web/src/main/java/org/springframework/security/web/authentication/SimpleUrlAuthenticationFailureHandler.java
public void setDefaultFailureUrl(String defaultFailureUrl) {
		Assert.isTrue(UrlUtils.isValidRedirectUrl(defaultFailureUrl),
				() -> "'" + defaultFailureUrl + "' is not a valid redirect URL");
		this.defaultFailureUrl = defaultFailureUrl;
	}
public void setDefaultFailureUrl(String defaultFailureUrl) {
		Assert.isTrue(UrlUtils.isValidRedirectUrl(defaultFailureUrl),
				() -> "'" + defaultFailureUrl + "' is not a valid redirect URL");
		this.defaultFailureUrl = defaultFailureUrl;
	}
The URL which will be used as the failure destination.

@param defaultFailureUrl the failure URL, for example "/loginFailed.jsp".