Refactor to lazy Environment creation where possible

This commit avoids eager creation of Environment instances, favoring
delegation of already existing Environment objects where possible. For
example, FrameworkServlet creates an ApplicationContext; both require
a StandardServletEnvironment instance, and prior to this change, two
instances were created where one would suffice - indeed these two
instances may reasonably be expected to be the same. Now, the
FrameworkServlet defers creation of its Environment, allowing users to
supply a custom instance via its #setEnvironment method (e.g. within a
WebApplicationInitializer); the FrameworkServlet then takes care to
delegate that instance to the ApplicationContext created
in #createWebApplicationContext.

This behavior produces more consistent behavior with regard to
delegation of the environment, saves unnecessary cycles by avoiding
needless instantiation and calls to methods like
StandardServletEnvironment#initPropertySources and leads to better
logging output, as the user sees only one Environment created and
initialized when working with the FrameworkServlet/DispatcherServlet.

This commit also mirrors these changes across the corresponding
Portlet* classes.

Issue: SPR-9763

spring-webmvc/src/test/java/org/springframework/web/servlet/DispatcherServletTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -18,6 +18,7 @@ package org.springframework.web.servlet;
 
 import java.io.IOException;
 import java.util.Locale;
+
 import javax.servlet.Servlet;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletContext;
@@ -33,14 +34,18 @@ import org.springframework.beans.PropertyValue;
 import org.springframework.beans.TestBean;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.support.DefaultMessageSourceResolvable;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.StandardEnvironment;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.mock.web.MockServletConfig;
 import org.springframework.mock.web.MockServletContext;
 import org.springframework.web.bind.EscapedErrors;
+import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.ServletConfigAwareBean;
 import org.springframework.web.context.ServletContextAwareBean;
 import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.context.support.StandardServletEnvironment;
 import org.springframework.web.context.support.StaticWebApplicationContext;
 import org.springframework.web.multipart.MaxUploadSizeExceededException;
 import org.springframework.web.multipart.MultipartHttpServletRequest;
@@ -55,6 +60,9 @@ import org.springframework.web.servlet.theme.AbstractThemeResolver;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;
 import org.springframework.web.util.WebUtils;
 
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
 /**
  * @author Rod Johnson
  * @author Juergen Hoeller
@@ -823,6 +831,30 @@ public class DispatcherServletTests extends TestCase {
 		servlet.destroy();
 	}
 
+	public void testEnvironmentOperations() {
+		DispatcherServlet servlet = new DispatcherServlet();
+		ConfigurableWebEnvironment defaultEnv = servlet.getEnvironment();
+		assertThat(defaultEnv, notNullValue());
+		ConfigurableEnvironment env1 = new StandardServletEnvironment();
+		servlet.setEnvironment(env1); // should succeed
+		assertThat(servlet.getEnvironment(), sameInstance(env1));
+		try {
+			servlet.setEnvironment(new StandardEnvironment());
+			fail("expected exception");
+		}
+		catch (IllegalArgumentException ex) {
+		}
+		class CustomServletEnvironment extends StandardServletEnvironment { }
+		@SuppressWarnings("serial")
+		DispatcherServlet custom = new DispatcherServlet() {
+			@Override
+			protected ConfigurableWebEnvironment createEnvironment() {
+				return new CustomServletEnvironment();
+			}
+		};
+		assertThat(custom.getEnvironment(), instanceOf(CustomServletEnvironment.class));
+	}
+
 
 	public static class ControllerFromParent implements Controller {