springboot for backend reactjs frontend - reactjs

Question

i use springboot and reactjs everthing was working before adding security to backend, now as go to web page to retrieve my data, i do not see any data there. I go to console it says the username not defined:do not know what does it mean.
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8080/users/undefined/todos. (Reason: CORS request did not succeed)
UPDATE: I tried to both code but did not help.
does this mean anything serious:
"Uncaught (in promise) Error: Network Error
at createError" (createError.js:16)
Access to XMLHttpRequest at 'http://localhost:8080/users/undefined/todos' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
xhr.js:177 GET http://localhost:8080/users/undefined/todos net::ERR_FAILED
dispatchXhrRequest # xhr.js:177
xhrAdapter # xhr.js:13
todos:1 Access to XMLHttpRequest at 'http://localhost:8080/users/undefined/todos' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
xhr.js:177 GET http://localhost:8080/users/undefined/todos net::ERR_FAILED
dispatchXhrRequest # xhr.js:177
xhrAdapter # xhr.js:13
dispatchRequest # dispatchRequest.js:52
createError.js:16 Uncaught (in promise) Error: Network Error
at createError (createError.js:16)

Answer 1

Add #CrossOrigin(origins = "http://localhost:3000") (if you run your client at 3000), or use this bean (in SecurityConfig):
#Bean
public CorsConfigurationSource corsConfigurationSource() {
final CorsConfiguration configuration = new CorsConfiguration();
configuration.setAllowedOrigins(Arrays.asList("http://localhost:3000"));
configuration.setAllowedMethods(Arrays.asList("GET", "POST", "OPTIONS"));
configuration.setAllowCredentials(true);
configuration.setAllowedHeaders(Arrays.asList("*"));
configuration.setExposedHeaders(Arrays.asList("x-auth-token", "xsrf-token"));
final UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
source.registerCorsConfiguration("/**", configuration);
return source;
}