Token is generating as null for login using springboot

I would like to generate the token for login using springboot, The token is generating while checking using postman, but I am getting null in console

Authenticate controller

package com.demo.grocery.controller;

import com.demo.grocery.config.JwtUtils;
import com.demo.grocery.model.JwtRequest;
import com.demo.grocery.model.JwtResponse;
import com.demo.grocery.model.User;
import com.demo.grocery.service.impl.UserDetailsServiceImpl;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.DisabledException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.web.bind.annotation.*;

import java.security.Principal;

@RestController
public class AuthenticateController {
    @Autowired
    private AuthenticationManager authenticationManager;

    @Autowired
    private UserDetailsServiceImpl userDetailsServiceImpl;

    @Autowired
    private JwtUtils jwtUtils;

    //generate token
    @CrossOrigin("http://localhost:4200")
    @PostMapping("/generate-token")
    public ResponseEntity<?> generateToken(@RequestBody JwtRequest jwtRequest) throws Exception
    {

        try {

            this.authenticate(jwtRequest.getUsername(), jwtRequest.getPassword());

        } catch (UsernameNotFoundException e) {
            // TODO: handle exception
            e.printStackTrace();
            throw new Exception("User Not Found");
        }

        ////////////authenticate
        UserDetails userDetails =  this.userDetailsServiceImpl.loadUserByUsername(jwtRequest.getUsername());

        String token = this.jwtUtils.generateToken(userDetails);

        return ResponseEntity.ok(new JwtResponse(token));

    }

    private void authenticate(String username, String password) throws Exception
    {
        try {

            authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(username, password));

        } catch (DisabledException e) {

            e.printStackTrace();
            throw new Exception("USER DISABLED "+e.getMessage());
        }

        catch(BadCredentialsException e)
        {
            throw new Exception("Invalid Credentials "+e.getMessage());
        }
    }

    //returns the details of current logged in user
    @CrossOrigin("http://localhost:4200")
    @GetMapping("/current-user")
    public User getCurrentUser(Principal principal)
    {
        return (User) this.userDetailsServiceImpl.loadUserByUsername(principal.getName());


    }
}

JwtAuthenticationFilter

package com.demo.grocery.config;

import com.demo.grocery.service.impl.UserDetailsServiceImpl;

import io.jsonwebtoken.ExpiredJwtException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.web.authentication.WebAuthenticationDetailsSource;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Component
public class JwtAuthenticationFilter extends OncePerRequestFilter {

    @Autowired
    private UserDetailsServiceImpl userDetailsService;

    @Autowired
    private JwtUtils jwtUtil;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        final String requestTokenHeader = request.getHeader("Authorization");

        System.out.println(requestTokenHeader);

        String username = null;
        String jwtToken = null;

        if (requestTokenHeader != null && requestTokenHeader.startsWith("Bearer ")) {
            // yes

            jwtToken = requestTokenHeader.substring(7);
            try {

                username = this.jwtUtil.extractUsername(jwtToken);

            } catch (ExpiredJwtException e) {

                e.printStackTrace();
                System.out.println("jwt token has expired..");
            }

            catch (Exception e) {

                e.printStackTrace();
                System.out.println("error");
            }

        }

        else {
            System.out.println("Invalid Token, Not Starts with bearer String");
        }

        //validate Token
        if(username!=null && SecurityContextHolder.getContext().getAuthentication() == null)
        {
            final UserDetails userDetails = this.userDetailsService.loadUserByUsername(username);

            if(this.jwtUtil.validateToken(jwtToken, userDetails))
            {
                //token is valid
                UsernamePasswordAuthenticationToken usernamePasswordAuthentication = new UsernamePasswordAuthenticationToken(userDetails,null,userDetails.getAuthorities());
                usernamePasswordAuthentication.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));

                SecurityContextHolder.getContext().setAuthentication(usernamePasswordAuthentication);

            }
            else
            {
                System.out.println("Token is not Valid");
            }
        }

        filterChain.doFilter(request, response);
    }

}

Service

package com.demo.grocery.service.impl;

import com.demo.grocery.model.User;
import com.demo.grocery.repository.UserRepo;

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;

@Service
public class UserDetailsServiceImpl implements UserDetailsService {

    @Autowired
    private UserRepo userRepository;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        User user = this.userRepository.findByUsername(username);

        if (user == null) {
            System.out.println("User Not Found");
            throw new UsernameNotFoundException("No User Found!!");
        }
        return user;
    }

}

Output in intelliji

Postman output

Look into the screenshots and help me to solve the issue. Why it is storing as null?