Throw IllegalStateException for invalid port in HierarchicalUriComponents

Prior to this commit, getPort() in HierarchicalUriComponents threw a
NumberFormatException for an invalid port supplied as a String, which
was inconsistent with exception handling elsewhere in the class as well
as within the same method.

This commit introduces a try-catch block in getPort() to consistently
throw IllegalStateExceptions for ports that cannot be parsed.

Closes gh-28521

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -46,6 +46,7 @@ import org.springframework.util.StringUtils;
  * @author Juergen Hoeller
  * @author Rossen Stoyanchev
  * @author Phillip Webb
+ * @author Sam Brannen
  * @since 3.1.3
  * @see <a href="https://tools.ietf.org/html/rfc3986#section-1.2.3">Hierarchical URIs</a>
  */
@@ -192,7 +193,12 @@ final class HierarchicalUriComponents extends UriComponents {
 			throw new IllegalStateException(
 					"The port contains a URI variable but has not been expanded yet: " + this.port);
 		}
-		return Integer.parseInt(this.port);
+		try {
+			return Integer.parseInt(this.port);
+		}
+		catch (NumberFormatException ex) {
+			throw new IllegalStateException("The port must be an integer: " + this.port);
+		}
 	}
 
 	@Override