public class CustomFreeMarkerLoginFormsProvider extends FreeMarkerLoginFormsProvider {
/**
* Mapping between password policy provider IDs and custom messages
* Note: contains only standard policies that must be displayed in the UI
*/
private final Map<String, String> policyPropertyMessages = Map.of(
LengthPasswordPolicyProviderFactory.ID, MINIMUM_LENGTH_MESSAGE,
MaximumLengthPasswordPolicyProviderFactory.ID, MAXIMUM_LENGTH_MESSAGE,
DigitsPasswordPolicyProviderFactory.ID, MINIMUM_DIGIT_MESSAGE,
SpecialCharsPasswordPolicyProviderFactory.ID, MINIMUM_SPECIAL_CHAR_MESSAGE,
UpperCasePasswordPolicyProviderFactory.ID, MINIMUM_UPPERCASE_MESSAGE,
LowerCasePasswordPolicyProviderFactory.ID, MINIMUM_LOWERCASE_MESSAGE,
NotUsernamePasswordPolicyProviderFactory.ID, NOT_USERNAME_MESSAGE,
NotContainsUsernamePasswordPolicyProviderFactory.ID, NOT_CONTAINS_USERNAME_MESSAGE,
NotEmailPasswordPolicyProviderFactory.ID, NOT_EMAIL_MESSAGE
);

[...]

@Override
protected void createCommonAttributes(Theme theme, Locale locale, Properties messagesBundle,
UriBuilder baseUriBuilder, LoginFormsPages page) {
super.createCommonAttributes(theme, locale, messagesBundle, baseUriBuilder, page);
if (realm != null && realm.getPasswordPolicy() != null) {
attributes.put("passwordPolicies", getPasswordPolicyMessages(realm.getPasswordPolicy(), messagesBundle));
}}

[...]

private Map<String, String> getPasswordPolicyMessages(PasswordPolicy passwordPolicy, Properties messagesBundle) {
Map<String, String> policyMessages = new HashMap<>();
PasswordPolicy.Builder builder = passwordPolicy.toBuilder();
for (String policyName : passwordPolicy.getPolicies()) {
var value = builder.get(policyName);
String message = extractPolicyMessage(policyName, value, messagesBundle);
if (message != null) {
policyMessages.put(policyName, message);
}
}
return policyMessages;
}

[...]

/**
* Extracts a message for a given password policy from the messages bundle
* Note: Policy message is constructed by replacing the {0} placeholder with the policy value
*/
private String extractPolicyMessage(String policy, String value, Properties messagesBundle) {
String property = policyPropertyMessages.get(policy);
if (property == null) {
return null;
}
String policyMessage = messagesBundle.getProperty(property);
return policyMessage != null ? policyMessage.replace("{0}", value) : null;
}