[undertow-dev] response-code handler bypasses configured error pages
Brad Wood
bdw429s at gmail.com
Fri Jul 3 16:55:47 EDT 2020
After a few hours of experimenting, I was able to answer a few of my own
questions, but not all of them.
- Yes, it is possible to contribute a custom handler to the predicate
language-- this is actually pretty sweet. I didn't realize just how
generic the parser was.
- In order to get "picked up", the builder class must be listed in the
*META-INF/services/io.undertow.server.handlers.builder.HandlerBuilder*
file
- That custom handler suggested by Stuart in the previous message ONLY
works if the predicate chain is wrapped "inside" the servlet initial
handler. Otherwise, the servletcontext classes are missing. This
unfortunately, makes it a no-go for me to be able to use.
The rest of my questions still stand however in so far as how I can
accomplish what I need.
During my experiments today, I also played with the error-file handler, but
it also is of no use. Since the response-code handler ends the exchange,
any error pages declared in the error file handler are never used!
error-file( response-codes={404},
file="C:\sandbox\predicatetest\custom404.html" )
path('/box.json') -> response-code(404)
I even tried creating a custom handler that sets the status code but
continues the exchange, but then that just serves the original file anyway,
which causes the error-file handler to do nothing since the response stream
is already started.
Thanks!
~Brad
*Developer Advocate*
*Ortus Solutions, Corp *
E-mail: brad at coldbox.org
ColdBox Platform: http://www.coldbox.org
Blog: http://www.codersrevolution.com
On Fri, Jul 3, 2020 at 12:02 PM Brad Wood <bdw429s at gmail.com> wrote:
> You probably need to write a custom one that looks like this (plus the
>> relevant predicate languge bits):
>
>
> Stuart, if I can branch the conversation here back to your idea of a
> custom handler for a bit...
>
> I'm still toying with this, and while the handleRequest() code you have
> makes perfect sense, I think I'm missing a lot of context on how you were
> suggesting this would work.
>
> - The code you put in your message-- were you suggesting that should
> be added to the Undertow core as a built in handler or just a custom class
> I would put in my project?
> - Would this handler require the predicates be processed downstream of
> the servlet initial handler in order to work? Because if so, that appears
> to be a no-go since handlers like the rewrite only appear to work upstream
> of the servlet
> - Is it possible to register custom handlers of my own creation with
> the predicate language or were you suggesting a handler that could only be
> manually configured? I'm familiar with the handler builder pattern that
> the built in handlers use, but I'm unclear on how builders get registered
> with the predicate handler parser.
> - Actually, I just reviewed the code again now and I see
> the loadHandlerBuilders() method in the PredicatedhandlersParser class
> appears to be scanning the classpath for builders. Interesting.... Does
> Undertow need to be loaded by the same class loader that loaded my custom
> handlers for this to work? I'm not super familiar with the ServiceLoader
> stuff
> - I'm not against building a custom handler that I ship alongside
> Undertow that provides what I'm looking for, but I'm still interested in
> having the conversation of how we can improve undertow's core offering.
>
> Thanks!
>
> ~Brad
>
> *Developer Advocate*
> *Ortus Solutions, Corp *
>
> E-mail: brad at coldbox.org
> ColdBox Platform: http://www.coldbox.org
> Blog: http://www.codersrevolution.com
>
>
>
> On Thu, Jul 2, 2020 at 7:01 PM Stuart Douglas <sdouglas at redhat.com> wrote:
>
>> Hmm, this is because the servlet status code is only triggered by a
>> sendError method, not by just setting the code.
>>
>> You probably need to write a custom one that looks like this (plus the
>> relevant predicate languge bits):
>>
>> public class SendErrorHandler implements HttpHandler {
>>
>> private final int code;
>>
>> public SendErrorHandler(int code) {
>> this.code = code;
>> }
>>
>> @Override
>> public void handleRequest(HttpServerExchange exchange) throws
>> Exception {
>> ServletRequestContext src =
>> exchange.getAttachment(ServletRequestContext.ATTACHMENT_KEY);
>> ((HttpServletResponse)src.getServletResponse()).sendError(code);
>> }
>> }
>>
>> Stuart
>>
>>
>>
>> On Fri, 3 Jul 2020 at 09:40, Brad Wood <bdw429s at gmail.com> wrote:
>>
>>> Thanks for the reply Stuart. I've tried this with no success, but
>>> perhaps I'm doing it wrong.
>>>
>>> List<PredicatedHandler> ph =
>>> PredicatedHandlersParser.parse(predicatesLines, _classLoader);
>>> servletBuilder.addOuterHandlerChainWrapper(next ->
>>> Handlers.predicates(ph,next));
>>>
>>> When the response-code handler fires, I still get no response body.
>>>
>>> On a related note, when I move the predicates into an outer handler
>>> chain wrapper, my default response listener also doesn't fire at all.
>>>
>>> On an unrelated train of thought, I've been trying to see if I can get
>>> the default response listener to automatically dispatch the correct error
>>> page, but that hasn't been going well either. If I don't use the outer
>>> handler chain idea, but try to capture the empty response in a default
>>> response listener, I can return a static message using the Sender class
>>>
>>> Sender sender = exchange.getResponseSender();
>>> sender.send(errorHTMLString);
>>>
>>> But if I try to run something this in my default response listener to
>>> invoke my error pages
>>>
>>> ServletRequestContext src =
>>> exchange.getAttachment(ServletRequestContext.ATTACHMENT_KEY);
>>> HttpServletResponseImpl response = src.getOriginalResponse();
>>> response.doErrorDispatch( exchange.getStatusCode(),
>>> exchange.getReasonPhrase() );
>>>
>>> Then it's as though nothing happens and I still get an empty response.
>>>
>>> Thanks!
>>>
>>> ~Brad
>>>
>>> *Developer Advocate*
>>> *Ortus Solutions, Corp *
>>>
>>> E-mail: brad at coldbox.org
>>> ColdBox Platform: http://www.coldbox.org
>>> Blog: http://www.codersrevolution.com
>>>
>>>
>>>
>>> On Thu, Jul 2, 2020 at 6:17 PM Stuart Douglas <sdouglas at redhat.com>
>>> wrote:
>>>
>>>> The predicate languages are executed before the Servler handlers, so
>>>> they won't be handled by Servlet error pages.
>>>>
>>>> If you are setting this all up programmatically you could use
>>>> io.undertow.servlet.api.DeploymentInfo#addOuterHandlerChainWrapper to setup
>>>> the predicate handler after the initial servlet one, which should mean that
>>>> the servlet error handling will handle the response code.
>>>>
>>>> Stuart
>>>>
>>>> On Fri, 3 Jul 2020 at 08:25, Brad Wood <bdw429s at gmail.com> wrote:
>>>>
>>>>> When I configure an error page similar to this:
>>>>>
>>>>> servletBuilder.addErrorPage( new ErrorPage( "404.html", 404));
>>>>>
>>>>> This works great when I hit a path in my browser that doesn't exist.
>>>>> The contents of the *404.html* file is served with a response code of
>>>>> *404*.
>>>>>
>>>>> However, if I also use the predicate language to define something like:
>>>>>
>>>>> path(/box.json)->response-code(404)
>>>>>
>>>>> and then I hit *localhost/box.json* in my browser, I get a *404*
>>>>> status code but with no response body.
>>>>>
>>>>> - The docs say the response-code handler ends the exchange, but
>>>>> should it still respect the error pages?
>>>>> - How can I modify my use of Undertow to respect the error pages
>>>>> when using the response-code handler?
>>>>> - I've seen in the docs the ability to have a
>>>>> *addDefaultResponseListener()* but I'm not sure if it is the
>>>>> correct solution for this, nor how I would access the error page
>>>>> configuration dynamically as to not need to duplicate my work.
>>>>>
>>>>> Thanks!
>>>>>
>>>>> ~Brad
>>>>>
>>>>> *Developer Advocate*
>>>>> *Ortus Solutions, Corp *
>>>>>
>>>>> E-mail: brad at coldbox.org
>>>>> ColdBox Platform: http://www.coldbox.org
>>>>> Blog: http://www.codersrevolution.com
>>>>>
>>>>> _______________________________________________
>>>>> undertow-dev mailing list
>>>>> undertow-dev at lists.jboss.org
>>>>> https://lists.jboss.org/mailman/listinfo/undertow-dev
>>>>
>>>>
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