Even this question is already answered I want to show you my solution.
We use Spring Security for LDAP authentication, so we have these two configuration classes:
@EnableWebSecurity
@EnableGlobalMethodSecurity(securedEnabled = true, proxyTargetClass = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter
{
    @Override
    protected void configure(HttpSecurity http) throws Exception
    {
        // @formatter:off
        http
            .authorizeRequests()
                .anyRequest().authenticated() // Alle Requests erfordern einen Login...
                .and()
            .formLogin().loginPage("/login").defaultSuccessUrl("/#!").permitAll() // http://docs.spring.io/spring-security/site/docs/4.0.3.RELEASE/reference/htmlsingle/#jc-form
                .and()
            .logout().permitAll() // http://docs.spring.io/spring-security/site/docs/4.0.3.RELEASE/reference/htmlsingle/#jc-logout
                .and()
            .csrf().disable(); // CSRF (https://docs.spring.io/spring-security/site/docs/current/reference/html/csrf.html) wird von Vaadin selbst gehandhabt!
        // @formatter:on
    }
    /**
     * @see http://stackoverflow.com/questions/34944617/java-config-for-spring-security-with-vaadin/35212403#35212403
     */
    @Override
    public void configure(WebSecurity web) throws Exception
    {
        // @formatter:off
        web
            .ignoring()
                .antMatchers("/resources/**", "/VAADIN/**");
        // @formatter:on
    }
}
@Configuration
public class SecurityConfigActiveDirectory
{
    @Value("${ldap.url}")
    String ldapUrl;
    @Value("${ldap.domain}")
    String ldapDomain;
    @Bean
    public AuthenticationManager authenticationManager()
    {
        ActiveDirectoryLdapAuthenticationProvider adProvider = new ActiveDirectoryLdapAuthenticationProvider(ldapDomain, ldapUrl);
        adProvider.setConvertSubErrorCodesToExceptions(true);
        adProvider.setUseAuthenticationRequestCredentials(true);
        adProvider.setAuthoritiesMapper(getAuthorityMapper());
        return new ProviderManager(Arrays.asList(adProvider));
    }
    private static SimpleAuthorityMapper getAuthorityMapper()
    {
        SimpleAuthorityMapper mapper = new SimpleAuthorityMapper();
        mapper.setConvertToUpperCase(true);
        return mapper;
    }
}
SecurityConfig class defines which pages should be protected in our web application and SecurityConfigActiveDirectory defines the LDAP authentication provider.
ldap.domain can be something like private.myTest.de and ldap.url something like ldap://myLdapHost.private.myTest.de:389.
Cheers!