How to log failed login attempts in my web application?

I have a web application which uses Weblogic. I want to login information in a log file. However, how to log failed login attempts? In the web.xml, I defined like this:

 <login-config>
    <auth-method>FORM</auth-method>
    <form-login-config>
        <form-login-page>/login-success.html</form-login-page>
        <form-error-page>/login-fail.html</form-error-page>
    </form-login-config>
</login-config>

Thank you very much.