Fix package tangle between SpringApplication and Environment types

Update `SpringApplication` so that it no longer directly decides the
type of `Environment` that should be created.

Closes gh-32825

Author: philwebb

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

@@ -20,8 +20,8 @@
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.context.ConfigurableApplicationContext;
-import org.springframework.context.annotation.AnnotationConfigApplicationContext;
-import org.springframework.core.io.support.SpringFactoriesLoader;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
 
 /**
  * Strategy interface for creating the {@link ConfigurableApplicationContext} used by a
@@ -40,22 +40,32 @@ public interface ApplicationContextFactory {
 	 * A default {@link ApplicationContextFactory} implementation that will create an
 	 * appropriate context for the {@link WebApplicationType}.
 	 */
-	ApplicationContextFactory DEFAULT = (webApplicationType) -> {
-		try {
-			for (ApplicationContextFactory candidate : SpringFactoriesLoader
-					.loadFactories(ApplicationContextFactory.class, ApplicationContextFactory.class.getClassLoader())) {
-				ConfigurableApplicationContext context = candidate.create(webApplicationType);
-				if (context != null) {
-					return context;
-				}
-			}
-			return new AnnotationConfigApplicationContext();
-		}
-		catch (Exception ex) {
-			throw new IllegalStateException("Unable create a default ApplicationContext instance, "
-					+ "you may need a custom ApplicationContextFactory", ex);
-		}
-	};
+	ApplicationContextFactory DEFAULT = new DefaultApplicationContextFactory();
+
+	/**
+	 * Return the {@link Environment} type expected to be set on the
+	 * {@link #create(WebApplicationType) created} application context. The result of this
+	 * method can be used to convert an existing environment instance to the correct type.
+	 * @param webApplicationType the web application type
+	 * @return the expected application context type or {@code null} to use the default
+	 * @since 2.6.14
+	 */
+	default Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicationType webApplicationType) {
+		return null;
+	}
+
+	/**
+	 * Create a new {@link Environment} to be set on the
+	 * {@link #create(WebApplicationType) created} application context. The result of this
+	 * method must match the type returned by
+	 * {@link #getEnvironmentType(WebApplicationType)}.
+	 * @param webApplicationType the web application type
+	 * @return an environment instance or {@code null} to use the default
+	 * @since 2.6.14
+	 */
+	default ConfigurableEnvironment createEnvironment(WebApplicationType webApplicationType) {
+		return null;
+	}
 
 	/**
 	 * Creates the {@link ConfigurableApplicationContext application context} for a

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

@@ -0,0 +1,69 @@
+/*
+ * 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;
+
+import java.util.function.BiFunction;
+import java.util.function.Supplier;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.io.support.SpringFactoriesLoader;
+
+/**
+ * Default {@link ApplicationContextFactory} implementation that will create an
+ * appropriate context for the {@link WebApplicationType}.
+ *
+ * @author Phillip Webb
+ */
+class DefaultApplicationContextFactory implements ApplicationContextFactory {
+
+	@Override
+	public Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicationType webApplicationType) {
+		return getFromSpringFactories(webApplicationType, ApplicationContextFactory::getEnvironmentType, null);
+	}
+
+	@Override
+	public ConfigurableEnvironment createEnvironment(WebApplicationType webApplicationType) {
+		return getFromSpringFactories(webApplicationType, ApplicationContextFactory::createEnvironment, null);
+	}
+
+	@Override
+	public ConfigurableApplicationContext create(WebApplicationType webApplicationType) {
+		try {
+			return getFromSpringFactories(webApplicationType, ApplicationContextFactory::create,
+					AnnotationConfigApplicationContext::new);
+		}
+		catch (Exception ex) {
+			throw new IllegalStateException("Unable create a default ApplicationContext instance, "
+					+ "you may need a custom ApplicationContextFactory", ex);
+		}
+	}
+
+	private <T> T getFromSpringFactories(WebApplicationType webApplicationType,
+			BiFunction<ApplicationContextFactory, WebApplicationType, T> action, Supplier<T> defaultResult) {
+		for (ApplicationContextFactory candidate : SpringFactoriesLoader.loadFactories(ApplicationContextFactory.class,
+				getClass().getClassLoader())) {
+			T result = action.apply(candidate, webApplicationType);
+			if (result != null) {
+				return result;
+			}
+		}
+		return (defaultResult != null) ? defaultResult.get() : null;
+	}
+
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.boot;
 
+import java.lang.reflect.Constructor;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
@@ -26,6 +27,7 @@
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.StandardEnvironment;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.web.context.support.StandardServletEnvironment;
 
 /**
@@ -87,10 +89,12 @@ private StandardEnvironment convertEnvironment(ConfigurableEnvironment environme
 
 	private StandardEnvironment createEnvironment(Class<? extends StandardEnvironment> type) {
 		try {
-			return type.getDeclaredConstructor().newInstance();
+			Constructor<? extends StandardEnvironment> constructor = type.getDeclaredConstructor();
+			ReflectionUtils.makeAccessible(constructor);
+			return constructor.newInstance();
 		}
 		catch (Exception ex) {
-			return new StandardEnvironment();
+			return new ApplicationEnvironment();
 		}
 	}
 

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

@@ -366,15 +366,18 @@ public StandardEnvironment convertEnvironment(ConfigurableEnvironment environmen
 				deduceEnvironmentClass());
 	}
 
+	@SuppressWarnings("unchecked")
 	private Class<? extends StandardEnvironment> deduceEnvironmentClass() {
-		switch (this.webApplicationType) {
-			case SERVLET:
-				return ApplicationServletEnvironment.class;
-			case REACTIVE:
-				return ApplicationReactiveWebEnvironment.class;
-			default:
-				return ApplicationEnvironment.class;
+		Class<? extends ConfigurableEnvironment> environmentType = this.applicationContextFactory
+				.getEnvironmentType(this.webApplicationType);
+		if (environmentType == null && this.applicationContextFactory != ApplicationContextFactory.DEFAULT) {
+			environmentType = ApplicationContextFactory.DEFAULT.getEnvironmentType(this.webApplicationType);
+		}
+		if (environmentType == null) {
+			return ApplicationEnvironment.class;
 		}
+		Assert.isAssignable(StandardEnvironment.class, environmentType);
+		return (Class<? extends StandardEnvironment>) environmentType;
 	}
 
 	private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
@@ -468,14 +471,11 @@ private ConfigurableEnvironment getOrCreateEnvironment() {
 		if (this.environment != null) {
 			return this.environment;
 		}
-		switch (this.webApplicationType) {
-			case SERVLET:
-				return new ApplicationServletEnvironment();
-			case REACTIVE:
-				return new ApplicationReactiveWebEnvironment();
-			default:
-				return new ApplicationEnvironment();
+		ConfigurableEnvironment environment = this.applicationContextFactory.createEnvironment(this.webApplicationType);
+		if (environment == null && this.applicationContextFactory != ApplicationContextFactory.DEFAULT) {
+			environment = ApplicationContextFactory.DEFAULT.createEnvironment(this.webApplicationType);
 		}
+		return (environment != null) ? environment : new ApplicationEnvironment();
 	}
 
 	/**

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

@@ -218,6 +218,16 @@ protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactor
 	 */
 	static class Factory implements ApplicationContextFactory {
 
+		@Override
+		public Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicationType webApplicationType) {
+			return (webApplicationType != WebApplicationType.REACTIVE) ? null : ApplicationReactiveWebEnvironment.class;
+		}
+
+		@Override
+		public ConfigurableEnvironment createEnvironment(WebApplicationType webApplicationType) {
+			return (webApplicationType != WebApplicationType.REACTIVE) ? null : new ApplicationReactiveWebEnvironment();
+		}
+
 		@Override
 		public ConfigurableApplicationContext create(WebApplicationType webApplicationType) {
 			return (webApplicationType != WebApplicationType.REACTIVE) ? null

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/ApplicationReactiveWebEnvironment.java renamed to spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/reactive/context/ApplicationReactiveWebEnvironment.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.
@@ -14,10 +14,10 @@
  * limitations under the License.
  */
 
-package org.springframework.boot;
+package org.springframework.boot.web.reactive.context;
 
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
-import org.springframework.boot.web.reactive.context.StandardReactiveWebEnvironment;
 import org.springframework.core.env.ConfigurablePropertyResolver;
 import org.springframework.core.env.MutablePropertySources;
 

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

@@ -215,6 +215,16 @@ protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactor
 	 */
 	static class Factory implements ApplicationContextFactory {
 
+		@Override
+		public Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicationType webApplicationType) {
+			return (webApplicationType != WebApplicationType.SERVLET) ? null : ApplicationServletEnvironment.class;
+		}
+
+		@Override
+		public ConfigurableEnvironment createEnvironment(WebApplicationType webApplicationType) {
+			return (webApplicationType != WebApplicationType.SERVLET) ? null : new ApplicationServletEnvironment();
+		}
+
 		@Override
 		public ConfigurableApplicationContext create(WebApplicationType webApplicationType) {
 			return (webApplicationType != WebApplicationType.SERVLET) ? null

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/ApplicationServletEnvironment.java renamed to spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/context/ApplicationServletEnvironment.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.
@@ -14,8 +14,9 @@
  * limitations under the License.
  */
 
-package org.springframework.boot;
+package org.springframework.boot.web.servlet.context;
 
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
 import org.springframework.core.env.ConfigurablePropertyResolver;
 import org.springframework.core.env.MutablePropertySources;

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

@@ -74,6 +74,7 @@
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext;
 import org.springframework.boot.web.reactive.context.ReactiveWebApplicationContext;
+import org.springframework.boot.web.reactive.context.StandardReactiveWebEnvironment;
 import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -472,15 +473,17 @@ void environmentForWeb() {
 		SpringApplication application = new SpringApplication(ExampleWebConfig.class);
 		application.setWebApplicationType(WebApplicationType.SERVLET);
 		this.context = application.run();
-		assertThat(this.context.getEnvironment()).isInstanceOf(ApplicationServletEnvironment.class);
+		assertThat(this.context.getEnvironment()).isInstanceOf(StandardServletEnvironment.class);
+		assertThat(this.context.getEnvironment().getClass().getName()).endsWith("ApplicationServletEnvironment");
 	}
 
 	@Test
 	void environmentForReactiveWeb() {
 		SpringApplication application = new SpringApplication(ExampleReactiveWebConfig.class);
 		application.setWebApplicationType(WebApplicationType.REACTIVE);
 		this.context = application.run();
-		assertThat(this.context.getEnvironment()).isInstanceOf(ApplicationReactiveWebEnvironment.class);
+		assertThat(this.context.getEnvironment()).isInstanceOf(StandardReactiveWebEnvironment.class);
+		assertThat(this.context.getEnvironment().getClass().getName()).endsWith("ApplicationReactiveWebEnvironment");
 	}
 
 	@Test
@@ -1055,7 +1058,7 @@ void getApplicationArgumentsBean() {
 	void webApplicationSwitchedOffInListener() {
 		TestSpringApplication application = new TestSpringApplication(ExampleConfig.class);
 		application.addListeners((ApplicationListener<ApplicationEnvironmentPreparedEvent>) (event) -> {
-			assertThat(event.getEnvironment()).isInstanceOf(ApplicationServletEnvironment.class);
+			assertThat(event.getEnvironment().getClass().getName()).endsWith("ApplicationServletEnvironment");
 			TestPropertySourceUtils.addInlinedPropertiesToEnvironment(event.getEnvironment(), "foo=bar");
 			event.getSpringApplication().setWebApplicationType(WebApplicationType.NONE);
 		});
@@ -1081,23 +1084,26 @@ void webApplicationConfiguredViaAPropertyHasTheCorrectTypeOfContextAndEnvironmen
 		ConfigurableApplicationContext context = new SpringApplication(ExampleWebConfig.class)
 				.run("--spring.main.web-application-type=servlet");
 		assertThat(context).isInstanceOf(WebApplicationContext.class);
-		assertThat(context.getEnvironment()).isInstanceOf(ApplicationServletEnvironment.class);
+		assertThat(context.getEnvironment()).isInstanceOf(StandardServletEnvironment.class);
+		assertThat(context.getEnvironment().getClass().getName()).endsWith("ApplicationServletEnvironment");
 	}
 
 	@Test
 	void reactiveApplicationConfiguredViaAPropertyHasTheCorrectTypeOfContextAndEnvironment() {
 		ConfigurableApplicationContext context = new SpringApplication(ExampleReactiveWebConfig.class)
 				.run("--spring.main.web-application-type=reactive");
 		assertThat(context).isInstanceOf(ReactiveWebApplicationContext.class);
-		assertThat(context.getEnvironment()).isInstanceOf(ApplicationReactiveWebEnvironment.class);
+		assertThat(context.getEnvironment()).isInstanceOf(StandardReactiveWebEnvironment.class);
+		assertThat(context.getEnvironment().getClass().getName()).endsWith("ApplicationReactiveWebEnvironment");
 	}
 
 	@Test
 	void environmentIsConvertedIfTypeDoesNotMatch() {
 		ConfigurableApplicationContext context = new SpringApplication(ExampleReactiveWebConfig.class)
 				.run("--spring.profiles.active=withwebapplicationtype");
 		assertThat(context).isInstanceOf(ReactiveWebApplicationContext.class);
-		assertThat(context.getEnvironment()).isInstanceOf(ApplicationReactiveWebEnvironment.class);
+		assertThat(context.getEnvironment()).isInstanceOf(StandardReactiveWebEnvironment.class);
+		assertThat(context.getEnvironment().getClass().getName()).endsWith("ApplicationReactiveWebEnvironment");
 	}
 
 	@Test

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/ApplicationReactiveWebEnvironmentTests.java renamed to spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/context/ApplicationReactiveWebEnvironmentTests.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.
@@ -14,8 +14,9 @@
  * limitations under the License.
  */
 
-package org.springframework.boot;
+package org.springframework.boot.web.reactive.context;
 
+import org.springframework.boot.AbstractApplicationEnvironmentTests;
 import org.springframework.core.env.StandardEnvironment;
 
 /**