Spring 5 Reactive - WebExceptionHandler is not getting called - spring-boot

Question

I have tried all 3 solutions suggested in what is the right way to handle errors in spring-webflux, but WebExceptionHandler is not getting called. I am using Spring Boot 2.0.0.M7. Github repo here
#Configuration
class RoutesConfiguration {
#Autowired
private lateinit var testService: TestService
#Autowired
private lateinit var globalErrorHandler: GlobalErrorHandler
#Bean
fun routerFunction():
RouterFunction<ServerResponse> = router {
("/test").nest {
GET("/") {
ServerResponse.ok().body(testService.test())
}
}
}
}
#Component
class GlobalErrorHandler() : WebExceptionHandler {
companion object {
private val log = LoggerFactory.getLogger(GlobalErrorHandler::class.java)
}
override fun handle(exchange: ServerWebExchange?, ex: Throwable?): Mono<Void> {
log.info("inside handle")
/* Handle different exceptions here */
when(ex!!) {
is ClientException -> exchange!!.response.statusCode = HttpStatus.BAD_REQUEST
is Exception -> exchange!!.response.statusCode = HttpStatus.INTERNAL_SERVER_ERROR
}
return Mono.empty()
}
}
UPDATE:
When I change Spring Boot version to 2.0.0.M2, the WebExceptionHandler is getting called. Do I need to do something for 2.0.0.M7?
SOLUTION:
As per Brian's suggestion, it worked as
#Bean
#Order(-2)
fun globalErrorHandler() = GlobalErrorHandler()

Answer 1

You can provide your own WebExceptionHandler, but you have to order it relatively to others, otherwise they might handle the error before yours get a chance to try.
the DefaultErrorWebExceptionHandler provided by Spring Boot for error handling (see reference documentation) is ordered at -1
the ResponseStatusExceptionHandler provided by Spring Framework is ordered at 0
So you can add #Order(-2) on your error handling component, to order it before the existing ones.

Answer 2

An error response should have standard payload info. This can be done by extending AbstractErrorWebExceptionHandler
ErrorResponse: Data Class
data class ErrorResponse(
val timestamp: String,
val path: String,
val status: Int,
val error: String,
val message: String
)
ServerResponseBuilder: 2 different methods to build an error response
default: handle standard errors
webClient: handle webClient exceptions (WebClientResponseException), not for this case
class ServerResponseBuilder(
private val request: ServerRequest,
private val status: HttpStatus) {
fun default(): Mono<ServerResponse> =
ServerResponse
.status(status)
.body(BodyInserters.fromObject(ErrorResponse(
Date().format(),
request.path(),
status.value(),
status.name,
status.reasonPhrase)))
fun webClient(e: WebClientResponseException): Mono<ServerResponse> =
ServerResponse
.status(status)
.body(BodyInserters.fromObject(ErrorResponse(
Date().format(),
request.path(),
e.statusCode.value(),
e.message.toString(),
e.responseBodyAsString)))
}
GlobalErrorHandlerConfiguration: Error handler
#Configuration
#Order(-2)
class GlobalErrorHandlerConfiguration #Autowired constructor(
errorAttributes: ErrorAttributes,
resourceProperties: ResourceProperties,
applicationContext: ApplicationContext,
viewResolversProvider: ObjectProvider<List<ViewResolver>>,
serverCodecConfigurer: ServerCodecConfigurer) :
AbstractErrorWebExceptionHandler(
errorAttributes,
resourceProperties,
applicationContext
) {
init {
setViewResolvers(viewResolversProvider.getIfAvailable { emptyList() })
setMessageWriters(serverCodecConfigurer.writers)
setMessageReaders(serverCodecConfigurer.readers)
}
override fun getRoutingFunction(errorAttributes: ErrorAttributes?): RouterFunction<ServerResponse> =
RouterFunctions.route(RequestPredicates.all(), HandlerFunction<ServerResponse> { response(it, errorAttributes) })
private fun response(request: ServerRequest, errorAttributes: ErrorAttributes?): Mono<ServerResponse> =
ServerResponseBuilder(request, status(request, errorAttributes)).default()
private fun status(request: ServerRequest, errorAttributes: ErrorAttributes?) =
HttpStatus.valueOf(errorAttributesMap(request, errorAttributes)["status"] as Int)
private fun errorAttributesMap(request: ServerRequest, errorAttributes: ErrorAttributes?) =
errorAttributes!!.getErrorAttributes(request, false)
}