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-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -73,6 +73,7 @@
 import org.springframework.core.PriorityOrdered;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
 import org.springframework.core.env.StandardEnvironment;
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.Resource;
@@ -224,7 +225,6 @@ public AbstractApplicationContext() {
 	public AbstractApplicationContext(ApplicationContext parent) {
 		this.parent = parent;
 		this.resourcePatternResolver = getResourcePatternResolver();
-		this.environment = this.createEnvironment();
 	}
 
 
@@ -276,7 +276,15 @@ public ApplicationContext getParent() {
 		return this.parent;
 	}
 
+	/**
+	 * {@inheritDoc}
+	 * <p>If {@code null}, a new environment will be initialized via
+	 * {@link #createEnvironment()}.
+	 */
 	public ConfigurableEnvironment getEnvironment() {
+		if (this.environment == null) {
+			this.environment = this.createEnvironment();
+		}
 		return this.environment;
 	}
 
@@ -387,9 +395,9 @@ protected ResourcePatternResolver getResourcePatternResolver() {
 	public void setParent(ApplicationContext parent) {
 		this.parent = parent;
 		if (parent != null) {
-			Object parentEnvironment =  parent.getEnvironment();
+			Environment parentEnvironment = parent.getEnvironment();
 			if (parentEnvironment instanceof ConfigurableEnvironment) {
-				this.environment.merge((ConfigurableEnvironment)parentEnvironment);
+				this.getEnvironment().merge((ConfigurableEnvironment)parentEnvironment);
 			}
 		}
 	}
@@ -505,7 +513,7 @@ protected void prepareRefresh() {
 
 		// Validate that all properties marked as required are resolvable
 		// see ConfigurablePropertyResolver#setRequiredProperties
-		this.environment.validateRequiredProperties();
+		this.getEnvironment().validateRequiredProperties();
 	}
 
 	/**

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

@@ -134,7 +134,8 @@ public String[] getConfigLocations() {
 	}
 
 	/**
-	 * Create and return a new {@link StandardServletEnvironment}.
+	 * Create and return a new {@link StandardServletEnvironment}. Subclasses may override
+	 * in order to configure the environment or specialize the environment type returned.
 	 */
 	@Override
 	protected ConfigurableEnvironment createEnvironment() {

spring-webmvc-portlet/src/main/java/org/springframework/web/portlet/FrameworkPortlet.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 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.
@@ -345,6 +345,7 @@ protected ApplicationContext createPortletApplicationContext(ApplicationContext
 			pac.setId(ConfigurablePortletApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + getPortletName());
 		}
 
+		pac.setEnvironment(this.getEnvironment());
 		pac.setParent(parent);
 		pac.setPortletContext(getPortletContext());
 		pac.setPortletConfig(getPortletConfig());

spring-webmvc-portlet/src/main/java/org/springframework/web/portlet/GenericPortletBean.java

@@ -34,13 +34,16 @@
 import org.springframework.beans.PropertyValue;
 import org.springframework.beans.PropertyValues;
 import org.springframework.context.EnvironmentAware;
+import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
+import org.springframework.core.env.EnvironmentCapable;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceEditor;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
-import org.springframework.web.portlet.context.StandardPortletEnvironment;
 import org.springframework.web.portlet.context.PortletContextResourceLoader;
+import org.springframework.web.portlet.context.StandardPortletEnvironment;
 
 /**
  * Simple extension of <code>javax.portlet.GenericPortlet</code> that treats
@@ -65,7 +68,8 @@
  * @see #processAction
  * @see FrameworkPortlet
  */
-public abstract class GenericPortletBean extends GenericPortlet implements EnvironmentAware {
+public abstract class GenericPortletBean extends GenericPortlet
+		implements EnvironmentCapable, EnvironmentAware {
 
 	/** Logger available to subclasses */
 	protected final Log logger = LogFactory.getLog(getClass());
@@ -76,7 +80,7 @@ public abstract class GenericPortletBean extends GenericPortlet implements Envir
 	 */
 	private final Set<String> requiredProperties = new HashSet<String>();
 
-	private Environment environment = new StandardPortletEnvironment();
+	private ConfigurableEnvironment environment;
 
 
 	/**
@@ -107,7 +111,7 @@ public final void init() throws PortletException {
 			PropertyValues pvs = new PortletConfigPropertyValues(getPortletConfig(), this.requiredProperties);
 			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
 			ResourceLoader resourceLoader = new PortletContextResourceLoader(getPortletContext());
-			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
+			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.getEnvironment()));
 			initBeanWrapper(bw);
 			bw.setPropertyValues(pvs, true);
 		}
@@ -167,17 +171,39 @@ protected void initPortletBean() throws PortletException {
 
 	/**
 	 * {@inheritDoc}
-	 * <p>Any environment set here overrides the {@link StandardPortletEnvironment}
-	 * provided by default.
+	 * @throws IllegalArgumentException if environment is not assignable to
+	 * {@code ConfigurableEnvironment}.
 	 */
 	public void setEnvironment(Environment environment) {
-		this.environment = environment;
+		Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
+		this.environment = (ConfigurableEnvironment)environment;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * <p>If {@code null}, a new environment will be initialized via
+	 * {@link #createEnvironment()}.
+	 */
+	public ConfigurableEnvironment getEnvironment() {
+		if (this.environment == null) {
+			this.environment = this.createEnvironment();
+		}
+		return this.environment;
+	}
+
+	/**
+	 * Create and return a new {@link StandardPortletEnvironment}. Subclasses may override
+	 * in order to configure the environment or specialize the environment type returned.
+	 */
+	protected ConfigurableEnvironment createEnvironment() {
+		return new StandardPortletEnvironment();
 	}
 
 
 	/**
 	 * PropertyValues implementation created from PortletConfig init parameters.
 	 */
+	@SuppressWarnings("serial")
 	private static class PortletConfigPropertyValues extends MutablePropertyValues {
 
 		/**

spring-webmvc-portlet/src/main/java/org/springframework/web/portlet/context/StandardPortletEnvironment.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 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.
@@ -75,7 +75,6 @@ public class StandardPortletEnvironment extends StandardEnvironment {
 	 * @see org.springframework.core.env.AbstractEnvironment#customizePropertySources
 	 * @see PortletConfigPropertySource
 	 * @see PortletContextPropertySource
-	 * @see AbstractRefreshablePortletApplicationContext#initPropertySources
 	 * @see PortletApplicationContextUtils#initPortletPropertySources
 	 */
 	@Override

spring-webmvc/src/main/java/org/springframework/web/servlet/FrameworkServlet.java

@@ -588,6 +588,7 @@ protected WebApplicationContext createWebApplicationContext(ApplicationContext p
 		ConfigurableWebApplicationContext wac =
 				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
 
+		wac.setEnvironment(this.getEnvironment());
 		wac.setParent(parent);
 		wac.setConfigLocation(getContextConfigLocation());
 

spring-webmvc/src/main/java/org/springframework/web/servlet/HttpServletBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 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.
@@ -35,11 +35,15 @@
 import org.springframework.beans.PropertyValue;
 import org.springframework.beans.PropertyValues;
 import org.springframework.context.EnvironmentAware;
+import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
+import org.springframework.core.env.EnvironmentCapable;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceEditor;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
+import org.springframework.web.context.ConfigurableWebEnvironment;
 import org.springframework.web.context.support.StandardServletEnvironment;
 import org.springframework.web.context.support.ServletContextResourceLoader;
 
@@ -76,7 +80,8 @@
  * @see #doPost
  */
 @SuppressWarnings("serial")
-public abstract class HttpServletBean extends HttpServlet implements EnvironmentAware {
+public abstract class HttpServletBean extends HttpServlet
+		implements EnvironmentCapable, EnvironmentAware {
 
 	/** Logger available to subclasses */
 	protected final Log logger = LogFactory.getLog(getClass());
@@ -87,7 +92,7 @@ public abstract class HttpServletBean extends HttpServlet implements Environment
 	 */
 	private final Set<String> requiredProperties = new HashSet<String>();
 
-	private Environment environment = new StandardServletEnvironment();
+	private ConfigurableWebEnvironment environment;
 
 
 	/**
@@ -120,7 +125,7 @@ public final void init() throws ServletException {
 			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
 			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
 			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
-			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
+			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.getEnvironment()));
 			initBeanWrapper(bw);
 			bw.setPropertyValues(pvs, true);
 		}
@@ -182,11 +187,32 @@ protected void initServletBean() throws ServletException {
 
 	/**
 	 * {@inheritDoc}
-	 * <p>Any environment set here overrides the {@link StandardServletEnvironment}
-	 * provided by default.
+	 * @throws IllegalArgumentException if environment is not assignable to
+	 * {@code ConfigurableWebEnvironment}.
 	 */
 	public void setEnvironment(Environment environment) {
-		this.environment = environment;
+		Assert.isInstanceOf(ConfigurableWebEnvironment.class, environment);
+		this.environment = (ConfigurableWebEnvironment)environment;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * <p>If {@code null}, a new environment will be initialized via
+	 * {@link #createEnvironment()}.
+	 */
+	public ConfigurableWebEnvironment getEnvironment() {
+		if (this.environment == null) {
+			this.environment = this.createEnvironment();
+		}
+		return this.environment;
+	}
+
+	/**
+	 * Create and return a new {@link StandardServletEnvironment}. Subclasses may override
+	 * in order to configure the environment or specialize the environment type returned.
+	 */
+	protected ConfigurableWebEnvironment createEnvironment() {
+		return new StandardServletEnvironment();
 	}
 
 

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 @@
 
 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.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.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 void testDispatcherServletContextRefresh() throws ServletException {
 		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 {