Handle exceptions in management context

Prior to this commit, details about an exception would get dropped when
the management context was separate from the application context and
an actuator endpoint threw a binding exception.

This commit adds some logic to capture the exception so the management
context error handlers can add the appropriate attributes to the error
response.

Fixes gh-21036

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/servlet/CompositeHandlerExceptionResolver.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.boot.actuate.autoconfigure.web.servlet;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -36,6 +37,7 @@ import org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolv
  * @author Andy Wilkinson
  * @author Stephane Nicoll
  * @author Phillip Webb
+ * @author Scott Frederick
  */
 class CompositeHandlerExceptionResolver implements HandlerExceptionResolver {
 
@@ -50,8 +52,15 @@ class CompositeHandlerExceptionResolver implements HandlerExceptionResolver {
 		if (this.resolvers == null) {
 			this.resolvers = extractResolvers();
 		}
-		return this.resolvers.stream().map((resolver) -> resolver.resolveException(request, response, handler, ex))
-				.filter(Objects::nonNull).findFirst().orElse(null);
+		Optional<ModelAndView> modelAndView = this.resolvers.stream()
+				.map((resolver) -> resolver.resolveException(request, response, handler, ex)).filter(Objects::nonNull)
+				.findFirst();
+		modelAndView.ifPresent((mav) -> {
+			if (mav.isEmpty()) {
+				request.setAttribute("javax.servlet.error.exception", ex);
+			}
+		});
+		return modelAndView.orElse(null);
 	}
 
 	private List<HandlerExceptionResolver> extractResolvers() {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/web/servlet/CompositeHandlerExceptionResolverTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,6 +38,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link CompositeHandlerExceptionResolver}.
  *
  * @author Madhura Bhave
+ * @author Scott Frederick
  */
 class CompositeHandlerExceptionResolverTests {
 
@@ -62,9 +63,11 @@ class CompositeHandlerExceptionResolverTests {
 		load(BaseConfiguration.class);
 		CompositeHandlerExceptionResolver resolver = (CompositeHandlerExceptionResolver) this.context
 				.getBean(DispatcherServlet.HANDLER_EXCEPTION_RESOLVER_BEAN_NAME);
-		ModelAndView resolved = resolver.resolveException(this.request, this.response, null,
-				new HttpRequestMethodNotSupportedException("POST"));
+		HttpRequestMethodNotSupportedException exception = new HttpRequestMethodNotSupportedException("POST");
+		ModelAndView resolved = resolver.resolveException(this.request, this.response, null, exception);
 		assertThat(resolved).isNotNull();
+		assertThat(resolved.isEmpty()).isTrue();
+		assertThat(this.request.getAttribute("javax.servlet.error.exception")).isSameAs(exception);
 	}
 
 	private void load(Class<?>... configs) {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/web/servlet/WebMvcEndpointChildContextConfigurationIntegrationTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,13 @@
 
 package org.springframework.boot.actuate.autoconfigure.web.servlet;
 
+import java.util.Collections;
+import java.util.Map;
+import java.util.function.Consumer;
+
+import javax.validation.Valid;
+import javax.validation.constraints.NotEmpty;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration;
@@ -23,15 +30,21 @@ import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAu
 import org.springframework.boot.actuate.autoconfigure.web.server.ManagementContextAutoConfiguration;
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
+import org.springframework.boot.actuate.endpoint.web.annotation.RestControllerEndpoint;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration;
+import org.springframework.boot.test.context.assertj.AssertableWebApplicationContext;
+import org.springframework.boot.test.context.runner.ContextConsumer;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer;
 import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;
 import org.springframework.http.MediaType;
-import org.springframework.stereotype.Component;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.reactive.function.client.ClientResponse;
 import org.springframework.web.reactive.function.client.WebClient;
 
@@ -41,29 +54,75 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Integration tests for {@link WebMvcEndpointChildContextConfiguration}.
  *
  * @author Phillip Webb
+ * @author Scott Frederick
  */
 class WebMvcEndpointChildContextConfigurationIntegrationTests {
 
+	final WebApplicationContextRunner contextRunner = new WebApplicationContextRunner(
+			AnnotationConfigServletWebServerApplicationContext::new)
+					.withConfiguration(AutoConfigurations.of(ServletWebServerFactoryAutoConfiguration.class,
+							ManagementContextAutoConfiguration.class, ServletManagementContextAutoConfiguration.class,
+							WebEndpointAutoConfiguration.class, EndpointAutoConfiguration.class,
+							DispatcherServletAutoConfiguration.class, ErrorMvcAutoConfiguration.class))
+					.withUserConfiguration(FailingEndpoint.class, FailingControllerEndpoint.class)
+					.withInitializer(new ServerPortInfoApplicationContextInitializer())
+					.withPropertyValues("server.port=0", "management.server.port=0",
+							"management.endpoints.web.exposure.include=*", "server.error.include-exception=true");
+
 	@Test // gh-17938
-	void errorPageAndErrorControllerAreUsed() {
-		new WebApplicationContextRunner(AnnotationConfigServletWebServerApplicationContext::new)
-				.withConfiguration(AutoConfigurations.of(ManagementContextAutoConfiguration.class,
-						ServletWebServerFactoryAutoConfiguration.class, ServletManagementContextAutoConfiguration.class,
-						WebEndpointAutoConfiguration.class, EndpointAutoConfiguration.class,
-						DispatcherServletAutoConfiguration.class, ErrorMvcAutoConfiguration.class))
-				.withUserConfiguration(FailingEndpoint.class)
-				.withInitializer(new ServerPortInfoApplicationContextInitializer()).withPropertyValues("server.port=0",
-						"management.server.port=0", "management.endpoints.web.exposure.include=*")
-				.run((context) -> {
-					String port = context.getEnvironment().getProperty("local.management.port");
-					WebClient client = WebClient.create("http://localhost:" + port);
-					ClientResponse response = client.get().uri("actuator/fail").accept(MediaType.APPLICATION_JSON)
-							.exchange().block();
-					assertThat(response.bodyToMono(String.class).block()).contains("message\":\"Epic Fail");
-				});
+	void errorEndpointIsUsedWithEndpoint() {
+		this.contextRunner.run(withWebTestClient((client) -> {
+			ClientResponse response = client.get().uri("actuator/fail").accept(MediaType.APPLICATION_JSON).exchange()
+					.block();
+			Map<String, ?> body = getResponseBody(response);
+			assertThat(body).hasEntrySatisfying("exception",
+					(value) -> assertThat(value).asString().contains("IllegalStateException"));
+			assertThat(body).hasEntrySatisfying("message",
+					(value) -> assertThat(value).asString().contains("Epic Fail"));
+		}));
+	}
+
+	@Test
+	void errorEndpointIsUsedWithRestControllerEndpoint() {
+		this.contextRunner.run(withWebTestClient((client) -> {
+			ClientResponse response = client.get().uri("actuator/failController").accept(MediaType.APPLICATION_JSON)
+					.exchange().block();
+			Map<String, ?> body = getResponseBody(response);
+			assertThat(body).hasEntrySatisfying("exception",
+					(value) -> assertThat(value).asString().contains("IllegalStateException"));
+			assertThat(body).hasEntrySatisfying("message",
+					(value) -> assertThat(value).asString().contains("Epic Fail"));
+		}));
+	}
+
+	@Test
+	void errorEndpointIsUsedWithRestControllerEndpointOnBindingError() {
+		this.contextRunner.run(withWebTestClient((client) -> {
+			ClientResponse response = client.post().uri("actuator/failController")
+					.bodyValue(Collections.singletonMap("content", "")).accept(MediaType.APPLICATION_JSON).exchange()
+					.block();
+			Map<String, ?> body = getResponseBody(response);
+			assertThat(body).hasEntrySatisfying("exception",
+					(value) -> assertThat(value).asString().contains("MethodArgumentNotValidException"));
+			assertThat(body).hasEntrySatisfying("message",
+					(value) -> assertThat(value).asString().contains("Validation failed"));
+			assertThat(body).hasEntrySatisfying("errors", (value) -> assertThat(value).asList().isNotEmpty());
+		}));
+	}
+
+	private ContextConsumer<AssertableWebApplicationContext> withWebTestClient(Consumer<WebClient> webClient) {
+		return (context) -> {
+			String port = context.getEnvironment().getProperty("local.management.port");
+			WebClient client = WebClient.create("http://localhost:" + port);
+			webClient.accept(client);
+		};
+	}
+
+	@SuppressWarnings("unchecked")
+	private Map<String, ?> getResponseBody(ClientResponse response) {
+		return (Map<String, ?>) response.bodyToMono(Map.class).block();
 	}
 
-	@Component
 	@Endpoint(id = "fail")
 	static class FailingEndpoint {
 
@@ -74,4 +133,35 @@ class WebMvcEndpointChildContextConfigurationIntegrationTests {
 
 	}
 
+	@RestControllerEndpoint(id = "failController")
+	static class FailingControllerEndpoint {
+
+		@GetMapping
+		String fail() {
+			throw new IllegalStateException("Epic Fail");
+		}
+
+		@PostMapping(produces = "application/json")
+		@ResponseBody
+		String bodyValidation(@Valid @RequestBody TestBody body) {
+			return body.getContent();
+		}
+
+	}
+
+	public static class TestBody {
+
+		@NotEmpty
+		private String content;
+
+		public String getContent() {
+			return this.content;
+		}
+
+		public void setContent(String content) {
+			this.content = content;
+		}
+
+	}
+
 }