<s:action name="doLogin" executeResult="true"></s:action>

<action name="doLogin" class="siteLoginAction">
    <result name="input">/WEB-INF/jsp/sitePages/siteLogin.jsp</result>
    <result name="success">/WEB-INF/jsp/sitePages/siteLogin.jsp</result>
</action>

@Override
public void validate() {
    String username = siteUser.getSiteUserUsername();
    String password = siteUser.getSiteUserPassword();

    if (StringUtils.isEmpty(username) || StringUtils.isEmpty(password)) {
        addFieldError("siteUser.siteUserUsername", "Invalid login");
    } else if (!siteUserService.checkLoginExists(username, password, getBlogSiteUrl())) {
        addFieldError("siteUser.siteUserPassword", "Invalid login");
    }
}