spring-boot-rest/spring-security-mvc-boot/spring-security-mvc-boot-default/src/main/java/com/baeldung/security/CustomUserDetailsService.java

package com.baeldung.security;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;
import org.springframework.web.context.WebApplicationContext;

import com.baeldung.data.repositories.UserRepository;
import com.baeldung.models.AppUser;

@Service
public class CustomUserDetailsService implements UserDetailsService {

    @Autowired
    private WebApplicationContext applicationContext;
    private UserRepository userRepository;

    public CustomUserDetailsService() {
        super();
    }

    @PostConstruct
    public void completeSetup() {
        userRepository = applicationContext.getBean(UserRepository.class);
    }

    @Override
    public UserDetails loadUserByUsername(final String username) {
        final AppUser appUser = userRepository.findByUsername(username);
        if (appUser == null) {
            throw new UsernameNotFoundException(username);
        }
        return new AppUserPrincipal(appUser);
    }

}