AbstractDispatcherServletInitializer allows for registering any FrameworkServlet subclass

Issue: SPR-13616

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

@@ -32,6 +32,7 @@ import org.springframework.util.ObjectUtils;
 import org.springframework.web.context.AbstractContextLoaderInitializer;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.servlet.DispatcherServlet;
+import org.springframework.web.servlet.FrameworkServlet;
 
 /**
  * Base class for {@link org.springframework.web.WebApplicationInitializer}
@@ -90,7 +91,7 @@ public abstract class AbstractDispatcherServletInitializer extends AbstractConte
 				"createServletApplicationContext() did not return an application " +
 				"context for servlet [" + servletName + "]");
 
-		DispatcherServlet dispatcherServlet = createDispatcherServlet(servletAppContext);
+		FrameworkServlet dispatcherServlet = createDispatcherServlet(servletAppContext);
 		dispatcherServlet.setContextInitializers(getServletApplicationContextInitializers());
 
 		ServletRegistration.Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);
@@ -132,9 +133,12 @@ public abstract class AbstractDispatcherServletInitializer extends AbstractConte
 	protected abstract WebApplicationContext createServletApplicationContext();
 
 	/**
-	 * Create a {@link DispatcherServlet} with the specified {@link WebApplicationContext}.
+	 * Create a {@link DispatcherServlet} (or other kind of {@link FrameworkServlet}-derived
+	 * dispatcher) with the specified {@link WebApplicationContext}.
+	 * <p>Note: This allows for any {@link FrameworkServlet} subclass as of 4.2.3.
+	 * Previously, it insisted on returning a {@link DispatcherServlet} or subclass thereof.
 	 */
-	protected DispatcherServlet createDispatcherServlet(WebApplicationContext servletAppContext) {
+	protected FrameworkServlet createDispatcherServlet(WebApplicationContext servletAppContext) {
 		return new DispatcherServlet(servletAppContext);
 	}