My userrepo is null so can't use findbyusername is userdetailsservice

I have injected my userrepo with @Autowired. I can signup and add users to the database without any problem. However when I have to authenticate against users in my database I get this issue

Caused by: java.lang.NullPointerException: Cannot invoke "com.workout.befit.repository.UserRepo.findByUsername(String)" because "this.userrepo" is null
        at com.workout.befit.services.CustomUserDetails.loadUserByUsername(CustomUserDetails.java:29) ~[classes/:na]
        at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:107) ~[spring-security-core-6.4.2.jar:6.4.2]

this is my repo

package com.workout.befit.repository;

import org.springframework.data.mongodb.repository.MongoRepository;

import com.workout.befit.models.User;
import java.util.Optional;


public interface UserRepo extends MongoRepository<User, String> {
    Optional<User> findByUsername(String username);
}

this is my security config

package com.workout.befit.utils;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.authentication.dao.DaoAuthenticationProvider;
import org.springframework.security.config.Customizer;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.SecurityFilterChain;

import com.workout.befit.services.CustomUserDetails;


@Configuration
@EnableWebSecurity
@ComponentScan
public class SecurityConfig {
    @Autowired
    @Qualifier("customuserdetails")
    CustomUserDetails customuserdetails;

    @Autowired
    PasswordEncoder passencoder;

    @Autowired
    AuthenticationProvider authprovider;
    

    @Bean
    public SecurityFilterChain securityFilterchain(HttpSecurity http) throws Exception {
        http
        .authorizeHttpRequests(authorize->authorize.requestMatchers("/signup","/about","/error/**").permitAll() //allow requests to signup page
        .anyRequest().authenticated()) //authenticate all other requests
        .httpBasic(Customizer.withDefaults())
        .formLogin(Customizer.withDefaults())
        .csrf(csrf-> csrf.disable());
        return http.build();
    }

    
 

}

this is my security bean

package com.workout.befit.utils;

import org.springframework.context.annotation.Bean;
import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.authentication.dao.DaoAuthenticationProvider;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.stereotype.Component;

import com.workout.befit.services.CustomUserDetails;

@Component
public class Securitybeans {
    @Bean
    public PasswordEncoder passwordEncoder() {
    return new BCryptPasswordEncoder();}

    @Bean
    public UserDetailsService customuserdetailsservice(){
        return new CustomUserDetails();
    }

    @Bean
    public AuthenticationProvider authprovider(){
        DaoAuthenticationProvider provider=new DaoAuthenticationProvider();
        provider.setPasswordEncoder(passwordEncoder());
        provider.setUserDetailsService(customuserdetailsservice());
        return provider;
    }
}

this is my custom user details service

package com.workout.befit.services;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Primary;
import org.springframework.security.core.userdetails.User.UserBuilder;
import org.springframework.security.crypto.password.PasswordEncoder;
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 com.workout.befit.models.User;
import com.workout.befit.repository.UserRepo;

@Service("customuserdetails")
public class CustomUserDetails implements UserDetailsService {

    @Autowired
    UserRepo userrepo;
    @Autowired
    PasswordEncoder bcrypt;


    @SuppressWarnings("null")
    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {   
        Optional<User> optionaluser=userrepo.findByUsername(username);
        User user=optionaluser.orElseThrow();
        UserBuilder builder = null;
        builder.username(user.getUsername());
        builder.password(bcrypt.encode(user.getPassword()));
        builder.authorities(user.getAuthorities());
        return builder.build();
    }

    
}

It says that this.userrepo in customuserdetailsservice is null therefore it can't call find by name function.

Try adding this in your code instead of using field level bean creation, use constructor based bean creation for the UserRepo in CustomerDetails class like mentioned by @M.Deinum

import lombok.RequiredArgsConstructor;

@Service("customuserdetails")
@RequiredArgsConstructor
public class CustomUserDetails implements UserDetailsService {

    private final UserRepo userrepo;
    private final PasswordEncoder bcrypt;
// rest of the code
}

and add the @Configuration annotation instead of @Component to SecurityBeans class

import org.springframework.context.annotation.Configuration;

@Configuration
public class Securitybeans {

    //rest of the code
}