Exception handler methods may receive original as well as cause

Issue: SPR-15701

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/RequestMappingHandlerAdapter.java

@@ -198,20 +198,25 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 						.onErrorResume(exceptionHandler)));
 	}
 
-	private Mono<HandlerResult> handleException(Throwable ex, HandlerMethod handlerMethod,
+	private Mono<HandlerResult> handleException(Throwable exception, HandlerMethod handlerMethod,
 			BindingContext bindingContext, ServerWebExchange exchange) {
 
 		Assert.state(this.methodResolver != null, "Not initialized");
 
-		InvocableHandlerMethod invocable = this.methodResolver.getExceptionHandlerMethod(ex, handlerMethod);
+		InvocableHandlerMethod invocable = this.methodResolver.getExceptionHandlerMethod(exception, handlerMethod);
 		if (invocable != null) {
 			try {
 				if (logger.isDebugEnabled()) {
 					logger.debug("Invoking @ExceptionHandler method: " + invocable.getMethod());
 				}
 				bindingContext.getModel().asMap().clear();
-				Throwable cause = ex.getCause() != null ? ex.getCause() : ex;
-				return invocable.invoke(exchange, bindingContext, cause, handlerMethod);
+				Throwable cause = exception.getCause();
+				if (cause != null) {
+					return invocable.invoke(exchange, bindingContext, exception, cause, handlerMethod);
+				}
+				else {
+					return invocable.invoke(exchange, bindingContext, exception, handlerMethod);
+				}
 			}
 			catch (Throwable invocationEx) {
 				if (logger.isWarnEnabled()) {
@@ -219,7 +224,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 				}
 			}
 		}
-		return Mono.error(ex);
+		return Mono.error(exception);
 	}
 
 }

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestMappingExceptionHandlingIntegrationTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.web.reactive.result.method.annotation;
 
+import java.io.IOException;
+
 import org.junit.Test;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
@@ -37,6 +39,7 @@ import static org.junit.Assert.*;
  * {@code @RequestMapping} integration tests with exception handling scenarios.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  */
 public class RequestMappingExceptionHandlingIntegrationTests extends AbstractRequestMappingIntegrationTests {
 
@@ -55,6 +58,18 @@ public class RequestMappingExceptionHandlingIntegrationTests extends AbstractReq
 		assertEquals(expected, performGet("/thrown-exception", new HttpHeaders(), String.class).getBody());
 	}
 
+	@Test
+	public void controllerThrowingExceptionWithCause() throws Exception {
+		String expected = "Recovered from error: State";
+		assertEquals(expected, performGet("/thrown-exception-with-cause", new HttpHeaders(), String.class).getBody());
+	}
+
+	@Test
+	public void controllerThrowingExceptionWithCauseToHandle() throws Exception {
+		String expected = "Recovered from error: IO";
+		assertEquals(expected, performGet("/thrown-exception-with-cause-to-handle", new HttpHeaders(), String.class).getBody());
+	}
+
 	@Test
 	public void controllerReturnsMonoError() throws Exception {
 		String expected = "Recovered from error: Argument";
@@ -79,11 +94,26 @@ public class RequestMappingExceptionHandlingIntegrationTests extends AbstractReq
 			throw new IllegalStateException("State");
 		}
 
+		@GetMapping("/thrown-exception-with-cause")
+		public Publisher<String> handleAndThrowExceptionWithCause() {
+			throw new IllegalStateException("State", new IOException("IO"));
+		}
+
+		@GetMapping("/thrown-exception-with-cause-to-handle")
+		public Publisher<String> handleAndThrowExceptionWithCauseToHandle() {
+			throw new RuntimeException("State", new IOException("IO"));
+		}
+
 		@GetMapping("/mono-error")
 		public Publisher<String> handleWithError() {
 			return Mono.error(new IllegalArgumentException("Argument"));
 		}
 
+		@ExceptionHandler
+		public Publisher<String> handleArgumentException(IOException ex) {
+			return Mono.just("Recovered from error: " + ex.getMessage());
+		}
+
 		@ExceptionHandler
 		public Publisher<String> handleArgumentException(IllegalArgumentException ex) {
 			return Mono.just("Recovered from error: " + ex.getMessage());