Add Username Property to Exception

Closes gh-17179

core/src/main/java/org/springframework/security/core/userdetails/UsernameNotFoundException.java

@@ -31,12 +31,15 @@ public class UsernameNotFoundException extends AuthenticationException {
 	@Serial
 	private static final long serialVersionUID = 1410688585992297006L;
 
+	private final String name;
+
 	/**
 	 * Constructs a <code>UsernameNotFoundException</code> with the specified message.
 	 * @param msg the detail message.
 	 */
 	public UsernameNotFoundException(String msg) {
 		super(msg);
+		this.name = null;
 	}
 
 	/**
@@ -47,6 +50,42 @@ public class UsernameNotFoundException extends AuthenticationException {
 	 */
 	public UsernameNotFoundException(String msg, Throwable cause) {
 		super(msg, cause);
+		this.name = null;
+	}
+
+	private UsernameNotFoundException(String msg, String name, Throwable cause) {
+		super(msg, cause);
+		this.name = name;
+	}
+
+	/**
+	 * Construct an exception based on a specific username
+	 * @param username the invalid username
+	 * @return the {@link UsernameNotFoundException}
+	 * @since 7.0
+	 */
+	public static UsernameNotFoundException fromUsername(String username) {
+		return fromUsername(username, null);
+	}
+
+	/**
+	 * Construct an exception based on a specific username
+	 * @param username the invalid username
+	 * @param cause any underlying cause
+	 * @return the {@link UsernameNotFoundException}
+	 * @since 7.0
+	 */
+	public static UsernameNotFoundException fromUsername(String username, Throwable cause) {
+		return new UsernameNotFoundException("user not found", username, cause);
+	}
+
+	/**
+	 * Get the username that couldn't be found
+	 * @return the username
+	 * @since 7.0
+	 */
+	public String getName() {
+		return this.name;
 	}
 
 }