Refine null-safety in the spring-webmvc module

Closes gh-34164

Author: sdeleuze

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/ResourceChainRegistration.java

@@ -65,7 +65,7 @@ public ResourceChainRegistration(boolean cacheResources) {
 		this(cacheResources, (cacheResources ? new ConcurrentMapCache(DEFAULT_CACHE_NAME) : null));
 	}
 
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	public ResourceChainRegistration(boolean cacheResources, @Nullable Cache cache) {
 		Assert.isTrue(!cacheResources || cache != null, "'cache' is required when cacheResources=true");
 		if (cacheResources) {

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

@@ -69,7 +69,7 @@ public DefaultServerResponseBuilder(HttpStatusCode status) {
 	}
 
 	@Override
-	@SuppressWarnings("NullAway") // TODO NullAway bug potentially due to the recursive generic type
+	@SuppressWarnings("NullAway") // https://github.com/uber/NullAway/issues/1113
 	public ServerResponse.BodyBuilder header(String headerName, @Nullable String... headerValues) {
 		Assert.notNull(headerName, "HeaderName must not be null");
 		for (String headerValue : headerValues) {

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

@@ -436,7 +436,7 @@ protected void handlerMethodsInitialized(Map<T, HandlerMethod> handlerMethods) {
 		}
 	}
 
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
 		for (T mapping : mappings) {
 			T match = getMatchingMapping(mapping, request);

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

@@ -271,7 +271,7 @@ private String getHandlerDescription(Object handler) {
 	 * @return a matching handler, or {@code null} if not found
 	 * @since 5.3
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected @Nullable Object lookupHandler(
 			RequestPath path, String lookupPath, HttpServletRequest request) throws Exception {
 

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

@@ -233,7 +233,7 @@ private int getEndPathIndex(String lookupPath) {
 	 * @param lookupPath the lookup path to check
 	 * @return the resolved public URL path, or {@code null} if unresolved
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	public final @Nullable String getForLookupPath(String lookupPath) {
 		// Clean duplicate slashes or pathWithinPattern won't match lookupPath
 		String previous;

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

@@ -301,7 +301,7 @@ public void release() {
 	 * Resolve the specified message into a concrete message String.
 	 * The returned message String should be unescaped.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected String resolveMessage() throws JspException, NoSuchMessageException {
 		MessageSource messageSource = getMessageSource();