receives events for any problematic request
+            # The security logger receives events for all SuspiciousOperations
+            security_logger = logging.getLogger('django.security.%s' % exc.__class__.__name__)
+            security_logger.error(
+                force_text(exc),
+                extra={'status_code': 400, 'request': request},
+            )
+            if settings.DEBUG:
+                return debug.technical_500_response(request, *sys.exc_info(), status_code=400)
+
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 400, exc)
+
+        except SystemExit:
+            # Allow sys.exit() to actually exit. See tickets #1023 and #4701
+            raise
+
+        except Exception:  # Handle everything else.
+            # Get the exception info now, in case another exception is thrown later.
+            signals.got_request_exception.send(sender=self.handler.__class__, request=request)
+            response = self.handler.handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
+
+        return response