Fix detection of WebApplicationType with context class

Closes gh-14589

Author: snicoll

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -43,6 +43,7 @@
 import org.springframework.boot.context.properties.bind.Bindable;
 import org.springframework.boot.context.properties.bind.Binder;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
+import org.springframework.boot.web.reactive.context.ReactiveWebApplicationContext;
 import org.springframework.boot.web.reactive.context.StandardReactiveWebEnvironment;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
@@ -1181,18 +1182,19 @@ public void setResourceLoader(ResourceLoader resourceLoader) {
 	public void setApplicationContextClass(
 			Class<? extends ConfigurableApplicationContext> applicationContextClass) {
 		this.applicationContextClass = applicationContextClass;
-		if (!isWebApplicationContext(applicationContextClass)) {
-			this.webApplicationType = WebApplicationType.NONE;
-		}
+		this.webApplicationType = deduceWebApplicationType(applicationContextClass);
 	}
 
-	private boolean isWebApplicationContext(Class<?> applicationContextClass) {
-		try {
-			return WebApplicationContext.class.isAssignableFrom(applicationContextClass);
+	private WebApplicationType deduceWebApplicationType(
+			Class<?> applicationContextClass) {
+		if (WebApplicationContext.class.isAssignableFrom(applicationContextClass)) {
+			return WebApplicationType.SERVLET;
 		}
-		catch (NoClassDefFoundError ex) {
-			return false;
+		if (ReactiveWebApplicationContext.class
+				.isAssignableFrom(applicationContextClass)) {
+			return WebApplicationType.REACTIVE;
 		}
+		return WebApplicationType.NONE;
 	}
 
 	/**

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -58,6 +58,7 @@
 import org.springframework.boot.testsupport.rule.OutputCapture;
 import org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory;
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
+import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebApplicationContext;
 import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext;
 import org.springframework.boot.web.reactive.context.ReactiveWebApplicationContext;
 import org.springframework.boot.web.reactive.context.StandardReactiveWebEnvironment;
@@ -96,6 +97,7 @@
 import org.springframework.util.StringUtils;
 import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
 import org.springframework.web.context.support.StandardServletEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -316,6 +318,32 @@ public void specificApplicationContextClass() {
 		assertThat(this.context).isInstanceOf(StaticApplicationContext.class);
 	}
 
+	@Test
+	public void specificWebApplicationContextClassDetectWebApplicationType() {
+		SpringApplication application = new SpringApplication(ExampleConfig.class);
+		application
+				.setApplicationContextClass(AnnotationConfigWebApplicationContext.class);
+		assertThat(application.getWebApplicationType())
+				.isEqualTo(WebApplicationType.SERVLET);
+	}
+
+	@Test
+	public void specificReactiveApplicationContextClassDetectReactiveApplicationType() {
+		SpringApplication application = new SpringApplication(ExampleConfig.class);
+		application.setApplicationContextClass(
+				AnnotationConfigReactiveWebApplicationContext.class);
+		assertThat(application.getWebApplicationType())
+				.isEqualTo(WebApplicationType.REACTIVE);
+	}
+
+	@Test
+	public void nonWebNorReactiveApplicationContextClassDetectNoneApplicationType() {
+		SpringApplication application = new SpringApplication(ExampleConfig.class);
+		application.setApplicationContextClass(StaticApplicationContext.class);
+		assertThat(application.getWebApplicationType())
+				.isEqualTo(WebApplicationType.NONE);
+	}
+
 	@Test
 	public void specificApplicationContextInitializer() {
 		SpringApplication application = new SpringApplication(ExampleConfig.class);