Consistently check DispatcherType to avoid NPE in tests

Closes gh-26602

spring-web/src/main/java/org/springframework/web/filter/OncePerRequestFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -145,7 +145,7 @@ public abstract class OncePerRequestFilter extends GenericFilterBean {
 	 * @see WebAsyncManager#hasConcurrentResult()
 	 */
 	protected boolean isAsyncDispatch(HttpServletRequest request) {
-		return request.getDispatcherType().equals(DispatcherType.ASYNC);
+		return DispatcherType.ASYNC.equals(request.getDispatcherType());
 	}
 
 	/**

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

@@ -986,8 +986,8 @@ public class DispatcherServlet extends FrameworkServlet {
 
 			String queryString = request.getQueryString();
 			String queryClause = (StringUtils.hasLength(queryString) ? "?" + queryString : "");
-			String dispatchType = (!request.getDispatcherType().equals(DispatcherType.REQUEST) ?
-					"\"" + request.getDispatcherType().name() + "\" dispatch for " : "");
+			String dispatchType = (!DispatcherType.REQUEST.equals(request.getDispatcherType()) ?
+					"\"" + request.getDispatcherType() + "\" dispatch for " : "");
 			String message = (dispatchType + request.getMethod() + " \"" + getRequestUri(request) +
 					queryClause + "\", parameters={" + params + "}");
 
@@ -1185,7 +1185,7 @@ public class DispatcherServlet extends FrameworkServlet {
 	protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
 		if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
 			if (WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class) != null) {
-				if (request.getDispatcherType().equals(DispatcherType.REQUEST)) {
+				if (DispatcherType.REQUEST.equals(request.getDispatcherType())) {
 					logger.trace("Request already resolved to MultipartHttpServletRequest, e.g. by MultipartFilter");
 				}
 			}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -1084,8 +1084,8 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 			return;
 		}
 
-		String dispatchType = request.getDispatcherType().name();
-		boolean initialDispatch = request.getDispatcherType().equals(DispatcherType.REQUEST);
+		DispatcherType dispatchType = request.getDispatcherType();
+		boolean initialDispatch = DispatcherType.REQUEST.equals(request.getDispatcherType());
 
 		if (failureCause != null) {
 			if (!initialDispatch) {

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

@@ -519,7 +519,7 @@ public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
 		if (logger.isTraceEnabled()) {
 			logger.trace("Mapped to " + handler);
 		}
-		else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
+		else if (logger.isDebugEnabled() && !DispatcherType.ASYNC.equals(request.getDispatcherType())) {
 			logger.debug("Mapped to " + executionChain.getHandler());
 		}