ControllerAdvice/ExceptionHandler do not apply to non reactive RouterFunction

[thiagolocatelli]

I have set up a small spring boot application to test a use case where the global exception handling feature through @ControllerAdvice and @ExceptionHandler does not work for any non reactive RouterFunction definitions.

While I am able to see the controller advice being activated when testing the controller mappings (ApplicationController.java below), when an exception is thrown from inside a handler class/method for a RouterFunction, AbstractHandlerExceptionResolver (most likely because the return type of the mapping is not ResponseEntity) fails to resolve the exception, thus returning There was an unexpected error (type=Internal Server Error, status=500).

The expectation was that by hitting the endpoint /fn/custom the resulting response would be HttpStatus BAD_REQUEST, instead of Internal Server Error

[hacked@dotenv ~/sb-geh] curl -v http://localhost:8080/controller/custom
* Host localhost:8080 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8080...
* Connected to localhost (::1) port 8080
> GET /controller/custom HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/8.6.0
> Accept: */*
>
< HTTP/1.1 400
< Content-Type: text/plain;charset=UTF-8
< Content-Length: 53
< Date: Thu, 06 Jun 2024 13:43:41 GMT
< Connection: close
<
* Closing connection
Custom Exception occurred: This is a custom exception

[hacked@dotenv ~/sb-geh] curl -v http://localhost:8080/fn/custom
* Host localhost:8080 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8080...
* Connected to localhost (::1) port 8080
> GET /fn/custom HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/8.6.0
> Accept: */*
>
< HTTP/1.1 500
< Content-Type: application/json
< Transfer-Encoding: chunked
< Date: Thu, 06 Jun 2024 13:43:48 GMT
< Connection: close
<
* Leftovers after chunking: 5 bytes
* Closing connection
{"timestamp":"2024-06-06T13:43:48.106+00:00","status":500,"error":"Internal Server Error","path":"/fn/custom"}

Steps to reproduce:

Using the latest version from start.spring.io

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.3.0</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

@ControllerAdvice

import com.example.globalexception.error.CustomException;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(CustomException.class)
    public ResponseEntity<String> handleCustomException(CustomException ex) {
        return new ResponseEntity<>("Custom Exception occurred: " + ex.getMessage(), HttpStatus.BAD_REQUEST);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<String> handleGenericException(Exception ex) {
        return new ResponseEntity<>("Internal Server Error: " + ex.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

RounterFunction configuration:

import com.example.globalexception.error.CustomException;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.function.RouterFunction;
import org.springframework.web.servlet.function.ServerRequest;
import org.springframework.web.servlet.function.ServerResponse;

import static org.springframework.web.servlet.function.RequestPredicates.*;
import static org.springframework.web.servlet.function.RouterFunctions.*;

@Configuration
public class RouterConfig {

    @Bean
    public RouterFunction<ServerResponse> custom() {
        return route(GET("fn/custom"), this::handleRequest);
    }

    @Bean
    public RouterFunction<ServerResponse> runtime() {
        return route(GET("fn/runtime"), this::handleRuntime);
    }

    public ServerResponse handleRequest(ServerRequest request) {
        throw new CustomException("Something went wrong");
    }

    public ServerResponse handleRuntime(ServerRequest request) {
        throw new RuntimeException("General error");
    }

}

Controller specification

import com.example.globalexception.error.CustomException;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/controller")
public class ApplicationController {

    @GetMapping("/custom")
    public String throwCustom() {
        throw new CustomException("This is a custom exception");
    }

    @GetMapping("/runtime")
    public String throwRuntime() {
        throw new CustomException("This is a runtime exception");
    }

}

Custom exception:

public class CustomException extends RuntimeException {

    public CustomException(final String message) {
        super(message);
    }
}

Console output for /fn/custom

2024-06-06T08:46:15.028-05:00 ERROR 9521 --- [global-exception] [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: com.example.globalexception.error.CustomException: Something went wrong] with root cause

com.example.globalexception.error.CustomException: Something went wrong
	at com.example.globalexception.config.RouterConfig.handleRequest(RouterConfig.java:29) ~[classes/:na]
	at org.springframework.web.servlet.function.support.HandlerFunctionAdapter.handle(HandlerFunctionAdapter.java:108) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.24.jar:6.0]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.8.jar:6.1.8]
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.24.jar:6.0]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.8.jar:6.1.8]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.8.jar:6.1.8]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.8.jar:6.1.8]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.8.jar:6.1.8]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.8.jar:6.1.8]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.8.jar:6.1.8]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:389) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.24.jar:10.1.24]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]

If this is not an issue, I am seeking for an alternative solution where we can apply a global exception handler for non reactive RouterFunction using the following classes:

import org.springframework.web.servlet.function.RouterFunction;
import org.springframework.web.servlet.function.ServerRequest;
import org.springframework.web.servlet.function.ServerResponse;

[wilkinsona]

You need to opt in to handling exceptions from handler functions. Please see spring-projects/spring-framework#32689 (comment) for details.