play 404 default error handler

[abhinandc3]

does anybody know the error handler for 404

I am trying to understand how it works internally. for 2.5
I added a breakpoint to the methods in class
https://www.playframework.com/documentation/2.5.x/api/java/play/http/DefaultHttpErrorHandler.html
its not getting executed

can someone pls guide what method is getting invoked by default for 404 methods

[mkurz]

I can't speak for Play 2.5 because we don't support that anymore and I am not willing to take a look how it worked back then. But as of 2.8.x you find more information in the here (config play.http.errorHandler), maybe you need to set the breakpoint in the class play.api.http.DefaultHttpErrorHandler (note the api)?

playframework/core/play/src/main/resources/reference.conf

Lines 49 to 57 in 6aa434b

	# The error handler.
	# Used by Play's built in DI support to locate and bind an error handler. Must be one of the following:
	# - A FQCN that implements play.api.http.HttpErrorHandler (Scala).
	# - A FQCN that implements play.http.HttpErrorHandler (Java).
	# - provided, indicates that the application has bound an instance of play.api.http.HttpErrorHandler through some
	# other mechanism.
	# If null, will attempt to load a class called ErrorHandler in the root package, otherwise if that's
	# not found, will default to play.api.http.DefaultHttpErrorHandler.
	errorHandler = null

[abhinandc3]

thanks this worked.
one question
DefaultHttpErrorHandler (scala method) is getting invoked
any idea why the java DefaultHttpErrorHandler (without the api) is not getting invoked
the app is built on java

[mkurz]

Not sure how that was implemented in 2.5.x, but it seems meanwhile implemention details changed:
Actually no matter if a scala or java project, the play.http.errorHandler config can either be a class extending play.http.HttpErrorHandler or play.api.http.HttpErrorHandler (that's also what the comments above says 😉). It does not matter which of those interface/trait you use. It also does not matter if you inject an subclass of play.http.HttpErrorHandler or of play.api.http.HttpErrorHandler somewhere in your code, play takes care of providing you the correct handler by converting it to a java or scala one with special adapter and delegate classes.
So by default play.api.http.DefaultHttpErrorHandler is set because like said Play can handle both, not matter if a java or scala project.
play.http.DefaultHttpErrorHandler still exists to make it easier for Java devs to extend it for customization purposes.
That means, if you want, you can just set play.http.errorHandler = play.http.DefaultHttpErrorHandler and everything should work like before and then you can attach the debugger to that java class if that is what you want, to keep it "pure java".
The default setting of using the scala (api) one does not really matter in the end since the they both behave exactly the same: You can compare the two implementations

• play.http.DefaultHttpErrorHandler
• play.api.http.DefaultHttpErrorHandler

In theory we (Play) could set play.http.errorHandler = play.http.DefaultHttpErrorHandler in the play-java reference.conf so for java projects that one will be used... (In theorie, because having the same config key play.http.errorHandler in two reference.conf files doesn't work since it's a gamble which one gets loaded first, so in real life we would need to use a reference-overrides.conf). But I don't think this is worth it.