How to connect LDAP With username and password?

I have my Ldap working the only issue i'm facing was when I try to login with email that is when I land in the else part in the below code. If my username is different from email then it throws error. i.e if my email is '[email protected]' and my username is 'saurakumar' then it will through invalid username password error. As internally I'm using username to make email i.e if the user login with name 'karan' then i'm expecting the email to be karan @gmail.com which is not true in many scenario and the Authentication fails. I'm looking for some solution wherein I can login either via email or via username I'll be able to authenticate user. Below is the snippet of my code. Please suggest?

    ldapEnv.put(Context.INITIAL_CONTEXT_FACTORY, initialContextFactory);
    ldapEnv.put(Context.PROVIDER_URL, url);
    ldapEnv.remove(Context.SECURITY_PROTOCOL);
    if (email == null) {
        lContext = new InitialLdapContext(ldapEnv, null);
        entryResult = searchUserEntry(lContext, user, searchCtrls);
        final String usrDN = ((Context) entryResult.getObject()).getNameInNamespace();

        lContext.addToEnvironment(Context.SECURITY_AUTHENTICATION, "simple");
        lContext.addToEnvironment(Context.SECURITY_PRINCIPAL, usrDN);
        lContext.addToEnvironment(Context.SECURITY_CREDENTIALS, pass);
        lContext.reconnect(null);
    } else {
            ldapEnv.put(Context.SECURITY_PRINCIPAL, email);
            ldapEnv.put(Context.SECURITY_CREDENTIALS, credentials);
            lContext = new InitialLdapContext(ldapEnv, null);
            return lContext;
        searchUserEntry(lContext, user, searchCtrls);
    }