Add initial support for error handling

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ProxyErrorController.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2023-2023 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.serverless.web;
+
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.servlet.ModelAndView;
+import org.springframework.web.servlet.view.json.MappingJackson2JsonView;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+@Controller
+@RequestMapping("/error")
+public class ProxyErrorController {
+
+	private final SimpleDateFormat df = new SimpleDateFormat("E, dd MMM yyyy HH:mm:ss z");
+
+	private final MappingJackson2JsonView view = new MappingJackson2JsonView();
+
+	@RequestMapping(produces = MediaType.TEXT_HTML_VALUE)
+	public ModelAndView errorHtml(HttpServletRequest request, HttpServletResponse response) {
+		HttpStatus status = getStatus(request);
+		Map<String, Object> model = new HashMap<>();
+		model.put("status", response.getStatus());
+		model.put("error", request.getAttribute(RequestDispatcher.ERROR_MESSAGE));
+		model.put("path", request.getAttribute(RequestDispatcher.ERROR_REQUEST_URI));
+		model.put("timestamp", df.format(new Date()));
+		response.setStatus(status.value());
+		ModelAndView modelAndView = resolveErrorView(request, response, status, model);
+		return (modelAndView != null) ? modelAndView : new ModelAndView("error", model);
+	}
+
+	protected ModelAndView resolveErrorView(HttpServletRequest request, HttpServletResponse response, HttpStatus status,
+			Map<String, Object> model) {
+		ModelAndView modelAndView = new ModelAndView("Whitelabel Error Page", model);
+		modelAndView.setStatus(status);
+		modelAndView.setView(this.view);
+		return modelAndView;
+	}
+
+	protected HttpStatus getStatus(HttpServletRequest request) {
+		Integer statusCode = (Integer) request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
+		if (statusCode == null) {
+			return HttpStatus.INTERNAL_SERVER_ERROR;
+		}
+		try {
+			return HttpStatus.valueOf(statusCode);
+		}
+		catch (Exception ex) {
+			return HttpStatus.INTERNAL_SERVER_ERROR;
+		}
+	}
+}

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ProxyHttpServletResponse.java

@@ -162,7 +162,7 @@ public class ProxyHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public boolean isCommitted() {
-		return true;
+		return false;
 	}
 
 	@Override

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ProxyMvc.java

@@ -27,6 +27,7 @@ import java.util.List;
 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.FilterConfig;
+import javax.servlet.RequestDispatcher;
 import javax.servlet.Servlet;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletContext;
@@ -36,10 +37,15 @@ import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.context.annotation.AnnotatedBeanDefinitionReader;
+import org.springframework.http.HttpStatus;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.context.ConfigurableWebApplicationContext;
 import org.springframework.web.context.support.GenericWebApplicationContext;
 import org.springframework.web.servlet.DispatcherServlet;
@@ -55,6 +61,8 @@ import org.springframework.web.servlet.DispatcherServlet;
  */
 public class ProxyMvc {
 
+	private static Log LOG = LogFactory.getLog(ProxyMvc.class);
+
 	static final String MVC_RESULT_ATTRIBUTE = ProxyMvc.class.getName().concat(".MVC_RESULT_ATTRIBUTE");
 
 	private final DispatcherServlet servlet;
@@ -71,6 +79,8 @@ public class ProxyMvc {
 		AnnotatedBeanDefinitionReader reader = new AnnotatedBeanDefinitionReader(applpicationContext);
 		reader.register(componentClasses);
 
+		reader.register(ProxyErrorController.class);
+
 		try {
 			DispatcherServlet servlet = new DispatcherServlet(applpicationContext);
 			servlet.init(new ProxyServletConfig(servletContext));
@@ -199,7 +209,40 @@ public class ProxyMvc {
 			public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
 					throws IOException, ServletException {
 
-				this.delegateServlet.service(request, response);
+				try {
+					this.delegateServlet.service(request, response);
+					if (((HttpServletResponse) response).getStatus() != HttpStatus.OK.value()) {
+						((ProxyHttpServletRequest) request).setAttribute(RequestDispatcher.ERROR_STATUS_CODE, ((HttpServletResponse) response).getStatus());
+						this.setErrorMessageAttribute((ProxyHttpServletRequest) request, (ProxyHttpServletResponse) response, null);
+						((ProxyHttpServletRequest) request).setAttribute(RequestDispatcher.ERROR_REQUEST_URI, ((ProxyHttpServletRequest) request).getRequestURI());
+
+						((ProxyHttpServletRequest) request).setRequestURI("/error");
+						this.delegateServlet.service(request, response);
+					}
+				}
+				catch (Exception e) {
+					((ProxyHttpServletRequest) request).setAttribute(RequestDispatcher.ERROR_STATUS_CODE, HttpStatus.INTERNAL_SERVER_ERROR);
+					this.setErrorMessageAttribute((ProxyHttpServletRequest) request, (ProxyHttpServletResponse) response, e);
+					((ProxyHttpServletRequest) request).setAttribute(RequestDispatcher.ERROR_EXCEPTION_TYPE, e);
+					((ProxyHttpServletRequest) request).setAttribute(RequestDispatcher.ERROR_REQUEST_URI, ((ProxyHttpServletRequest) request).getRequestURI());
+
+					LOG.error("Failed processing the request to: " + ((ProxyHttpServletRequest) request).getRequestURI(), e);
+					((ProxyHttpServletRequest) request).setRequestURI("/error");
+					this.delegateServlet.service(request, response);
+				}
+			}
+
+			private void setErrorMessageAttribute(ProxyHttpServletRequest request, ProxyHttpServletResponse response, Exception exception) {
+				if (exception != null && StringUtils.hasText(exception.getMessage())) {
+					request.setAttribute(RequestDispatcher.ERROR_MESSAGE, exception.getMessage());
+				}
+				else if (StringUtils.hasText(response.getErrorMessage())) {
+					request.setAttribute(RequestDispatcher.ERROR_MESSAGE, response.getErrorMessage());
+				}
+				else {
+					request.setAttribute(RequestDispatcher.ERROR_MESSAGE, HttpStatus.valueOf(response.getStatus()).getReasonPhrase());
+
+				}
 			}
 
 			@Override

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/test/java/org/springframework/cloud/function/serverless/web/RequestResponseTests.java

@@ -28,6 +28,7 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.cloud.function.test.app.Pet;
 import org.springframework.cloud.function.test.app.PetStoreSpringAppConfig;
+import org.springframework.http.HttpStatus;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -44,7 +45,7 @@ public class RequestResponseTests {
 
 	@BeforeEach
 	public void before() {
-		this.mvc = ProxyMvc.INSTANCE(PetStoreSpringAppConfig.class);
+		this.mvc = ProxyMvc.INSTANCE(PetStoreSpringAppConfig.class, ProxyErrorController.class);
 	}
 
 	@AfterEach
@@ -87,6 +88,23 @@ public class RequestResponseTests {
 		assertThat(pet.getName()).isNotEmpty();
 	}
 
+	@Test
+	public void errorThrownFromMethod() throws Exception {
+		HttpServletRequest request = new ProxyHttpServletRequest(null, "GET", "/pets/2");
+		ProxyHttpServletResponse response = new ProxyHttpServletResponse();
+		mvc.service(request, response);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+		assertThat(response.getErrorMessage()).isEqualTo("No such Dog");
+	}
+
+	@Test
+	public void errorUnexpectedWhitelabel() throws Exception {
+		HttpServletRequest request = new ProxyHttpServletRequest(null, "GET", "/pets/2/3/4");
+		ProxyHttpServletResponse response = new ProxyHttpServletResponse();
+		mvc.service(request, response);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+	}
+
 	@Test
 	public void validatePostWithBody() throws Exception {
 		ProxyHttpServletRequest request = new ProxyHttpServletRequest(null, "POST", "/pets/");

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/test/java/org/springframework/cloud/function/test/app/PetsController.java

@@ -20,10 +20,13 @@ import java.security.Principal;
 import java.util.Optional;
 import java.util.UUID;
 
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 
@@ -63,8 +66,10 @@ public class PetsController {
 	}
 
 	@RequestMapping(path = "/pets/{petId}", method = RequestMethod.GET)
-	public Pet listPets() {
+	public Pet listPets(@PathVariable String petId) {
-		System.out.println("=====> Getting pet by id");
+		if (petId.equals("2")) {
+			throw new DogNotFoundException();
+		}
 		Pet newPet = new Pet();
 		newPet.setId(UUID.randomUUID().toString());
 		newPet.setBreed(PetData.getRandomBreed());
@@ -72,4 +77,9 @@ public class PetsController {
 		newPet.setName(PetData.getRandomName());
 		return newPet;
 	}
+
+	@ResponseStatus(value = HttpStatus.NOT_FOUND, reason = "No such Dog") // 404
+	public class DogNotFoundException extends RuntimeException {
+		// ...
+	}
 }