Update javadoc

Signed-off-by: Tran Ngoc Nhan <ngocnhan.tran1996@gmail.com>

Author: ngocnhan-tran1996

core/src/main/java/org/springframework/security/access/expression/SecurityExpressionRoot.java

@@ -229,7 +229,7 @@ private boolean isGranted(AuthorizationManager<T> authorizationManager) {
 	/**
 	 * Convenience method to access {@link Authentication#getPrincipal()} from
 	 * {@link #getAuthentication()}
-	 * @return
+	 * @return the {@code Principal} being authenticated or the authenticated principal after authentication.
 	 */
 	public @Nullable Object getPrincipal() {
 		return getAuthentication().getPrincipal();

core/src/main/java/org/springframework/security/authorization/AuthorityAuthorizationManager.java

@@ -168,6 +168,7 @@ public static <T> AuthorityAuthorizationManager<T> hasScope(String scope) {
 	 *
 	 */
 	public static <T> AuthorityAuthorizationManager<T> hasAnyScope(String... scopes) {
+		Assert.notNull(scopes, "scopes cannot be null");
 		String[] mappedScopes = new String[scopes.length];
 		for (int i = 0; i < scopes.length; i++) {
 			assertScope(scopes[i]);
@@ -189,7 +190,7 @@ private static String[] toNamedRolesArray(String rolePrefix, String[] roles) {
 	}
 
 	private static void assertScope(String scope) {
-		Assert.notNull(scope, "role cannot be null");
+		Assert.notNull(scope, "scope cannot be null");
 		Assert.isTrue(!scope.startsWith("SCOPE_"),
 				() -> scope + " should not start with SCOPE_ since SCOPE_"
 						+ " is automatically prepended when using hasScope and hasAnyScope. Consider using "