Allow servlet context parmeters to be configured via declaratively

Previously, configuration of a ServletContext init parameter required
the use of a ServletContextInitializer bean. This commmit adds
support for declarative configuration via the environment using
server.context_parameters.<name>=<value>.

Closes gh-1791

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -19,6 +19,8 @@ package org.springframework.boot.autoconfigure.web;
 import java.io.File;
 import java.net.InetAddress;
 import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
 
 import javax.validation.constraints.NotNull;
 
@@ -33,6 +35,7 @@ import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletCont
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizerBeanPostProcessor;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
+import org.springframework.boot.context.embedded.InitParameterConfiguringServletContextInitializer;
 import org.springframework.boot.context.embedded.Ssl;
 import org.springframework.boot.context.embedded.tomcat.TomcatConnectorCustomizer;
 import org.springframework.boot.context.embedded.tomcat.TomcatContextCustomizer;
@@ -69,6 +72,8 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 
 	private final Tomcat tomcat = new Tomcat();
 
+	private final Map<String, String> contextParameters = new HashMap<String, String>();
+
 	public Tomcat getTomcat() {
 		return this.tomcat;
 	}
@@ -145,6 +150,10 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 		this.ssl = ssl;
 	}
 
+	public Map<String, String> getContextParameters() {
+		return this.contextParameters;
+	}
+
 	public void setLoader(String value) {
 		// no op to support Tomcat running as a traditional container (not embedded)
 	}
@@ -170,6 +179,9 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 			getTomcat()
 					.customizeTomcat((TomcatEmbeddedServletContainerFactory) container);
 		}
+
+		container.addInitializers(new InitParameterConfiguringServletContextInitializer(
+				getContextParameters()));
 	}
 
 	public String[] getPathsArray(Collection<String> paths) {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/EmbeddedServletContainerAutoConfigurationTests.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.web;
 
 import javax.servlet.Servlet;
+import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
@@ -30,6 +31,7 @@ import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomi
 import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
 import org.springframework.boot.context.embedded.MockEmbeddedServletContainerFactory;
 import org.springframework.boot.context.embedded.ServletRegistrationBean;
+import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -112,6 +114,19 @@ public class EmbeddedServletContainerAutoConfigurationTests {
 		assertEquals(9000, getContainerFactory().getPort());
 	}
 
+	@Test
+	public void initParametersAreConfiguredOnTheServletContext() {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"server.context_parameters.a:alpha", "server.context_parameters.b:bravo");
+		this.context.register(BaseConfiguration.class);
+		this.context.refresh();
+
+		ServletContext servletContext = this.context.getServletContext();
+		assertEquals("alpha", servletContext.getInitParameter("a"));
+		assertEquals("bravo", servletContext.getInitParameter("b"));
+	}
+
 	private void verifyContext() {
 		MockEmbeddedServletContainerFactory containerFactory = getContainerFactory();
 		Servlet servlet = this.context.getBean(

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -54,6 +54,7 @@ content into your application; rather pick only the properties that you need.
 	server.port=8080
 	server.address= # bind to a specific NIC
 	server.session-timeout= # session timeout in seconds
+	server.context-parameters.*= # Servlet context init parameters, e.g. server.context-parameters.a=alpha
 	server.context-path= # the context path, defaults to '/'
 	server.servlet-path= # the servlet path, defaults to '/'
 	server.ssl.client-auth= # want or need

spring-boot/src/main/java/org/springframework/boot/context/embedded/InitParameterConfiguringServletContextInitializer.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2014 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
+ *
+ *      http://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.context.embedded;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletException;
+
+/**
+ * A {@code ServletContextInitializer} that configures init parameters on the
+ * {@code ServletContext}.
+ *
+ * @author Andy Wilkinson
+ * @since 1.2.0
+ * @see ServletContext#setInitParameter(String, String)
+ */
+public class InitParameterConfiguringServletContextInitializer implements
+		ServletContextInitializer {
+
+	private final Map<String, String> parameters;
+
+	public InitParameterConfiguringServletContextInitializer(
+			Map<String, String> parameters) {
+		this.parameters = parameters;
+	}
+
+	@Override
+	public void onStartup(ServletContext servletContext) throws ServletException {
+		for (Entry<String, String> entry : this.parameters.entrySet()) {
+			servletContext.setInitParameter(entry.getKey(), entry.getValue());
+		}
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/embedded/MockEmbeddedServletContainerFactory.java

@@ -17,8 +17,11 @@
 package org.springframework.boot.context.embedded;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Enumeration;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.NoSuchElementException;
 
 import javax.servlet.Filter;
@@ -42,6 +45,7 @@ import static org.mockito.Mockito.spy;
  * Mock {@link EmbeddedServletContainerFactory}.
  *
  * @author Phillip Webb
+ * @author Andy Wilkinson
  */
 public class MockEmbeddedServletContainerFactory extends
 		AbstractEmbeddedServletContainerFactory {
@@ -51,7 +55,8 @@ public class MockEmbeddedServletContainerFactory extends
 	@Override
 	public EmbeddedServletContainer getEmbeddedServletContainer(
 			ServletContextInitializer... initializers) {
-		this.container = spy(new MockEmbeddedServletContainer(initializers, getPort()));
+		this.container = spy(new MockEmbeddedServletContainer(
+				mergeInitializers(initializers), getPort()));
 		return this.container;
 	}
 
@@ -119,8 +124,30 @@ public class MockEmbeddedServletContainerFactory extends
 								return registeredFilter.getRegistration();
 							}
 						});
+				final Map<String, String> initParameters = new HashMap<String, String>();
+				given(this.servletContext.setInitParameter(anyString(), anyString()))
+						.will(new Answer<Void>() {
+							@Override
+							public Void answer(InvocationOnMock invocation)
+									throws Throwable {
+								initParameters.put(
+										invocation.getArgumentAt(0, String.class),
+										invocation.getArgumentAt(1, String.class));
+								return null;
+							}
+
+						});
 				given(this.servletContext.getInitParameterNames()).willReturn(
-						MockEmbeddedServletContainer.<String> emptyEnumeration());
+						Collections.enumeration(initParameters.keySet()));
+				given(this.servletContext.getInitParameter(anyString())).willAnswer(
+						new Answer<String>() {
+							@Override
+							public String answer(InvocationOnMock invocation)
+									throws Throwable {
+								return initParameters.get(invocation.getArgumentAt(0,
+										String.class));
+							}
+						});
 				given(this.servletContext.getAttributeNames()).willReturn(
 						MockEmbeddedServletContainer.<String> emptyEnumeration());
 				given(this.servletContext.getNamedDispatcher("default")).willReturn(