1. import java.util.HashMap;
  2. import java.util.Map;
  4. public class TokenFlattener {
  6. /**
  7. * Flattens a nested authentication token structure into a single-level map.
  8. * Handles potential null values gracefully.
  9. *
  10. * @param token The nested token structure (Map).
  11. * @return A flattened map containing the token data, or an empty map if input is null.
  12. */
  13. public static Map<String, String> flattenToken(Map<?, ?> token) {
  14. Map<String, String> flattenedToken = new HashMap<>();
  16. if (token == null) {
  17. return flattenedToken; // Handle null input gracefully
  18. }
  20. flattenHelper(token, "", flattenedToken);
  21. return flattenedToken;
  22. }
  24. private static void flattenHelper(Map<?, ?> token, String prefix, Map<String, String> flattenedToken) {
  25. for (Map.Entry<?, ?> entry : token.entrySet()) {
  26. String key = String.valueOf(entry.getKey()); // Convert key to string
  27. String value = String.valueOf(entry.getValue()); // Convert value to string
  29. String newKey = prefix.isEmpty() ? key : prefix + "." + key;
  31. if (value == null) {
  32. flattenedToken.put(newKey, null); // Handle null values
  33. } else {
  34. flattenedToken.put(newKey, value);
  35. }
  37. if (entry.getValue() instanceof Map) {
  38. flattenHelper((Map<?, ?>) entry.getValue(), newKey, flattenedToken); // Recursive call for nested maps
  39. }
  40. }
  41. }
  43. public static void main(String[] args) {
  44. // Example usage:
  45. Map<String, Object> nestedToken = new HashMap<>();
  46. nestedToken.put("username", "testuser");
  47. nestedToken.put("details", new HashMap<>());
  48. Map<String, Object> details = new HashMap<>();
  49. details.put("email", "test@example.com");
  50. details.put("role", "user");
  51. nestedToken.put("permissions", new HashMap<>());
  53. Map<String, String> flattened = flattenToken(nestedToken);
  54. System.out.println(flattened);
  55. }
  56. }

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