在Spring Security 3.0中，应将<ldap-authentication-provider>(以及<authentication-provider>)放在<authentication-manager>中:

In Spring Security 3.0, <ldap-authentication-provider> (as well as <authentication-provider>) should be placed inside <authentication-manager>:

<authentication-manager>
    <ldap-authentication-provider user-search-filter="(samaccountname={0})" user-search-base="dc=company,dc=com"/> 
</authentication-manager>