Make StringUtils::pathEquals Null-Safe

[sairohith2605]

This PR introduces a tiny patch for the method StringUtils.pathEquals() that short-circuits into a false result if any or both of the parameters of path are null. This aims to prevent a NullPointerException when cleanPath() returns null when the supplied path String does not have any length.

[sbrannen]

Hi @sairohith2605,

Congratulations on submitting your first PR for the Spring Framework! 👍

Unfortunately, I need to decline the proposal for the following reasons.

1. Supplying a null path to StringUtils.pathEquals(...) is not a supported use case.
2. The org.springframework.util package (see package-info.java) is annotated with @NullMarked.
3. Consequently, null is not a supported argument value unless a given parameter is annotated with @Nullable.
4. Neither path1 nor path2 is annotated with @Nullable.

It is therefore the responsibility of the caller to ensure that pathEquals(...) is not invoked with a null argument.

Note that we rely on the NullAway build plugin for Gradle as well as IDE support to ensure that we do not supply a null value for one of those arguments. For example, in WebUtils you can see that we verify that both arguments are not null.

spring-framework/spring-web/src/main/java/org/springframework/web/util/WebUtils.java

Lines 241 to 252 in 8a71911

	if (root == null) {
	throw new IllegalStateException(
	"Cannot set web app root system property when WAR file is not expanded");
	}
	String param = servletContext.getInitParameter(WEB_APP_ROOT_KEY_PARAM);
	String key = (param != null ? param : DEFAULT_WEB_APP_ROOT_KEY);
	String oldValue = System.getProperty(key);
	if (oldValue != null && !StringUtils.pathEquals(oldValue, root)) {
	throw new IllegalStateException("Web app root system property already set to different value: '" +
	key + "' = [" + oldValue + "] instead of [" + root + "] - " +
	"Choose unique values for the 'webAppRootKey' context-param in your web.xml files!");
	}

In light of the above, I am closing this PR.

Thanks anyway