清空提供者

git-svn-id: http://code.alibabatech.com/svn/dubbo/trunk@1547 1a56cb94-b969-4eaa-88fa-be21384802f2

dubbo-registry/dubbo-registry-api/src/main/java/com/alibaba/dubbo/registry/integration/RegistryDirectory.java

@@ -339,12 +339,15 @@ public class RegistryDirectory<T> extends AbstractDirectory<T> implements Notify
      * @return invokers
      */
     private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
+        Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<String, Invoker<T>>();
         if(urls == null || urls.size() == 0){
-            return null;
+            return newUrlInvokerMap;
         }
-        Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<String, Invoker<T>>();
         Set<String> keys = new HashSet<String>();
         for (URL providerUrl : urls) {
+            if (Constants.EMPTY_PROTOCOL.equals(providerUrl.getProtocol())) {
+                continue;
+            }
             URL url = mergeUrl(providerUrl);
             
             String key = url.toFullString(); // URL参数是排序的