Add a way to signal that an endpoint request is invalid

This commit adds InvalidEndpointRequestException as a technology
agnostic way to signal that an endpoint request is invalid. When such
exception is thrown, the web layer translates that to a 400.

Rather than overriding the reason, this commit makes sure to reuse the
error infrastructure.

Closes gh-10618

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/web/annotation/AbstractWebEndpointIntegrationTests.java

@@ -42,6 +42,7 @@ import org.springframework.context.annotation.Import;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.io.ByteArrayResource;
 import org.springframework.core.io.Resource;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
 import org.springframework.test.web.reactive.server.WebTestClient;
@@ -157,8 +158,13 @@ public abstract class AbstractWebEndpointIntegrationTests<T extends Configurable
 
 	@Test
 	public void readOperationWithMappingFailureProducesBadRequestResponse() {
-		load(QueryEndpointConfiguration.class, (client) -> client.get()
-				.uri("/query?two=two").exchange().expectStatus().isBadRequest());
+		load(QueryEndpointConfiguration.class, (client) -> {
+			WebTestClient.BodyContentSpec body = client.get()
+					.uri("/query?two=two").exchange().expectStatus().isBadRequest()
+					.expectBody();
+			validateErrorBody(body, HttpStatus.BAD_REQUEST, "/endpoints/query",
+					"Missing parameters: one");
+		});
 	}
 
 	@Test
@@ -275,8 +281,13 @@ public abstract class AbstractWebEndpointIntegrationTests<T extends Configurable
 
 	@Test
 	public void readOperationWithMissingRequiredParametersReturnsBadRequestResponse() {
-		load(RequiredParameterEndpointConfiguration.class, (client) -> client.get()
-				.uri("/requiredparameters").exchange().expectStatus().isBadRequest());
+		load(RequiredParameterEndpointConfiguration.class, (client) -> {
+			WebTestClient.BodyContentSpec body = client.get()
+					.uri("/requiredparameters").exchange().expectStatus().isBadRequest()
+					.expectBody();
+			validateErrorBody(body, HttpStatus.BAD_REQUEST,
+					"/endpoints/requiredparameters", "Missing parameters: foo");
+		});
 	}
 
 	@Test
@@ -321,6 +332,14 @@ public abstract class AbstractWebEndpointIntegrationTests<T extends Configurable
 
 	protected abstract int getPort(T context);
 
+	protected void validateErrorBody(WebTestClient.BodyContentSpec body,
+			HttpStatus status, String path, String message) {
+		body.jsonPath("status").isEqualTo(status.value())
+				.jsonPath("error").isEqualTo(status.getReasonPhrase())
+				.jsonPath("path").isEqualTo(path)
+				.jsonPath("message").isEqualTo(message);
+	}
+
 	private void load(Class<?> configuration,
 			BiConsumer<ApplicationContext, WebTestClient> consumer) {
 		load(configuration, "/endpoints", consumer);

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/web/jersey/JerseyWebEndpointIntegrationTests.java

@@ -37,6 +37,8 @@ import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebSe
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.env.Environment;
+import org.springframework.http.HttpStatus;
+import org.springframework.test.web.reactive.server.WebTestClient;
 
 /**
  * Integration tests for web endpoints exposed using Jersey.
@@ -64,6 +66,12 @@ public class JerseyWebEndpointIntegrationTests extends
 		return context.getWebServer().getPort();
 	}
 
+	@Override
+	protected void validateErrorBody(WebTestClient.BodyContentSpec body,
+			HttpStatus status, String path, String message) {
+		// Jersey doesn't support the general error page handling
+	}
+
 	@Configuration
 	static class JerseyConfiguration {
 

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/web/reactive/WebFluxEndpointIntegrationTests.java

@@ -23,6 +23,8 @@ import org.junit.Test;
 import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
 import org.springframework.boot.actuate.endpoint.web.annotation.AbstractWebEndpointIntegrationTests;
 import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpointDiscoverer;
+import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration;
 import org.springframework.boot.endpoint.web.EndpointMapping;
 import org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory;
 import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext;
@@ -95,6 +97,7 @@ public class WebFluxEndpointIntegrationTests
 
 	@Configuration
 	@EnableWebFlux
+	@ImportAutoConfiguration(ErrorWebFluxAutoConfiguration.class)
 	static class ReactiveConfiguration {
 
 		private int port;

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/web/servlet/MvcWebEndpointIntegrationTests.java

@@ -23,6 +23,13 @@ import org.junit.Test;
 import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
 import org.springframework.boot.actuate.endpoint.web.annotation.AbstractWebEndpointIntegrationTests;
 import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpointDiscoverer;
+import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
+import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration;
 import org.springframework.boot.endpoint.web.EndpointMapping;
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;
@@ -32,8 +39,6 @@ import org.springframework.core.env.Environment;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.web.cors.CorsConfiguration;
-import org.springframework.web.servlet.DispatcherServlet;
-import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -89,7 +94,10 @@ public class MvcWebEndpointIntegrationTests extends
 	}
 
 	@Configuration
-	@EnableWebMvc
+	@ImportAutoConfiguration({ JacksonAutoConfiguration.class,
+			HttpMessageConvertersAutoConfiguration.class,
+			ServletWebServerFactoryAutoConfiguration.class, WebMvcAutoConfiguration.class,
+			DispatcherServletAutoConfiguration.class, ErrorMvcAutoConfiguration.class })
 	static class WebMvcConfiguration {
 
 		@Bean
@@ -97,11 +105,6 @@ public class MvcWebEndpointIntegrationTests extends
 			return new TomcatServletWebServerFactory(0);
 		}
 
-		@Bean
-		public DispatcherServlet dispatcherServlet() {
-			return new DispatcherServlet();
-		}
-
 		@Bean
 		public WebMvcEndpointHandlerMapping webEndpointHandlerMapping(
 				Environment environment, WebEndpointDiscoverer endpointDiscoverer,