code: public void updateSecureIdentitySecurityDomainCredentials(String securityDomainName, String username,
              String password) throws Exception {
  
          Address addr = Address.root().add(SUBSYSTEM, SUBSYSTEM_SECURITY, SECURITY_DOMAIN, securityDomainName,
                  AUTHENTICATION, CLASSIC);
  
          ModelNode loginModule = new ModelNode();
          loginModule.get(CODE).set("SecureIdentity");
          loginModule.get(FLAG).set("required");
          ModelNode moduleOptions = loginModule.get(MODULE_OPTIONS);
          moduleOptions.setEmptyList();
          addPossibleExpression(moduleOptions, USERNAME, username);
          addPossibleExpression(moduleOptions, PASSWORD, password);
  
          // login modules attribute must be a list - we only have one item in it, the loginModule
          ModelNode loginModuleList = new ModelNode();
          loginModuleList.setEmptyList();
          loginModuleList.add(loginModule);
  
          final ModelNode op = createRequest(WRITE_ATTRIBUTE, addr);
          op.get(NAME).set(LOGIN_MODULES);
          op.get(VALUE).set(loginModuleList);
  
          ModelNode results = execute(op);
          if (!isSuccess(results)) {
              throw new FailureException(results, "Failed to update credentials for security domain ["
                      + securityDomainName + "]");
          }
  
          return;
      }
docs: Given the name of an existing security domain that uses the SecureIdentity authentication method,
  this updates that domain with the new credentials. Use this to change credentials if you don't
  want to use expressions as the username or password entry (in some cases you can't, see the JIRA
  https://issues.jboss.org/browse/AS7-5177 for more info).
  
  @param securityDomainName the name of the security domain whose credentials are to change
  @param username the new username to be associated with the security domain
  @param password the new value of the password to store in the configuration
  (e.g. the obfuscated password itself)
  
  @throws Exception if failed to update security domain