Custom Authentication provider with Spring Security and Java Config

The following does what you need (CustomAuthenticationProvider is your implementation which needs to be managed by Spring)

@Configuration
@EnableWebMvcSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private CustomAuthenticationProvider customAuthenticationProvider;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        /**
         * Do your stuff here
         */
    }

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.authenticationProvider(customAuthenticationProvider);
    }
}