Issue #1 : providing a way to shutdown executor services.

src/main/java/com/github/fge/msgsimple/provider/LoadingMessageSourceProvider.java

@@ -29,16 +29,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.concurrent.Callable;
-import java.util.concurrent.CancellationException;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.FutureTask;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ThreadFactory;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
+import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
@@ -89,6 +80,7 @@ public final class LoadingMessageSourceProvider
         public Thread newThread(final Runnable r)
         {
             final Thread ret = factory.newThread(r);
+            ret.setName(LoadingMessageSourceProvider.class.getSimpleName());
             ret.setDaemon(true);
             return ret;
         }
@@ -97,12 +89,17 @@ public Thread newThread(final Runnable r)
     private static final InternalBundle BUNDLE = InternalBundle.getInstance();
 
     private static final int NTHREADS = 3;
+
+    //We need a central place to put executors so we can shut them all down on request
+    private static final CopyOnWriteArrayList<ExecutorService> executors = new CopyOnWriteArrayList<ExecutorService>();
+
+    //Need to track if we're shutdown or not.
+    private static final AtomicBoolean shutdown = new AtomicBoolean(false);
 
     /*
      * Executor service for loading tasks
      */
-    private final ExecutorService service
-        = Executors.newFixedThreadPool(NTHREADS, THREAD_FACTORY);
+    private ExecutorService service = Executors.newFixedThreadPool(NTHREADS, THREAD_FACTORY);
 
     /*
      * Loader and default source
@@ -146,6 +143,8 @@ private LoadingMessageSourceProvider(final Builder builder)
          * Mimic an already enabled expiry if, in fact, there is none
          */
         expiryEnabled = new AtomicBoolean(expiryDuration == 0L);
+
+        executors.addIfAbsent(service);
     }
 
     /**
@@ -158,9 +157,43 @@ public static Builder newBuilder()
         return new Builder();
     }
 
+    /**
+     * Shuts down all current ExecutorServices by calling shutdownNow() on each of them.
+     * This is handy for clients that need to explicitly destroy executors/threads before the jvm is terminated.
+     * 
+     * For example, in an OSGi application, you may need to stop a bundle using this and start it up again later without
+     * a JVM restart. Without a way to shutdown the executors, it could lead to OOMEs.
+     */
+    public static void shutdown()
+    {
+        for(ExecutorService e : executors)
+        {
+            e.shutdownNow();
+        }
+
+        shutdown.set(true);
+    }
+
+    /**
+     * Restarts all ExecutorServices that have been shutdown
+     */
+    public static void restartIfNeeded()
+    {
+        if(shutdown.get())
+        {
+            shutdown.set(false);
+        }
+    }
+
     @Override
     public MessageSource getMessageSource(final Locale locale)
     {
+        if(shutdown.get())
+        {
+            return defaultSource;
+        }
+
+        ensureServiceIsReady();
         /*
          * Set up expiry, if necessary
          */
@@ -236,6 +269,18 @@ public MessageSource getMessageSource(final Locale locale)
         }
     }
 
+    private void ensureServiceIsReady()
+    {
+        if(null == service || service.isShutdown() || service.isTerminated())
+        {
+            executors.remove(service);
+
+            service = Executors.newFixedThreadPool(NTHREADS, THREAD_FACTORY);
+
+            executors.addIfAbsent(service);
+        }
+    }
+
     private FutureTask<MessageSource> loadingTask(final Locale locale)
     {
         return new FutureTask<MessageSource>(new Callable<MessageSource>()