Fix FindBugs error in DelayedListenerRegistration#getInstance

The ObjectRegistration interface was recently changed to annotate
getInstance with @Nonnull to promise it will not return a null.
However DelayedListenerRegistration could return null if the delegate
is not set yet. In reality, we do not and should not ever call this
method on DelayedListenerRegistration instances so I changed it to
throw UnsupportedOperationException to make it explicit and to avoid
the FindBugs error.

Change-Id: I9fe374b23336d8ade65b2f1b697d93f50a090df9
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>

diff --git a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/DelayedListenerRegistration.java b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/DelayedListenerRegistration.java
index ac132721c5dcc9954a152f0fcc5d1a94787e0fe5..8d73bc6155d2c664ba6448a1085bbf85850d9606 100644 (file)
--- a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/DelayedListenerRegistration.java
+++ b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/DelayedListenerRegistration.java
@@ -39,8 +39,13 @@ abstract class DelayedListenerRegistration<L extends EventListener, M> implement
 
     @Override
     public L getInstance() {
 
     @Override
     public L getInstance() {

-        final ListenerRegistration<L> d = delegate;
-        return d == null ? null : (L)d.getInstance();
+        // ObjectRegistration annotates this method as @Nonnull but we could return null if the delegate is not set yet.
+        // In reality, we do not and should not ever call this method on DelayedListenerRegistration instances anyway
+        // but, since we have to provide an implementation to satisfy the interface, we throw
+        // UnsupportedOperationException to honor the API contract of not returning null and to avoid a FindBugs error
+        // for possibly returning null.
+        throw new UnsupportedOperationException(
+                "getInstance should not be called on this instance since it could be null");

     }
 
     @Override
     }
 
     @Override