Restore ApplicationServletEnvironment in web deployments

Closes gh-48254

Author: snicoll

core/spring-boot/src/main/java/org/springframework/boot/web/servlet/support/SpringBootServletInitializer.java

@@ -43,6 +43,7 @@
 import org.springframework.boot.web.context.servlet.WebApplicationContextInitializer;
 import org.springframework.boot.web.servlet.ServletContextInitializer;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextException;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Configuration;
@@ -295,6 +296,17 @@ private WarDeploymentApplicationContextFactory(ServletContext servletContext) {
 			this.servletContext = servletContext;
 		}
 
+		@Override
+		public @Nullable Class<? extends ConfigurableEnvironment> getEnvironmentType(
+				@Nullable WebApplicationType webApplicationType) {
+			return (webApplicationType != WebApplicationType.SERVLET) ? null : ApplicationServletEnvironment.class;
+		}
+
+		@Override
+		public ConfigurableEnvironment createEnvironment(@Nullable WebApplicationType webApplicationType) {
+			return new ApplicationServletEnvironment();
+		}
+
 		@Override
 		public ConfigurableApplicationContext create(@Nullable WebApplicationType webApplicationType) {
 			return new AnnotationConfigServletWebApplicationContext() {
@@ -307,18 +319,13 @@ protected void onRefresh() {
 							.initialize(WarDeploymentApplicationContextFactory.this.servletContext);
 					}
 					catch (ServletException ex) {
-						throw new RuntimeException(ex);
+						throw new ApplicationContextException("Cannot initialize servlet context", ex);
 					}
 				}
 
 			};
 		}
 
-		@Override
-		public ConfigurableEnvironment createEnvironment(@Nullable WebApplicationType webApplicationType) {
-			return new ApplicationServletEnvironment();
-		}
-
 	}
 
 }

core/spring-boot/src/test/java/org/springframework/boot/web/servlet/support/SpringBootServletInitializerTests.java

@@ -47,6 +47,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.support.AbstractApplicationContext;
 import org.springframework.core.Ordered;
+import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.PropertySource;
 import org.springframework.mock.web.MockServletContext;
 import org.springframework.test.util.ReflectionTestUtils;
@@ -177,6 +178,29 @@ void executableWarThatUsesServletInitializerDoesNotHaveErrorPageFilterConfigured
 		}
 	}
 
+	@Test
+	void environmentIsConfiguredWithStandardServletEnvironment() {
+		ServletContext servletContext = mock(ServletContext.class);
+		given(servletContext.addFilter(any(), any(Filter.class))).willReturn(mock(Dynamic.class));
+		given(servletContext.getInitParameterNames())
+			.willReturn(Collections.enumeration(Collections.singletonList("servlet.init.test")));
+		given(servletContext.getInitParameter("servlet.init.test")).willReturn("from-servlet-context");
+		given(servletContext.getAttributeNames())
+			.willReturn(Collections.enumeration(Collections.singletonList("servlet.attribute.test")));
+		given(servletContext.getAttribute("servlet.attribute.test")).willReturn("also-from-servlet-context");
+		try (ConfigurableApplicationContext context = (ConfigurableApplicationContext) new RegularSpringBootServletInitializer()
+			.createRootApplicationContext(servletContext)) {
+			assertThat(context).isNotNull();
+			ConfigurableEnvironment environment = context.getEnvironment();
+			assertThat(environment).isInstanceOf(StandardServletEnvironment.class);
+			assertThat(environment.getClass().getName()).endsWith("ApplicationServletEnvironment");
+			assertThat(environment.getPropertySources()).map(PropertySource::getName)
+				.contains(StandardServletEnvironment.SERVLET_CONTEXT_PROPERTY_SOURCE_NAME,
+						StandardServletEnvironment.SERVLET_CONFIG_PROPERTY_SOURCE_NAME);
+			assertThat(environment.getProperty("servlet.init.test")).isEqualTo("from-servlet-context");
+		}
+	}
+
 	@Test
 	void servletContextPropertySourceIsAvailablePriorToRefresh() {
 		ServletContext servletContext = mock(ServletContext.class);
@@ -334,6 +358,15 @@ public SpringApplication build() {
 
 	}
 
+	static class RegularSpringBootServletInitializer extends SpringBootServletInitializer {
+
+		@Override
+		protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
+			return builder.sources(TestApp.class);
+		}
+
+	}
+
 	private static final class PropertySourceVerifyingApplicationListener
 			implements ApplicationListener<ApplicationEnvironmentPreparedEvent> {