Ensure that lazy session id generator is initialized by manager

Closes gh-6679

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

@@ -17,6 +17,7 @@
 package org.springframework.boot.context.embedded.tomcat;
 
 import org.apache.catalina.Container;
+import org.apache.catalina.Manager;
 import org.apache.catalina.core.StandardContext;
 
 import org.springframework.util.ClassUtils;
@@ -49,6 +50,14 @@ class TomcatEmbeddedContext extends StandardContext {
 		return super.loadOnStartup(children);
 	}
 
+	@Override
+	public void setManager(Manager manager) {
+		if (manager != null) {
+			manager.setSessionIdGenerator(new LazySessionIdGenerator());
+		}
+		super.setManager(manager);
+	}
+
 	public void deferredLoadOnStartup() {
 		// Some older Servlet frameworks (e.g. Struts, BIRT) use the Thread context class
 		// loader to create servlet instances in this phase. If they do that and then try

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

@@ -46,7 +46,6 @@ import org.apache.catalina.Valve;
 import org.apache.catalina.Wrapper;
 import org.apache.catalina.connector.Connector;
 import org.apache.catalina.loader.WebappLoader;
-import org.apache.catalina.session.ManagerBase;
 import org.apache.catalina.session.StandardManager;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.startup.Tomcat.FixContextListener;
@@ -488,7 +487,6 @@ public class TomcatEmbeddedServletContainerFactory
 		else {
 			context.addLifecycleListener(new DisablePersistSessionListener());
 		}
-		context.addLifecycleListener(new LazySessionIdGeneratorListener());
 	}
 
 	private void configurePersistSession(Manager manager) {
@@ -830,20 +828,4 @@ public class TomcatEmbeddedServletContainerFactory
 
 	}
 
-	private static class LazySessionIdGeneratorListener implements LifecycleListener {
-
-		@Override
-		public void lifecycleEvent(LifecycleEvent event) {
-			if (event.getType().equals(Lifecycle.START_EVENT)) {
-				Context context = (Context) event.getLifecycle();
-				Manager manager = context.getManager();
-				if (manager instanceof ManagerBase) {
-					((ManagerBase) manager)
-							.setSessionIdGenerator(new LazySessionIdGenerator());
-				}
-			}
-		}
-
-	}
-
 }

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

@@ -34,6 +34,7 @@ import org.apache.catalina.LifecycleEvent;
 import org.apache.catalina.LifecycleListener;
 import org.apache.catalina.LifecycleState;
 import org.apache.catalina.Service;
+import org.apache.catalina.SessionIdGenerator;
 import org.apache.catalina.Valve;
 import org.apache.catalina.Wrapper;
 import org.apache.catalina.connector.Connector;
@@ -441,6 +442,25 @@ public class TomcatEmbeddedServletContainerFactoryTests
 		assertThat(getCharset(Locale.FRENCH).toString()).isEqualTo("UTF-8");
 	}
 
+	@Test
+	public void sessionIdGeneratorIsConfiguredWithAttributesFromTheManager() {
+		System.setProperty("jvmRoute", "test");
+		try {
+			TomcatEmbeddedServletContainerFactory factory = getFactory();
+			this.container = factory.getEmbeddedServletContainer();
+			this.container.start();
+		}
+		finally {
+			System.clearProperty("jvmRoute");
+		}
+		Tomcat tomcat = ((TomcatEmbeddedServletContainer) this.container).getTomcat();
+		Context context = (Context) tomcat.getHost().findChildren()[0];
+		SessionIdGenerator sessionIdGenerator = context.getManager()
+				.getSessionIdGenerator();
+		assertThat(sessionIdGenerator).isInstanceOf(LazySessionIdGenerator.class);
+		assertThat(sessionIdGenerator.getJvmRoute()).isEqualTo("test");
+	}
+
 	@Override
 	protected Wrapper getJspServlet() {
 		Container context = ((TomcatEmbeddedServletContainer) this.container).getTomcat()