Make DispatcherServlet.properties loading lazy

With spring-projects#25209, DispatcherServlet.properties loading and parsing
will be useless for most of use cases, and it requires
configuration on GraalVM native images.

The purpose of this issue to make such loading and parsing lazy,
only invoked in getDefaultStrategies() if needed.

Closes spring-projectsgh-25257

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

@@ -157,6 +157,7 @@
  * @author Rob Harrop
  * @author Chris Beams
  * @author Rossen Stoyanchev
+ * @author Sebastien Deleuze
  * @see org.springframework.web.HttpRequestHandler
  * @see org.springframework.web.servlet.mvc.Controller
  * @see org.springframework.web.context.ContextLoaderListener
@@ -280,20 +281,9 @@ public class DispatcherServlet extends FrameworkServlet {
 	/** Additional logger to use when no mapped handler is found for a request. */
 	protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY);
 
-	private static final Properties defaultStrategies;
-
-	static {
-		// Load default strategy implementations from properties file.
-		// This is currently strictly internal and not meant to be customized
-		// by application developers.
-		try {
-			ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
-			defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
-		}
-		catch (IOException ex) {
-			throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
-		}
-	}
+	/** Store default strategy implementations. */
+	@Nullable
+	private static Properties defaultStrategies;
 
 	/** Detect all HandlerMappings or just expect "handlerMapping" bean?. */
 	private boolean detectAllHandlerMappings = true;
@@ -869,6 +859,19 @@ protected <T> T getDefaultStrategy(ApplicationContext context, Class<T> strategy
 	 */
 	@SuppressWarnings("unchecked")
 	protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
+		if (defaultStrategies == null) {
+			try {
+				// Load default strategy implementations from properties file.
+				// This is currently strictly internal and not meant to be customized
+				// by application developers.
+				ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
+				defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
+			}
+		}
+
 		String key = strategyInterface.getName();
 		String value = defaultStrategies.getProperty(key);
 		if (value != null) {