public class CustomAuthenticationFailureHandler 
 implements AuthenticationFailureHandler {
 
  private ObjectMapper objectMapper = new ObjectMapper();
 
  @Override
  public void onAuthenticationFailure(
   HttpServletRequest request,
   HttpServletResponse response,
   AuthenticationException exception) 
   throws IOException, ServletException {
 
    response.setStatus(HttpStatus.UNAUTHORIZED.value());
    Map data = new HashMap<>();
    data.put(
     "timestamp", 
     Calendar.getInstance().getTime());
    data.put(
     "exception", 
     exception.getMessage());
 
    response.getOutputStream()
     .println(objectMapper.writeValueAsString(data));
  }
}

@Configuration
@EnableWebSecurity
public class SecurityConfiguration 
 extends WebSecurityConfigurerAdapter {
 
  @Override
  protected void configure(AuthenticationManagerBuilder auth) 
   throws Exception {
    auth
     .inMemoryAuthentication()
     .withUser("baeldung")
     .password("baeldung")
     .roles("USER");
  }
 
  @Override
  protected void configure(HttpSecurity http) 
   throws Exception {
    http
     .authorizeRequests()
     .anyRequest()
     .authenticated()
     .and()
     .formLogin()
     .failureHandler(customAuthenticationFailureHandler());
  }
 
  @Bean
  public AuthenticationFailureHandler customAuthenticationFailureHandler() {
    return new CustomAuthenticationFailureHandler();
  }
}