org.argeo.util/src/org/argeo/util/register/Singleton.java

   1 package org.argeo.util.register;
   2
   3 import java.util.ArrayList;
   4 import java.util.List;
   5 import java.util.concurrent.CompletableFuture;
   6 import java.util.concurrent.CompletionStage;
   7 import java.util.concurrent.Future;
   8 import java.util.function.Consumer;
   9
  10 public class Singleton<T> {
  11         private final Class<T> clss;
  12         private final CompletableFuture<T> registrationStage;
  13         private final List<Consumer<T>> unregistrationHooks = new ArrayList<>();
  14
  15         public Singleton(Class<T> clss, CompletableFuture<T> registrationStage) {
  16                 this.clss = clss;
  17                 this.registrationStage = registrationStage;
  18         }
  19
  20         CompletionStage<T> getRegistrationStage() {
  21                 return registrationStage.minimalCompletionStage();
  22         }
  23
  24         public void addUnregistrationHook(Consumer<T> todo) {
  25                 unregistrationHooks.add(todo);
  26         }
  27
  28         public Future<T> getValue() {
  29                 return registrationStage.copy();
  30         }
  31
  32         public CompletableFuture<Void> prepareUnregistration(Void v) {
  33                 List<CompletableFuture<Void>> lst = new ArrayList<>();
  34                 for (Consumer<T> hook : unregistrationHooks) {
  35                         lst.add(registrationStage.thenAcceptAsync(hook));
  36                 }
  37                 CompletableFuture<Void> prepareUnregistrationStage = CompletableFuture
  38                                 .allOf(lst.toArray(new CompletableFuture<?>[lst.size()]));
  39                 return prepareUnregistrationStage;
  40         }
  41 }