[RESTEASY-2541] Fix RestClientListeners

resteasy-client-microprofile/src/main/java/org/jboss/resteasy/microprofile/client/RestClientListeners.java

@@ -5,30 +5,34 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.List;
+import java.util.Map;
 import java.util.ServiceLoader;
-
-
-public class RestClientListeners {
-
-    private RestClientListeners() {
-    }
-
-    private static final Collection<RestClientListener> listeners;
-
-    static {
-        listeners = loadListeners();
-    }
-
-    private static List<RestClientListener> loadListeners() {
-        List<RestClientListener> listeners = new ArrayList<>();
-        ServiceLoader.load(RestClientListener.class)
-                .forEach(listeners::add);
-        Collections.unmodifiableCollection(listeners);
-        return listeners;
-    }
-
-    public static Collection<RestClientListener> get() {
-        return listeners;
-    }
+import java.util.WeakHashMap;
+
+public class RestClientListeners
+{
+
+   private RestClientListeners()
+   {
+   }
+
+   /**
+    * A synchronized weak hash map that keeps RestClientListener instances retrieved using ServiceLoader for each classloader.
+    * Weak keys are used to remove entries when classloaders are garbage collected.
+    */
+   private static Map<ClassLoader, Collection<RestClientListener>> map = Collections
+         .synchronizedMap(new WeakHashMap<ClassLoader, Collection<RestClientListener>>());
+
+   public static Collection<RestClientListener> get()
+   {
+      ClassLoader loader = Thread.currentThread().getContextClassLoader();
+      Collection<RestClientListener> c;
+      c = map.get(loader);
+      if (c == null) {
+         c = new ArrayList<>();
+         ServiceLoader.load(RestClientListener.class, loader).forEach(c::add);
+         map.put(loader, Collections.unmodifiableCollection(c));
+      }
+      return c;
+   }
 }