if the problem that from the frontend endpoint and port you can't get any result or data from tha backend then as i think there's a solution for this by adding this code to your backendApplication file |-- Application | |-- controller | |-- Entity | |-- DTO | |-- BackendApplication.jav here is the code =>

@Bean
  public CorsFilter corsFilter() {
      CorsConfiguration corsConfiguration = new CorsConfiguration();
      corsConfiguration.setAllowCredentials(true);
      corsConfiguration.setAllowedOrigins(Arrays.asList("http://localhost:4200"));
      corsConfiguration.setAllowedHeaders(Arrays.asList("Origin", "Access-Control-Allow-Origin", "Content-Type",
            "Accept", "Authorization", "Origin, Accept", "X-Requested-With",
            "Access-Control-Request-Method", "Access-Control-Request-Headers"));
      corsConfiguration.setExposedHeaders(Arrays.asList("Origin", "Content-Type", "Accept", "Authorization",
            "Access-Control-Allow-Origin", "Access-Control-Allow-Origin", "Access-Control-Allow-Credentials"));
      corsConfiguration.setAllowedMethods(Arrays.asList("GET", "POST", "PUT", "DELETE", "OPTIONS"));
      UrlBasedCorsConfigurationSource urlBasedCorsConfigurationSource = new UrlBasedCorsConfigurationSource();
      urlBasedCorsConfigurationSource.registerCorsConfiguration("/**", corsConfiguration);
      return new CorsFilter(urlBasedCorsConfigurationSource);
  }

don't forgot this annotation @Bean