<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
<groupId>io.jsonwebtoken</groupId>
<artifactId>jjwt</artifactId>
<version>0.9.1</version>
</dependency>

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

@Component
public class JwtTokenUtil {
    private static final long JWT_TOKEN_VALIDITY = 5 * 60 * 60;
    @Value("${jwt.secret}")
    private String secret;

    public String generateToken(UserDetails userDetails) {
        Map<String, Object> claims = newHashMap <>();
        return createToken(claims, userDetails.getUsername());
    }
    private String createToken(Map<String, Object> claims, String subject) {
        Date now = new Date();
        Date expiration = new Date(now.getTime() + JWT_TOKEN_VALIDITY * 1000);
        return Jwts.builder()
                .setClaims(claims)
                .setSubject(subject)
                .setIssuedAt(now)
                .setExpiration(expiration)
                .signWith(SignatureAlgorithm.HS256, secret)
                .compact();
    }
    public boolean validateToken(String token, UserDetails userDetails) {
        final String username = extractUsername(token);
        return (username.equals(userDetails.getUsername()) && !isTokenExpired(token));
    }
    private boolean isTokenExpired(String token) {
        return extractExpiration(token).before(new Date());
    }
    public String extractUsername(String token) {
        return extractClaim(token, Claims::getSubject);
    }
    public Date extractExpiration(String token) {
        return extractClaim(token, Claims::getExpiration);
    }
    private <T> T extractClaim(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = extractAllClaims(token);
        return claimsResolver.apply(claims);
    }
    private Claims extractAllClaims(String token) {
        return Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
    }
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.userdetails.User;
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 JwtUserDetailsService implements UserDetailsService {
    @Autowired
    private UserRepository userRepository;
    @Override
    public UserDetails loadUserByUsername(String username)
            throws UsernameNotFoundException {
        UserEntity user = userRepository.findByUsername(username);
        if (user == null) {
            throw new UsernameNotFoundException("User not found with username: " + username);
        }
        return new User(user.getUsername(), user.getPassword(),
                new ArrayList<>());
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

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

public class JwtAuthenticationFilter extends UsernamePasswordAuthenticationFilter {
    private final AuthenticationManager authenticationManager;
    private final JwtTokenUtil jwtTokenUtil;

    public JwtAuthenticationFilter(AuthenticationManager authenticationManager, JwtTokenUtil jwtTokenUtil) {
        this.authenticationManager = authenticationManager;
        this.jwtTokenUtil = jwtTokenUtil;
    }

    @Override
    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        try {
            LoginRequest loginRequest = new ObjectMapper().readValue(request.getInputStr eam(), LoginRequest.class);
            return authenticationManager.authenticate(
                    new UsernamePasswordAuthenticationToken(loginRequest.getUsername(), loginRequest.getPassword(), Collections.emptyList())
            );
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    protected void successfulAuthentication(HttpServletRequest request, HttpServletResponse response, FilterChain chain, Authentication authResult)throwsIOException,ServletException {
        UserDetails userDetails = (UserDetails) authResult.getPrincipal();
        String token = jwtTokenUtil.generateToken(userDetails);
        response.addHeader("Authorization", "Bearer " + token);
    }

    private static class LoginRequest {
        private String username;
        private String password;

        public String getUsername() {
            return username;
        }

        public void setUsername(String username) {
            this.username = username;
        }

        public String getPassword() {
            return password;
        }

        public void setPassword(String password) {
            this.password = password;
        }
    }
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Autowired
    private JwtUserDetailsService jwtUserDetailsService;
    @Autowired
    private JwtAuthenticationEntryPoint jwtAuthenticationEntryPoint;
    @Autowired
    private JwtTokenUtil jwtTokenUtil;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable()
                .authorizeRequests().antMatchers("/authenticate").permitAll()
                .anyRequest().authenticated().and()
                .exceptionHandling().authenticationEntryPoint(jwtAuthenticationEntryPoint).and()
                .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS);
        http.addFilterBefore(newJwtAuthenticationFilter(authenticationManager(), jwtTokenUtil), UsernamePasswordAuthenticationFilter.class);
    }
    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(jwtUserDetailsService).passwordEncoder(passwordEncoder());
    }
    @Override
    @Bean
    public AuthenticationManager authenticationManagerBean() throws Exception {
        return super.authenticationManagerBean();
    }
    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }
}

bash
curl -X POST \
  http://localhost:8080/authenticate \
  -H 'Content-Type: application/json'\
  -d '{
    "username": "user",
    "password": "password"
}'

bash
curl -X GET \
  http://localhost:8080/hello \
  -H 'Authorization: Bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyIiwiaWF0IjoxNjI0MDM2NzA4LCJleHAiOjE2MjQwMzc1MDh9.9fZS7jPp0NzB0JyOo4y4jO4x3s3KjV7yW1nLzV7cO_c'