Handle exception that is potentially occurred in WithdrawCoordinating

- Introduce a common parent class, AbstractFailed for IntentUpdate
  subclass representing failure
- Write Javadoc for each class representing failure

Change-Id: I3945642f5985ddd66c11b6de1924b9c1d23a5fc6
diff --git a/core/net/src/main/java/org/onosproject/net/intent/impl/WithdrawCoordinating.java b/core/net/src/main/java/org/onosproject/net/intent/impl/WithdrawCoordinating.java
index 2515a35..bd94ed6 100644
--- a/core/net/src/main/java/org/onosproject/net/intent/impl/WithdrawCoordinating.java
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/WithdrawCoordinating.java
@@ -17,6 +17,9 @@
 
 import org.onosproject.net.flow.FlowRuleOperations;
 import org.onosproject.net.intent.IntentData;
+import org.onosproject.net.intent.IntentException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Optional;
 
@@ -28,6 +31,8 @@
  */
 class WithdrawCoordinating implements IntentUpdate {
 
+    private static final Logger log = LoggerFactory.getLogger(WithdrawCoordinating.class);
+
     // TODO: define an interface and use it, instead of IntentManager
     private final IntentManager intentManager;
     private final IntentData pending;
@@ -41,8 +46,13 @@
 
     @Override
     public Optional<IntentUpdate> execute() {
-        FlowRuleOperations flowRules = intentManager.uninstallCoordinate(current, pending);
-        pending.setInstallables(current.installables());
-        return Optional.of(new Withdrawing(intentManager, pending, flowRules));
+        try {
+            FlowRuleOperations flowRules = intentManager.uninstallCoordinate(current, pending);
+            pending.setInstallables(current.installables());
+            return Optional.of(new Withdrawing(intentManager, pending, flowRules));
+        } catch (IntentException e) {
+            log.warn("Unable to generate generate a FlowRuleOperations from intent {} due to:", pending.intent(), e);
+            return Optional.of(new WithdrawingFailed(pending));
+        }
     }
 }