Relax ConfigurableWebEnvironment signatures

ConfigurableWebEnvironment was introduced in 3.2.0.M1 with SPR-9439 in
order to break a cyclic dependency. At the same time, certain signatures
such as AbstractRefreshableWebApplicationContext#getEnviroment and
GenericWebApplicationContext#getEnvironment were updated to take
advantage of covariant return types and return this newer, more narrow
type and providing cast-free calls to ConfigurableWebEnvironment methods
where necessary. Similar changes were made to HttpServletBean in
3.2.0.M2 with SPR-9763.

Narrowing #getEnvironment signatures in this fashion required enforcing
at the #setEnvironment level that any Environment instance provided
(explicitly or via the EnvironmentAware callback) must be an instance of
ConfigurableWebEnvironment. This is a reasonable assertion in typical
web application scenarios, but as SPR-10138 demonstrates, there are
valid use cases in which one may want or need to inject a non-web
ConfigurableEnvironment variant, e.g. during automated unit/integration
testing.

On review, it was never strictly necessary to narrow #getEnvironment
signatures, although doing so did provided convenience and type safety.
In order to maintain as flexible and backward-compatible an arrangement
as possible, this commit relaxes these #getEnvironment signatures back
to their original, pre-3.2 state. Namely, they now return
ConfigurableEnvironment as opposed to ConfigurableWebEnvironment, and in
accordance, all instanceof assertions have been removed or relaxed to
ensure that injected Environment instances are of type
ConfigurableEnvironment.

These changes have been verified against David Winterfeldt's Spring by
Example spring-rest-services project, as described at SPR-10138.

Issue: SPR-10138, SPR-9763, SPR-9439

spring-web/src/main/java/org/springframework/web/context/ConfigurableWebApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -71,11 +71,6 @@ public interface ConfigurableWebApplicationContext extends WebApplicationContext
 	 */
 	ServletConfig getServletConfig();
 
-	/**
-	 * Return the {@link ConfigurableWebEnvironment} used by this web application context.
-	 */
-	ConfigurableWebEnvironment getEnvironment();
-
 	/**
 	 * Set the namespace for this web application context,
 	 * to be used for building a default context config location.

spring-web/src/main/java/org/springframework/web/context/ContextLoader.java

@@ -38,6 +38,7 @@ import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.access.ContextSingletonBeanFactoryLocator;
 import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.support.PropertiesLoaderUtils;
 import org.springframework.util.Assert;
@@ -490,7 +491,10 @@ public class ContextLoader {
 			initializerInstances.add(BeanUtils.instantiateClass(initializerClass));
 		}
 
-		applicationContext.getEnvironment().initPropertySources(servletContext, null);
+		ConfigurableEnvironment env = applicationContext.getEnvironment();
+		if (env instanceof ConfigurableWebEnvironment) {
+			((ConfigurableWebEnvironment)env).initPropertySources(servletContext, null);
+		}
 
 		Collections.sort(initializerInstances, new AnnotationAwareOrderComparator());
 		for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : initializerInstances) {

spring-web/src/main/java/org/springframework/web/context/support/AbstractRefreshableWebApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -27,7 +27,6 @@ import org.springframework.core.io.support.ResourcePatternResolver;
 import org.springframework.ui.context.Theme;
 import org.springframework.ui.context.ThemeSource;
 import org.springframework.ui.context.support.UiApplicationContextUtils;
-import org.springframework.util.Assert;
 import org.springframework.web.context.ConfigurableWebApplicationContext;
 import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.ServletConfigAware;
@@ -157,15 +156,6 @@ public abstract class AbstractRefreshableWebApplicationContext extends AbstractR
 		return new StandardServletEnvironment();
 	}
 
-	@Override
-	public ConfigurableWebEnvironment getEnvironment() {
-		ConfigurableEnvironment env = super.getEnvironment();
-		Assert.isInstanceOf(ConfigurableWebEnvironment.class, env,
-				"ConfigurableWebApplicationContext environment must be of type " +
-				"ConfigurableWebEnvironment");
-		return (ConfigurableWebEnvironment) env;
-	}
-
 	/**
 	 * Register request/session scopes, a {@link ServletContextAwareProcessor}, etc.
 	 */
@@ -212,7 +202,11 @@ public abstract class AbstractRefreshableWebApplicationContext extends AbstractR
 	@Override
 	protected void initPropertySources() {
 		super.initPropertySources();
-		this.getEnvironment().initPropertySources(this.servletContext, this.servletConfig);
+		ConfigurableEnvironment env = this.getEnvironment();
+		if (env instanceof ConfigurableWebEnvironment) {
+			((ConfigurableWebEnvironment)env).initPropertySources(
+					this.servletContext, this.servletConfig);
+		}
 	}
 
 	public Theme getTheme(String themeName) {

spring-web/src/main/java/org/springframework/web/context/support/GenericWebApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -147,15 +147,6 @@ public class GenericWebApplicationContext extends GenericApplicationContext
 		return new StandardServletEnvironment();
 	}
 
-	@Override
-	public ConfigurableWebEnvironment getEnvironment() {
-		ConfigurableEnvironment env = super.getEnvironment();
-		Assert.isInstanceOf(ConfigurableWebEnvironment.class, env,
-				"ConfigurableWebApplicationContext environment must be of type " +
-				"ConfigurableWebEnvironment");
-		return (ConfigurableWebEnvironment) env;
-	}
-
 	/**
 	 * Register ServletContextAwareProcessor.
 	 * @see ServletContextAwareProcessor
@@ -202,7 +193,11 @@ public class GenericWebApplicationContext extends GenericApplicationContext
 	@Override
 	protected void initPropertySources() {
 		super.initPropertySources();
-		this.getEnvironment().initPropertySources(this.servletContext, null);
+		ConfigurableEnvironment env = this.getEnvironment();
+		if (env instanceof ConfigurableWebEnvironment) {
+			((ConfigurableWebEnvironment)env).initPropertySources(
+					this.servletContext, null);
+		}
 	}
 
 	public Theme getTheme(String themeName) {

spring-web/src/main/java/org/springframework/web/context/support/StaticWebApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -27,9 +27,7 @@ import org.springframework.core.io.support.ResourcePatternResolver;
 import org.springframework.ui.context.Theme;
 import org.springframework.ui.context.ThemeSource;
 import org.springframework.ui.context.support.UiApplicationContextUtils;
-import org.springframework.util.Assert;
 import org.springframework.web.context.ConfigurableWebApplicationContext;
-import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.ServletConfigAware;
 import org.springframework.web.context.ServletContextAware;
 
@@ -169,15 +167,6 @@ public class StaticWebApplicationContext extends StaticApplicationContext
 		return new StandardServletEnvironment();
 	}
 
-	@Override
-	public ConfigurableWebEnvironment getEnvironment() {
-		ConfigurableEnvironment env = super.getEnvironment();
-		Assert.isInstanceOf(ConfigurableWebEnvironment.class, env,
-				"ConfigurableWebApplication environment must be of type " +
-				"ConfigurableWebEnvironment");
-		return (ConfigurableWebEnvironment) env;
-	}
-
 	/**
 	 * Initialize the theme capability.
 	 */