web/src/main/java/org/springframework/security/web/authentication/ExceptionMappingAuthenticationFailureHandler.java
public void setExceptionMappings(Map<?, ?> failureUrlMap) {
		this.failureUrlMap.clear();
		for (Map.Entry<?, ?> entry : failureUrlMap.entrySet()) {
			Object exception = entry.getKey();
			Object url = entry.getValue();
			Assert.isInstanceOf(String.class, exception,
					"Exception key must be a String (the exception classname).");
			Assert.isInstanceOf(String.class, url, "URL must be a String");
			Assert.isTrue(UrlUtils.isValidRedirectUrl((String) url),
					() -> "Not a valid redirect URL: " + url);
			this.failureUrlMap.put((String) exception, (String) url);
		}
	}
public void setExceptionMappings(Map<?, ?> failureUrlMap) {
		this.failureUrlMap.clear();
		for (Map.Entry<?, ?> entry : failureUrlMap.entrySet()) {
			Object exception = entry.getKey();
			Object url = entry.getValue();
			Assert.isInstanceOf(String.class, exception,
					"Exception key must be a String (the exception classname).");
			Assert.isInstanceOf(String.class, url, "URL must be a String");
			Assert.isTrue(UrlUtils.isValidRedirectUrl((String) url),
					() -> "Not a valid redirect URL: " + url);
			this.failureUrlMap.put((String) exception, (String) url);
		}
	}
Sets the map of exception types (by name) to URLs.

@param failureUrlMap the map keyed by the fully-qualified name of the exception
class, with the corresponding failure URL as the value.

@throws IllegalArgumentException if the entries are not Strings or the URL is not
valid.