Merge pull request #30358 from terminux

* gh-30358:
  Polish "Add failure analyzer for missing web factory bean"
  Add failure analyzer for missing web factory bean

Closes gh-30358

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/context/MissingWebServerFactoryBeanException.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2012-2022 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.boot.web.context;
+
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.boot.WebApplicationType;
+import org.springframework.boot.web.server.WebServerFactory;
+
+/**
+ * Exception thrown when there is no {@link WebServerFactory} bean of the required type
+ * defined in a {@link WebServerApplicationContext}.
+ *
+ * @author Guirong Hu
+ * @author Andy Wilkinson
+ * @since 2.7.0
+ */
+public class MissingWebServerFactoryBeanException extends NoSuchBeanDefinitionException {
+
+	private final WebApplicationType webApplicationType;
+
+	/**
+	 * Create a new {@code MissingWebServerFactoryBeanException}.
+	 * @param webServerApplicationContextClass the class of the
+	 * WebServerApplicationContext that required the WebServerFactory
+	 * @param webServerFactoryClass the class of the WebServerFactory that was missing
+	 * @param webApplicationType the type of the web application
+	 */
+	public MissingWebServerFactoryBeanException(
+			Class<? extends WebServerApplicationContext> webServerApplicationContextClass,
+			Class<? extends WebServerFactory> webServerFactoryClass, WebApplicationType webApplicationType) {
+		super(webServerFactoryClass, String.format("Unable to start %s due to missing %s bean",
+				webServerApplicationContextClass.getSimpleName(), webServerFactoryClass.getSimpleName()));
+		this.webApplicationType = webApplicationType;
+	}
+
+	/**
+	 * Returns the type of web application for which a {@link WebServerFactory} bean was
+	 * missing.
+	 * @return the type of web application
+	 */
+	public WebApplicationType getWebApplicationType() {
+		return this.webApplicationType;
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/context/MissingWebServerFactoryBeanFailureAnalyzer.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2022 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.boot.web.context;
+
+import java.util.Locale;
+
+import org.springframework.boot.diagnostics.AbstractFailureAnalyzer;
+import org.springframework.boot.diagnostics.FailureAnalysis;
+import org.springframework.boot.diagnostics.FailureAnalyzer;
+import org.springframework.core.annotation.Order;
+
+/**
+ * A {@link FailureAnalyzer} that performs analysis of failures caused by an
+ * {@link MissingWebServerFactoryBeanException}.
+ *
+ * @author Guirong Hu
+ * @author Andy Wilkinson
+ */
+@Order(0)
+class MissingWebServerFactoryBeanFailureAnalyzer extends AbstractFailureAnalyzer<MissingWebServerFactoryBeanException> {
+
+	@Override
+	protected FailureAnalysis analyze(Throwable rootFailure, MissingWebServerFactoryBeanException cause) {
+		return new FailureAnalysis(
+				"Web application could not be started as there was no " + cause.getBeanType().getName()
+						+ " bean defined in the context.",
+				"Check your application's dependencies for a supported "
+						+ cause.getWebApplicationType().name().toLowerCase(Locale.ENGLISH) + " web server.\n"
+						+ "Check the configured web application type.",
+				cause);
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/reactive/context/ReactiveWebServerApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -18,9 +18,11 @@ package org.springframework.boot.web.reactive.context;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.availability.AvailabilityChangeEvent;
 import org.springframework.boot.availability.ReadinessState;
 import org.springframework.boot.web.context.ConfigurableWebServerApplicationContext;
+import org.springframework.boot.web.context.MissingWebServerFactoryBeanException;
 import org.springframework.boot.web.context.WebServerGracefulShutdownLifecycle;
 import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
 import org.springframework.boot.web.server.WebServer;
@@ -105,8 +107,8 @@ public class ReactiveWebServerApplicationContext extends GenericReactiveWebAppli
 		// Use bean names so that we don't consider the hierarchy
 		String[] beanNames = getBeanFactory().getBeanNamesForType(ReactiveWebServerFactory.class);
 		if (beanNames.length == 0) {
-			throw new ApplicationContextException(
+			throw new MissingWebServerFactoryBeanException(this.getClass(), ReactiveWebServerFactory.class,
-					"Unable to start ReactiveWebApplicationContext due to missing ReactiveWebServerFactory bean.");
+					WebApplicationType.REACTIVE);
 		}
 		if (beanNames.length > 1) {
 			throw new ApplicationContextException("Unable to start ReactiveWebApplicationContext due to multiple "

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/context/ServletWebServerApplicationContext.java

@@ -37,9 +37,11 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.config.Scope;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.availability.AvailabilityChangeEvent;
 import org.springframework.boot.availability.ReadinessState;
 import org.springframework.boot.web.context.ConfigurableWebServerApplicationContext;
+import org.springframework.boot.web.context.MissingWebServerFactoryBeanException;
 import org.springframework.boot.web.context.WebServerGracefulShutdownLifecycle;
 import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.servlet.FilterRegistrationBean;
@@ -207,8 +209,8 @@ public class ServletWebServerApplicationContext extends GenericWebApplicationCon
 		// Use bean names so that we don't consider the hierarchy
 		String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);
 		if (beanNames.length == 0) {
-			throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing "
+			throw new MissingWebServerFactoryBeanException(this.getClass(), ServletWebServerFactory.class,
-					+ "ServletWebServerFactory bean.");
+					WebApplicationType.SERVLET);
 		}
 		if (beanNames.length > 1) {
 			throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple "

spring-boot-project/spring-boot/src/main/resources/META-INF/spring.factories

@@ -74,7 +74,8 @@ org.springframework.boot.diagnostics.analyzer.InvalidConfigurationPropertyNameFa
 org.springframework.boot.diagnostics.analyzer.InvalidConfigurationPropertyValueFailureAnalyzer,\
 org.springframework.boot.diagnostics.analyzer.PatternParseFailureAnalyzer,\
 org.springframework.boot.liquibase.LiquibaseChangelogMissingFailureAnalyzer,\
-org.springframework.boot.web.embedded.tomcat.ConnectorStartFailureAnalyzer
+org.springframework.boot.web.context.MissingWebServerFactoryBeanFailureAnalyzer,\
+org.springframework.boot.web.embedded.tomcat.ConnectorStartFailureAnalyzer,\
 
 # Failure Analysis Reporters
 org.springframework.boot.diagnostics.FailureAnalysisReporter=\

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/context/MissingWebServerFactoryBeanFailureAnalyzerTests.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2012-2022 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.boot.web.context;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.diagnostics.FailureAnalysis;
+import org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext;
+import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
+import org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext;
+import org.springframework.boot.web.servlet.server.ServletWebServerFactory;
+import org.springframework.context.ApplicationContextException;
+import org.springframework.context.ConfigurableApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link MissingWebServerFactoryBeanFailureAnalyzer}.
+ *
+ * @author Guirong Hu
+ * @author Andy Wilkinson
+ */
+class MissingWebServerFactoryBeanFailureAnalyzerTests {
+
+	@Test
+	void missingServletWebServerFactoryBeanFailure() {
+		ApplicationContextException failure = createFailure(new ServletWebServerApplicationContext());
+		assertThat(failure).isNotNull();
+		FailureAnalysis analysis = new MissingWebServerFactoryBeanFailureAnalyzer().analyze(failure);
+		assertThat(analysis).isNotNull();
+		assertThat(analysis.getDescription()).isEqualTo("Web application could not be started as there was no "
+				+ ServletWebServerFactory.class.getName() + " bean defined in the context.");
+		assertThat(analysis.getAction()).isEqualTo(
+				"Check your application's dependencies for a supported servlet web server.\nCheck the configured web "
+						+ "application type.");
+	}
+
+	@Test
+	void missingReactiveWebServerFactoryBeanFailure() {
+		ApplicationContextException failure = createFailure(new ReactiveWebServerApplicationContext());
+		FailureAnalysis analysis = new MissingWebServerFactoryBeanFailureAnalyzer().analyze(failure);
+		assertThat(analysis).isNotNull();
+		assertThat(analysis.getDescription()).isEqualTo("Web application could not be started as there was no "
+				+ ReactiveWebServerFactory.class.getName() + " bean defined in the context.");
+		assertThat(analysis.getAction()).isEqualTo(
+				"Check your application's dependencies for a supported reactive web server.\nCheck the configured web "
+						+ "application type.");
+	}
+
+	private ApplicationContextException createFailure(ConfigurableApplicationContext context) {
+		try {
+			context.refresh();
+			context.close();
+			return null;
+		}
+		catch (ApplicationContextException ex) {
+			return ex;
+		}
+	}
+
+}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/context/ReactiveWebServerApplicationContextTests.java

@@ -61,7 +61,7 @@ class ReactiveWebServerApplicationContextTests {
 	void whenThereIsNoWebServerFactoryBeanThenContextRefreshWillFail() {
 		assertThatExceptionOfType(ApplicationContextException.class).isThrownBy(() -> this.context.refresh())
 				.withMessageContaining(
-						"Unable to start ReactiveWebApplicationContext due to missing ReactiveWebServerFactory bean");
+						"Unable to start ReactiveWebServerApplicationContext due to missing ReactiveWebServerFactory bean");
 	}
 
 	@Test

src/checkstyle/import-control.xml

@@ -93,6 +93,9 @@
 		</subpackage>
 		<subpackage name="server">
 			<disallow pkg="org.springframework.context" />
+			<subpackage name="context">
+				<allow pkg="org.springframework.context" />
+			</subpackage>
 		</subpackage>
 		<subpackage name="context">
 			<allow pkg="org.springframework.boot.web.server" />