spring security fail authentication

Question

I am a beginner with spring boot I want to implement authentication using spring security but when I send a request with postman to authenticate the authentication fails I did a debug and I see that the variable username and password equal a null I think that's the reason, I want to know why these 2 variables equal to null? can you help me

@Configuration
@EnableConfigurationProperties
@EnableWebSecurity

public class SecurityConfiguration extends WebSecurityConfigurerAdapter{
    
    @Autowired
    UsersService userService;
    @Autowired
    PasswordEncoder passwordEncoder;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        // TODO Auto-generated method stub
        http.cors().and().csrf().disable() 
             .authorizeRequests()
            .antMatchers(HttpMethod.POST,"/add-users").permitAll()
            .anyRequest()
            .authenticated()
            .and()
            .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS) 
            .and()
            .addFilter(new AuthenticationFilter(authenticationManagerBean(), userService));
           
    }
    
    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        // TODO Auto-generated method stub
        auth.userDetailsService(userService)
            .passwordEncoder(passwordEncoder()); 
    }
    
    @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception {
        // TODO Auto-generated method stub
        return super.authenticationManagerBean();
    }
    
    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder(); 
    }

public class AuthenticationFilter extends UsernamePasswordAuthenticationFilter{
    
    private String secretKey = "lpmppm";
    private final AuthenticationManager authManager;
    private final UsersService userservice;
    
    public AuthenticationFilter(AuthenticationManager authManager, UsersService userservice) {
        super();
        this.authManager = authManager;
        this.userservice = userservice;
    }
    
    @Override
    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response)
            throws AuthenticationException {
        // TODO Auto-generated method stub
        
        String username=request.getParameter("username");
        String password = request.getParameter("password");
        
        UsernamePasswordAuthenticationToken authToken=new UsernamePasswordAuthenticationToken(username, password);
        return authManager.authenticate(authToken);
    }
    
    @Override
    protected void successfulAuthentication(HttpServletRequest request, HttpServletResponse response, FilterChain chain,
            Authentication authResult) throws IOException, ServletException {
        // TODO Auto-generated method stub
    //  super.successfulAuthentication(request, response, chain, authResult);
        String token= Jwts.builder()
                .setSubject(authResult.getName())
                .claim("authorites", authResult.getAuthorities())
                .setIssuedAt(new Date())
                .setExpiration(java.sql.Date.valueOf(LocalDate.now().plusDays(3)))
                .signWith(Keys.hmacShaKeyFor(secretKey.getBytes()))
                .compact();
        
        response.addHeader("Authorization","Bearer" + token);
    }