Avoid creating a new EmbeddedServletContainerFactory for websockets

User can now also switch off and customize the websockets customizer by adding
a bean named "websocketContainerCustomizer".

Fixes gh-479

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/aop/AopAutoConfiguration.java

@@ -18,20 +18,22 @@ package org.springframework.boot.autoconfigure.aop;
 
 import org.aspectj.lang.annotation.Aspect;
 import org.aspectj.lang.reflect.Advice;
-import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.EnableAspectJAutoProxy;
 
 /**
- *
- * <p> {@link org.springframework.boot.autoconfigure.EnableAutoConfiguration Auto-configuration}
- * for Spring's  AOP support. Equivalent to enabling {@link org.springframework.context.annotation.EnableAspectJAutoProxy}
- * in your configuration. The configuration will not be activated if {@literal spring.aop.auto=false}.
- * The {@literal proxyTargetClass} attribute will be {@literal false}, by default, but can be overridden by
- * specifying {@literal spring.aop.proxyTargetClass=true}.
- *
+ * 
+ * <p>
+ * {@link org.springframework.boot.autoconfigure.EnableAutoConfiguration
+ * Auto-configuration} for Spring's AOP support. Equivalent to enabling
+ * {@link org.springframework.context.annotation.EnableAspectJAutoProxy} in your
+ * configuration. The configuration will not be activated if
+ * {@literal spring.aop.auto=false}. The {@literal proxyTargetClass} attribute will be
+ * {@literal false}, by default, but can be overridden by specifying
+ * {@literal spring.aop.proxyTargetClass=true}.
+ * 
  * @author Dave Syer
  * @author Josh Long
  * @see EnableAspectJAutoProxy

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

@@ -53,8 +53,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 
 	private Integer sessionTimeout;
 
-	@NotNull
-	private String contextPath = "";
+	private String contextPath;
 
 	@NotNull
 	private String servletPath = "/";

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/websocket/WebSocketAutoConfiguration.java

@@ -23,7 +23,11 @@ import org.apache.catalina.deploy.ApplicationListener;
 import org.apache.catalina.startup.Tomcat;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration;
+import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
+import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
+import org.springframework.boot.context.embedded.tomcat.TomcatContextCustomizer;
 import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -47,14 +51,31 @@ public class WebSocketAutoConfiguration {
 			"org.apache.tomcat.websocket.server.WsContextListener", false);
 
 	@Bean
-	public TomcatEmbeddedServletContainerFactory tomcatEmbeddedServletContainerFactory() {
-		TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory() {
+	@ConditionalOnMissingBean(name = "websocketContainerCustomizer")
+	public EmbeddedServletContainerCustomizer websocketContainerCustomizer() {
+
+		EmbeddedServletContainerCustomizer customizer = new EmbeddedServletContainerCustomizer() {
+
 			@Override
-			protected void postProcessContext(Context context) {
-				context.addApplicationListener(WS_APPLICATION_LISTENER);
+			public void customize(ConfigurableEmbeddedServletContainer container) {
+				if (!(container instanceof TomcatEmbeddedServletContainerFactory)) {
+					throw new IllegalStateException(
+							"Websockets are currently only supported in Tomcat (found "
+									+ container.getClass() + ")");
+				}
+				((TomcatEmbeddedServletContainerFactory) container)
+						.addContextCustomizers(new TomcatContextCustomizer() {
+							@Override
+							public void customize(Context context) {
+								context.addApplicationListener(WS_APPLICATION_LISTENER);
+							}
+						});
 			}
+
 		};
-		return factory;
+
+		return customizer;
+
 	}
 
 }

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

@@ -29,6 +29,7 @@ import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletCont
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
 /**
@@ -75,7 +76,7 @@ public class ServerPropertiesTests {
 	public void testCustomizeTomcat() throws Exception {
 		ConfigurableEmbeddedServletContainer factory = mock(ConfigurableEmbeddedServletContainer.class);
 		this.properties.customize(factory);
-		verify(factory).setContextPath("");
+		verify(factory, times(0)).setContextPath("");
 	}
 
 	@Test