1. import java.util.HashMap;
  2. import java.util.Map;
  3. import java.util.concurrent.Executors;
  4. import java.util.concurrent.ScheduledExecutorService;
  5. import java.util.concurrent.TimeUnit;
  7. public class EnvVariableFilter {
  9. private final Map<String, String> filteredEnvVars = new HashMap<>();
  10. private final String[] variablesToFilter;
  11. private final long retryIntervalMillis;
  12. private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
  14. public EnvVariableFilter(String[] variablesToFilter, long retryIntervalMillis) {
  15. this.variablesToFilter = variablesToFilter;
  16. this.retryIntervalMillis = retryIntervalMillis;
  17. }
  19. public void initialize() {
  20. for (String var : variablesToFilter) {
  21. try {
  22. String value = System.getenv(var);
  23. if (value != null && !value.isEmpty()) {
  24. filteredEnvVars.put(var, value);
  25. }
  26. } catch (NullPointerException e) {
  27. // Handle potential null pointer exceptions
  28. System.err.println("Variable " + var + " not found.");
  29. }
  30. }
  31. startRetryScheduler();
  32. }
  35. private void startRetryScheduler() {
  36. for (String var : variablesToFilter) {
  37. scheduler.scheduleAtFixedRate(() -> {
  38. try {
  39. String value = System.getenv(var);
  40. if (value != null && !value.isEmpty()) {
  41. filteredEnvVars.put(var, value);
  42. } else {
  43. System.err.println("Variable " + var + " not found (retry).");
  44. }
  45. } catch (NullPointerException e) {
  46. System.err.println("Variable " + var + " not found (retry).");
  47. }
  48. }, retryIntervalMillis, retryIntervalMillis, TimeUnit.MILLISECONDS);
  49. }
  50. }
  52. public Map<String, String> getFilteredEnvVars() {
  53. return new HashMap<>(filteredEnvVars); // Return a copy to prevent external modification
  54. }
  56. public void stop() {
  57. scheduler.shutdown();
  58. try {
  59. scheduler.awaitTermination(5, TimeUnit.SECONDS); // Give tasks time to finish
  60. } catch (InterruptedException e) {
  61. System.err.println("Scheduler termination interrupted.");
  62. }
  63. }
  66. public static void main(String[] args) {
  67. String[] variables = {"MY_API_KEY", "DATABASE_URL", "DEBUG"};
  68. long interval = 2000; // Retry every 2 seconds
  70. EnvVariableFilter filter = new EnvVariableFilter(variables, interval);
  71. filter.initialize();
  73. // Keep the program running for a while to allow retries
  74. try {
  75. Thread.sleep(10000);
  76. } catch (InterruptedException e) {
  77. e.printStackTrace();
  78. }
  79. filter.stop();
  81. Map<String, String> filteredVars = filter.getFilteredEnvVars();
  82. System.out.println(filteredVars);
  83. }
  84. }

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