Close async tasks properly when shutting down

Common/src/main/java/net/frankheijden/serverutils/common/managers/AbstractTaskManager.java

@@ -12,7 +12,7 @@ public abstract class AbstractTaskManager<T> {
 
     private final List<T> serverTasks;
     private final Consumer<T> taskCloser;
-    private final Map<String, AbstractTask> tasks;
+    private final Map<String, RunningTask> tasks;
 
     /**
      * Constructs a new TaskManager with a consumer which closes a task.
@@ -24,31 +24,56 @@ public abstract class AbstractTaskManager<T> {
         this.tasks = new HashMap<>();
     }
 
-    public abstract void runTask(Runnable runnable);
+    protected abstract T runTaskImpl(Runnable runnable);
 
-    public void runTask(String key, AbstractTask task) {
-        tasks.put(key, task);
-        runTask(task);
+    public T runTask(Runnable runnable) {
+        return addTask(runTaskImpl(runnable));
     }
 
-    public abstract void runTaskAsynchronously(Runnable runnable);
-
-    public void runTaskAsynchronously(String key, AbstractTask task) {
-        tasks.put(key, task);
-        runTaskAsynchronously(task);
+    /**
+     * Associates a synchronous task with a key which can be cancelled later by that key.
+     * @param key The key of the task.
+     * @param abstractTask The AbstractTask.
+     * @return The implementation-specific scheduled task.
+     */
+    public T runTask(String key, AbstractTask abstractTask) {
+        T task = runTask(abstractTask);
+        tasks.put(key, new RunningTask(task, abstractTask));
+        return task;
     }
 
-    public void addTask(T task) {
+    protected abstract T runTaskAsynchronouslyImpl(Runnable runnable);
+
+    public T runTaskAsynchronously(Runnable runnable) {
+        return addTask(runTaskAsynchronouslyImpl(runnable));
+    }
+
+    /**
+     * Associates an asynchronous task with a key which can be cancelled later by that key.
+     * @param key The key of the task.
+     * @param abstractTask The AbstractTask.
+     * @return The implementation-specific scheduled task.
+     */
+    public T runTaskAsynchronously(String key, AbstractTask abstractTask) {
+        T task = runTaskAsynchronously(abstractTask);
+        tasks.put(key, new RunningTask(task, abstractTask));
+        return task;
+    }
+
+    private T addTask(T task) {
         serverTasks.add(task);
+        return task;
     }
 
+    public abstract void cancelTask(T task);
+
     /**
      * Cancels a single task by key.
      * @param key The key of the task.
      * @return Whether or not the task existed.
      */
     public boolean cancelTask(String key) {
-        AbstractTask task = tasks.remove(key);
+        RunningTask task = tasks.remove(key);
         if (task == null) return false;
         task.cancel();
         return true;
@@ -58,7 +83,7 @@ public abstract class AbstractTaskManager<T> {
      * Cancels all tasks.
      */
     public void cancelAllTasks() {
-        for (AbstractTask task : tasks.values()) {
+        for (RunningTask task : tasks.values()) {
             task.cancel();
         }
         tasks.clear();
@@ -68,4 +93,19 @@ public abstract class AbstractTaskManager<T> {
         }
         serverTasks.clear();
     }
+
+    private final class RunningTask {
+        private final T task;
+        private final AbstractTask abstractTask;
+
+        private RunningTask(T task, AbstractTask abstractTask) {
+            this.task = task;
+            this.abstractTask = abstractTask;
+        }
+
+        public void cancel() {
+            cancelTask(task);
+            abstractTask.cancel();
+        }
+    }
 }

Common/src/main/java/net/frankheijden/serverutils/common/tasks/PluginWatcherTask.java

@@ -4,6 +4,7 @@ import com.sun.nio.file.SensitivityWatchEventModifier;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.ClosedWatchServiceException;
 import java.nio.file.FileSystems;
 import java.nio.file.StandardWatchEventKinds;
 import java.nio.file.WatchEvent;
@@ -41,6 +42,8 @@ public class PluginWatcherTask extends AbstractTask {
     private File file;
     private final AtomicBoolean run;
 
+    private WatchService watchService;
+
     /**
      * Constructs a new PluginWatcherTask for the specified plugin.
      * @param pluginName The name of the plugin.
@@ -55,6 +58,8 @@ public class PluginWatcherTask extends AbstractTask {
     @Override
     public void run() {
         try (WatchService watchService = FileSystems.getDefault().newWatchService()) {
+            this.watchService = watchService;
+
             File folder = pluginManager.getPluginsFolder();
             folder.toPath().register(watchService, EVENTS, SensitivityWatchEventModifier.HIGH);
 
@@ -76,9 +81,9 @@ public class PluginWatcherTask extends AbstractTask {
                     break;
                 }
             }
-        } catch (IOException ex) {
+        } catch (IOException | InterruptedException ex) {
             ex.printStackTrace();
-        } catch (InterruptedException ignored) {
+        } catch (ClosedWatchServiceException ignored) {
             //
         }
     }
@@ -93,5 +98,10 @@ public class PluginWatcherTask extends AbstractTask {
     @Override
     public void cancel() {
         run.set(false);
+        try {
+            watchService.close();
+        } catch (IOException ex) {
+            ex.printStackTrace();
+        }
     }
 }