Spring Security 3: Salting password issue

I have got an simple application made in which I am able to register users and authenticate them. I've got the passwords encoded using and successfully able to authenticate them. I am using Spring 3, Spring Security 3 and Hibernate 3 in my application.

Now I want to salt their passwords with the ID of the user but I am not able to achieve this functionality. Could someone help me achieve it? I've been trying to do it for quite some time but ain't able to get it done.

Here is the code I've got for salting users with their ID and authenticating them.

xyz-security.xml

<http auto-config="true" use-expressions="true">
    <intercept-url pattern="/welcome.do" access="hasRole('ROLE_USER')" /> 
    <form-login login-page="/login.do" authentication-failure-url="/login.do?login_error=1"/>       
    <logout invalidate-session="true" logout-url="/logout" logout-success-url="/"/>
</http>

<beans:bean id="daoAuthenticationProvider"  class="org.springframework.security.authentication.dao.DaoAuthenticationProvider">
    <beans:property name="userDetailsService" ref="userDetailsService"/>
</beans:bean>

<beans:bean id="authenticationManager" class="org.springframework.security.authentication.ProviderManager">
    <beans:property name="providers">
        <beans:list>
            <beans:ref local="daoAuthenticationProvider" />
        </beans:list>
    </beans:property>
</beans:bean>

<authentication-manager>
    <authentication-provider user-service-ref="userDetailsService">
        <password-encoder ref="passwordEncoder">                
            <salt-source ref="saltSource"/>
            </password-encoder>
    </authentication-provider>
</authentication-manager>

<!-- For hashing and salting user passwords -->
<beans:bean id="passwordEncoder" class="org.springframework.security