Plack::Middleware::HTTPExceptions - Catch HTTP exceptions


  use HTTP::Exception;

  my $app = sub {
      # ...

  builder {
      enable "HTTPExceptions", rethrow => 1;


Plack::Middleware::HTTPExceptions is a PSGI middleware component to catch exceptions from applications that can be translated into HTTP status codes.

Your application is supposed to throw an object that implements a code method which returns the HTTP status code, such as 501 or 404. This middleware catches them and creates a valid response out of the code. If the code method returns a code that is not an HTTP redirect or error code (3xx, 4xx, or 5xx), the exception will be rethrown.

The exception object may also implement as_string or overload stringification to represent the text of the error. The text defaults to the status message of the error code, such as Service Unavailable for 503.

Finally, the exception object may implement as_psgi, and the result of this will be returned directly as the PSGI response.

If the code is in the 3xx range and the exception implements the 'location' method (HTTP::Exception::3xx does), the Location header will be set in the response, so you can do redirects this way.

There are CPAN modules HTTP::Exception and HTTP::Throwable, and they are perfect to throw from your application to let this middleware catch and display, but you can also implement your own exception class to throw.

If the thrown exception is not an object that implements either a code or an as_psgi method, a 500 error will be returned, and the exception is printed to the psgi.errors stream. Alternatively, you can pass a true value for the rethrow parameter for this middleware, and the exception will instead be rethrown. This is enabled by default when PLACK_ENV is set to development, so that the StackTrace middleware can catch it instead.


Tatsuhiko Miyagawa


paste.httpexceptions HTTP::Exception HTTP::Throwable