diff --git a/src/main/java/net/onrc/onos/api/flowmanager/Flow.java b/src/main/java/net/onrc/onos/api/flowmanager/Flow.java
index 8608adb..65dc00e 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/Flow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/Flow.java
@@ -5,10 +5,11 @@
 import java.util.List;
 
 import net.onrc.onos.api.batchoperation.BatchOperationTarget;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.match.Match;
+import net.onrc.onos.core.util.IdGenerator;
 
 /**
  * An abstract class to define flow object which is managed by
@@ -67,8 +68,8 @@
      */
     public abstract List<MatchActionOperations> compile(
             FlowBatchOperation.Operator op,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator);
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator);
 
     /**
      * Generates a hash code using the FlowId.
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/FlowId.java b/src/main/java/net/onrc/onos/api/flowmanager/FlowId.java
index 3e94c7b..3bf9a30 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/FlowId.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/FlowId.java
@@ -26,7 +26,8 @@
     /**
      * Creates new instance with string ID.
      * <p>
-     * This FlowId instance should be generated with {@link FlowIdGenerator}.
+     * This FlowId instance should be generated with
+     * {@link net.onrc.onos.core.util.IdGenerator} of flow ID.
      *
      * @param id String representation of the ID.
      */
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java b/src/main/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java
deleted file mode 100644
index 9b85e22..0000000
--- a/src/main/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package net.onrc.onos.api.flowmanager;
-
-/**
- * An generator of {@link FlowId}.
- */
-public interface FlowIdGenerator {
-    /**
-     * Generates a global unique {@link FlowId} instance.
-     *
-     * @return a global unique {@link FlowId} instance.
-     */
-    FlowId getNewId();
-}
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/FlowManagerService.java b/src/main/java/net/onrc/onos/api/flowmanager/FlowManagerService.java
index 93a4e6c..4c19cbd 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/FlowManagerService.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/FlowManagerService.java
@@ -1,5 +1,7 @@
 package net.onrc.onos.api.flowmanager;
 
+import net.onrc.onos.core.util.IdGenerator;
+
 import java.util.Collection;
 
 /**
@@ -65,7 +67,7 @@
      * Gets ID generator for Flow objects.
      * @return the ID generator for Flow objects
      */
-    FlowIdGenerator getFlowIdGenerator();
+    IdGenerator<FlowId> getFlowIdGenerator();
 
     /**
      * Sets a conflict detection policy.
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/OpticalPathFlow.java b/src/main/java/net/onrc/onos/api/flowmanager/OpticalPathFlow.java
index 51dce43..a352f05 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/OpticalPathFlow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/OpticalPathFlow.java
@@ -3,12 +3,13 @@
 import java.util.List;
 
 import net.onrc.onos.api.flowmanager.FlowBatchOperation.Operator;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.action.Action;
 import net.onrc.onos.core.matchaction.match.PacketMatch;
 import net.onrc.onos.core.matchaction.match.PacketMatchBuilder;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.PortNumber;
 
 /**
@@ -67,8 +68,8 @@
 
     @Override
     public List<MatchActionOperations> compile(Operator op,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         // TODO Auto-generated method stub
         return null;
     }
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/PacketPathFlow.java b/src/main/java/net/onrc/onos/api/flowmanager/PacketPathFlow.java
index 37820fb..34d6776 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/PacketPathFlow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/PacketPathFlow.java
@@ -10,13 +10,14 @@
 
 import net.onrc.onos.api.flowmanager.FlowBatchOperation.Operator;
 import net.onrc.onos.core.matchaction.MatchAction;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperationEntry;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.action.Action;
 import net.onrc.onos.core.matchaction.action.OutputAction;
 import net.onrc.onos.core.matchaction.match.PacketMatch;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.PortNumber;
 import net.onrc.onos.core.util.SwitchPort;
 
@@ -86,8 +87,8 @@
 
     @Override
     public List<MatchActionOperations> compile(Operator op,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         switch (op) {
         case ADD:
             return compileAddOperation(maIdGenerator, maoIdGenerator);
@@ -108,7 +109,7 @@
      */
     private MatchAction createNextMatchAction(Iterator<SwitchPort> portIterator,
             Iterator<List<Action>> actionsIterator,
-            MatchActionIdGenerator maIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator) {
         if (portIterator == null || actionsIterator == null ||
                 !portIterator.hasNext() || !actionsIterator.hasNext()) {
             return null;
@@ -128,8 +129,8 @@
      * @return the list of {@link MatchActionOperations} objects
      */
     private List<MatchActionOperations> compileAddOperation(
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         Path path = checkNotNull(getPath());
         checkState(path.size() > 0, "Path object has no link.");
 
@@ -183,8 +184,8 @@
      * @return the list of {@link MatchActionOperations} objects
      */
     private List<MatchActionOperations> compileRemoveOperation(
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         // TODO implement it
         throw new UnsupportedOperationException(
                 "REMOVE operation is not implemented yet.");
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java b/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
index 0caef51..d02351b 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
@@ -18,14 +18,15 @@
 
 import net.onrc.onos.api.flowmanager.FlowBatchOperation.Operator;
 import net.onrc.onos.core.matchaction.MatchAction;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperationEntry;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.action.Action;
 import net.onrc.onos.core.matchaction.action.OutputAction;
 import net.onrc.onos.core.matchaction.match.PacketMatch;
 import net.onrc.onos.core.util.Dpid;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.PortNumber;
 import net.onrc.onos.core.util.SwitchPort;
 
@@ -110,8 +111,8 @@
 
     @Override
     public List<MatchActionOperations> compile(Operator op,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         switch (op) {
         case ADD:
             return compileAddOperation(maIdGenerator, maoIdGenerator);
@@ -123,7 +124,7 @@
     }
 
     private MatchAction createMatchAction(SwitchPort port, List<Action> actions,
-            MatchActionIdGenerator maIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator) {
         checkNotNull(port);
         checkNotNull(actions);
 
@@ -145,8 +146,8 @@
             Dpid egressSwitch,
             Map<Dpid, Set<PortNumber>> inPorts,
             Map<Dpid, PortNumber> outPorts,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         MatchActionOperations firstOps =
                 new MatchActionOperations(maoIdGenerator.getNewId());
         for (Entry<Dpid, Set<PortNumber>> innerSw : inPorts.entrySet()) {
@@ -183,8 +184,8 @@
     private MatchActionOperations generateSecondAddOperations(
             Dpid egressSwitch,
             Map<Dpid, PortNumber> outPorts,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         MatchActionOperations secondOps =
                 new MatchActionOperations(maoIdGenerator.getNewId());
         for (SwitchPort port : getIngressPorts()) {
@@ -213,8 +214,8 @@
     }
 
     private List<MatchActionOperations> compileAddOperation(
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         checkNotNull(tree);
         checkState(tree.size() > 0, "Tree object has no link.");
 
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/SingleSrcTreeFlow.java b/src/main/java/net/onrc/onos/api/flowmanager/SingleSrcTreeFlow.java
index 3e70f4b..89f1efd 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/SingleSrcTreeFlow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/SingleSrcTreeFlow.java
@@ -6,12 +6,13 @@
 import java.util.Set;
 
 import net.onrc.onos.api.flowmanager.FlowBatchOperation.Operator;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.action.OutputAction;
 import net.onrc.onos.core.matchaction.match.PacketMatch;
 import net.onrc.onos.core.util.Dpid;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.SwitchPort;
 
 import org.apache.commons.lang3.tuple.Pair;
@@ -84,8 +85,8 @@
 
     @Override
     public List<MatchActionOperations> compile(Operator op,
-            MatchActionIdGenerator maIdGenerator,
-            MatchActionOperationsIdGenerator maoIdGenerator) {
+            IdGenerator<MatchActionId> maIdGenerator,
+            IdGenerator<MatchActionOperationsId> maoIdGenerator) {
         // TODO Auto-generated method stub
         return null;
     }
diff --git a/src/main/java/net/onrc/onos/api/newintent/IntentIdGenerator.java b/src/main/java/net/onrc/onos/api/newintent/IntentIdGenerator.java
deleted file mode 100644
index ec75c7b..0000000
--- a/src/main/java/net/onrc/onos/api/newintent/IntentIdGenerator.java
+++ /dev/null
@@ -1,19 +0,0 @@
-package net.onrc.onos.api.newintent;
-
-/**
- * This interface is for generator of IntentId.
- *
- * <p>
- * {@link #getNewId()} generates a globally unique {@link IntentId} instance
- * on each invocation. Application developers should not generate IntentId
- * by themselves. Instead use an implementation of this interface.
- * </p>
- */
-public interface IntentIdGenerator {
-    /**
-     * Generates a globally unique {@link IntentId} instance.
-     *
-     * @return a globally unique {@link IntentId} instance.
-     */
-    public IntentId getNewId();
-}
diff --git a/src/main/java/net/onrc/onos/core/flowmanager/FlowIdGeneratorWithIdBlockAllocator.java b/src/main/java/net/onrc/onos/core/flowmanager/FlowIdGeneratorWithIdBlockAllocator.java
index d502d93..e818932 100644
--- a/src/main/java/net/onrc/onos/core/flowmanager/FlowIdGeneratorWithIdBlockAllocator.java
+++ b/src/main/java/net/onrc/onos/core/flowmanager/FlowIdGeneratorWithIdBlockAllocator.java
@@ -1,20 +1,15 @@
 package net.onrc.onos.core.flowmanager;
 
-import static com.google.common.base.Preconditions.checkNotNull;
 import net.onrc.onos.api.flowmanager.FlowId;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
-import net.onrc.onos.core.util.IdBlock;
+import net.onrc.onos.core.util.AbstractBlockAllocatorBasedIdGenerator;
 import net.onrc.onos.core.util.IdBlockAllocator;
-import net.onrc.onos.core.util.UnavailableIdException;
 
 /**
  * Generates a global unique FlowId using
  * {@link IdBlockAllocator#allocateUniqueIdBlock()}.
  */
-public class FlowIdGeneratorWithIdBlockAllocator implements FlowIdGenerator {
-
-    private final IdBlockAllocator allocator;
-    private IdBlock idBlock;
+public class FlowIdGeneratorWithIdBlockAllocator
+        extends AbstractBlockAllocatorBasedIdGenerator<FlowId> {
 
     /**
      * Creates a FlowId generator instance using specified ID block allocator.
@@ -22,17 +17,11 @@
      * @param allocator the ID block allocator to be used
      */
     public FlowIdGeneratorWithIdBlockAllocator(IdBlockAllocator allocator) {
-        this.allocator = checkNotNull(allocator);
-        this.idBlock = allocator.allocateUniqueIdBlock();
+        super(allocator);
     }
 
     @Override
-    public synchronized FlowId getNewId() {
-        try {
-            return new FlowId(idBlock.getNextId());
-        } catch (UnavailableIdException e) {
-            idBlock = allocator.allocateUniqueIdBlock();
-            return new FlowId(idBlock.getNextId());
-        }
+    protected FlowId convertFrom(long value) {
+        return new FlowId(value);
     }
 }
diff --git a/src/main/java/net/onrc/onos/core/flowmanager/FlowManagerModule.java b/src/main/java/net/onrc/onos/core/flowmanager/FlowManagerModule.java
index 39499f4..14c63df 100644
--- a/src/main/java/net/onrc/onos/core/flowmanager/FlowManagerModule.java
+++ b/src/main/java/net/onrc/onos/core/flowmanager/FlowManagerModule.java
@@ -22,18 +22,18 @@
 import net.onrc.onos.api.flowmanager.FlowBatchOperation;
 import net.onrc.onos.api.flowmanager.FlowBatchOperation.Operator;
 import net.onrc.onos.api.flowmanager.FlowId;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
 import net.onrc.onos.api.flowmanager.FlowManagerFloodlightService;
 import net.onrc.onos.api.flowmanager.FlowManagerListener;
 import net.onrc.onos.core.datagrid.ISharedCollectionsService;
 import net.onrc.onos.core.matchaction.MatchActionFloodlightService;
-import net.onrc.onos.core.matchaction.MatchActionIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionId;
 import net.onrc.onos.core.matchaction.MatchActionOperationEntry;
 import net.onrc.onos.core.matchaction.MatchActionOperations;
-import net.onrc.onos.core.matchaction.MatchActionOperationsIdGenerator;
+import net.onrc.onos.core.matchaction.MatchActionOperationsId;
 import net.onrc.onos.core.matchaction.MatchActionService;
 import net.onrc.onos.core.registry.IControllerRegistryService;
 import net.onrc.onos.core.util.IdBlockAllocator;
+import net.onrc.onos.core.util.IdGenerator;
 
 /**
  * Manages a set of Flow objects, computes and maintains a set of Match-Action
@@ -45,8 +45,8 @@
     private ConflictDetectionPolicy conflictDetectionPolicy;
     private FlowIdGeneratorWithIdBlockAllocator flowIdGenerator;
     private FlowBatchIdGeneratorWithIdBlockAllocator flowBatchIdGenerator;
-    private MatchActionIdGenerator maIdGenerator;
-    private MatchActionOperationsIdGenerator maoIdGenerator;
+    private IdGenerator<MatchActionId> maIdGenerator;
+    private IdGenerator<MatchActionOperationsId> maoIdGenerator;
     private MatchActionService matchActionService;
     private IControllerRegistryService registryService;
     private ISharedCollectionsService sharedCollectionService;
@@ -155,7 +155,7 @@
     }
 
     @Override
-    public FlowIdGenerator getFlowIdGenerator() {
+    public IdGenerator<FlowId> getFlowIdGenerator() {
         return flowIdGenerator;
     }
 
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGenerator.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGenerator.java
deleted file mode 100644
index 4f36d7c..0000000
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGenerator.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package net.onrc.onos.core.matchaction;
-/**
-  * A generator of MatchActionId.
-  */
-public interface MatchActionIdGenerator {
-    /**
-      * Generates a globally unique MatchActionId instance.
-      */
-    MatchActionId getNewId();
-}
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGeneratorWithIdBlockAllocator.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGeneratorWithIdBlockAllocator.java
index 14a09c2..ef255d0 100644
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGeneratorWithIdBlockAllocator.java
+++ b/src/main/java/net/onrc/onos/core/matchaction/MatchActionIdGeneratorWithIdBlockAllocator.java
@@ -1,19 +1,13 @@
 package net.onrc.onos.core.matchaction;
 
-import net.onrc.onos.core.util.IdBlock;
+import net.onrc.onos.core.util.AbstractBlockAllocatorBasedIdGenerator;
 import net.onrc.onos.core.util.IdBlockAllocator;
-import net.onrc.onos.core.util.UnavailableIdException;
-
-import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
  * Generates a global unique MatchActionId.
  */
 public class MatchActionIdGeneratorWithIdBlockAllocator
-        implements MatchActionIdGenerator {
-
-    private final IdBlockAllocator allocator;
-    private IdBlock idBlock;
+        extends AbstractBlockAllocatorBasedIdGenerator<MatchActionId> {
 
     /**
      * Creates a FlowId generator instance using specified ID block allocator.
@@ -21,17 +15,11 @@
      * @param allocator the ID block allocator to be used
      */
     public MatchActionIdGeneratorWithIdBlockAllocator(IdBlockAllocator allocator) {
-        this.allocator = checkNotNull(allocator);
-        this.idBlock = allocator.allocateUniqueIdBlock();
+        super(allocator);
     }
 
     @Override
-    public synchronized MatchActionId getNewId() {
-        try {
-            return new MatchActionId(idBlock.getNextId());
-        } catch (UnavailableIdException e) {
-            idBlock = allocator.allocateUniqueIdBlock();
-            return new MatchActionId(idBlock.getNextId());
-        }
+    protected MatchActionId convertFrom(long value) {
+        return new MatchActionId(value);
     }
 }
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionModule.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionModule.java
index 78e528c..6ae5d5e 100644
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionModule.java
+++ b/src/main/java/net/onrc/onos/core/matchaction/MatchActionModule.java
@@ -7,6 +7,7 @@
 import java.util.Set;
 
 import net.onrc.onos.api.flowmanager.ConflictDetectionPolicy;
+import net.onrc.onos.core.util.IdGenerator;
 
 /**
  * Manages Match-Action entries.
@@ -56,14 +57,14 @@
     }
 
     @Override
-    public MatchActionIdGenerator getMatchActionIdGenerator() {
+    public IdGenerator<MatchActionId> getMatchActionIdGenerator() {
         // TODO Auto-generated method stub
         // use MatchActionIdGeneratorWithIdBlockAllocator.
         return null;
     }
 
     @Override
-    public MatchActionOperationsIdGenerator getMatchActionOperationsIdGenerator() {
+    public IdGenerator<MatchActionOperationsId> getMatchActionOperationsIdGenerator() {
         // TODO Auto-generated method stub
         // use MatchActionOperationsIdGeneratorWithIdBlockAllocator.
         return null;
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGenerator.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGenerator.java
deleted file mode 100644
index 3274224..0000000
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGenerator.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package net.onrc.onos.core.matchaction;
-/**
-  * A generator of MatchActionId.
-  */
-public interface MatchActionOperationsIdGenerator {
-    /**
-      * Generates a globally unique MatchActionId instance.
-      */
-    MatchActionOperationsId getNewId();
-}
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGeneratorWithIdBlockAllocator.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGeneratorWithIdBlockAllocator.java
index d1d5240..fd9efdc 100644
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGeneratorWithIdBlockAllocator.java
+++ b/src/main/java/net/onrc/onos/core/matchaction/MatchActionOperationsIdGeneratorWithIdBlockAllocator.java
@@ -1,37 +1,26 @@
 package net.onrc.onos.core.matchaction;
 
-import net.onrc.onos.core.util.IdBlock;
+import net.onrc.onos.core.util.AbstractBlockAllocatorBasedIdGenerator;
 import net.onrc.onos.core.util.IdBlockAllocator;
-import net.onrc.onos.core.util.UnavailableIdException;
 
-import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
  * Generates a global unique MatchActionIdId.
  */
 public class MatchActionOperationsIdGeneratorWithIdBlockAllocator
-        implements MatchActionOperationsIdGenerator {
+        extends AbstractBlockAllocatorBasedIdGenerator<MatchActionOperationsId> {
 
-        private final IdBlockAllocator allocator;
-        private IdBlock idBlock;
+    /**
+     * Creates a FlowId generator instance using specified ID block allocator.
+     *
+     * @param allocator the ID block allocator to be used
+     */
+    public MatchActionOperationsIdGeneratorWithIdBlockAllocator(IdBlockAllocator allocator) {
+        super(allocator);
+    }
 
-        /**
-          * Creates a FlowId generator instance using specified ID block allocator.
-          *
-          * @param allocator the ID block allocator to be used
-          */
-        public MatchActionOperationsIdGeneratorWithIdBlockAllocator(IdBlockAllocator allocator) {
-            this.allocator = checkNotNull(allocator);
-            this.idBlock = allocator.allocateUniqueIdBlock();
-        }
-
-        @Override
-        public synchronized MatchActionOperationsId getNewId() {
-            try {
-                return new MatchActionOperationsId(idBlock.getNextId());
-            } catch (UnavailableIdException e) {
-                idBlock = allocator.allocateUniqueIdBlock();
-                return new MatchActionOperationsId(idBlock.getNextId());
-            }
-        }
+    @Override
+    protected MatchActionOperationsId convertFrom(long value) {
+        return new MatchActionOperationsId(value);
+    }
 }
diff --git a/src/main/java/net/onrc/onos/core/matchaction/MatchActionService.java b/src/main/java/net/onrc/onos/core/matchaction/MatchActionService.java
index 161ed91..fa6b34f 100644
--- a/src/main/java/net/onrc/onos/core/matchaction/MatchActionService.java
+++ b/src/main/java/net/onrc/onos/core/matchaction/MatchActionService.java
@@ -4,6 +4,7 @@
 import java.util.Set;
 
 import net.onrc.onos.api.flowmanager.ConflictDetectionPolicy;
+import net.onrc.onos.core.util.IdGenerator;
 
 /**
  * An interface for the match-action service.
@@ -51,14 +52,14 @@
      *
      * @return the ID generator for MatchActionId
      */
-    MatchActionIdGenerator getMatchActionIdGenerator();
+    IdGenerator<MatchActionId> getMatchActionIdGenerator();
 
     /**
      * Gets the ID generator for MatchActionOperationsId.
      *
      * @return the ID generator for MatchActionOperationsId
      */
-    MatchActionOperationsIdGenerator getMatchActionOperationsIdGenerator();
+    IdGenerator<MatchActionOperationsId> getMatchActionOperationsIdGenerator();
 
     /**
      * Adds event listener to this service.
diff --git a/src/main/java/net/onrc/onos/core/newintent/AbstractFlowGeneratingIntentCompiler.java b/src/main/java/net/onrc/onos/core/newintent/AbstractFlowGeneratingIntentCompiler.java
index 07041e9..159caf5 100644
--- a/src/main/java/net/onrc/onos/core/newintent/AbstractFlowGeneratingIntentCompiler.java
+++ b/src/main/java/net/onrc/onos/core/newintent/AbstractFlowGeneratingIntentCompiler.java
@@ -1,9 +1,9 @@
 package net.onrc.onos.core.newintent;
 
 import net.onrc.onos.api.flowmanager.FlowId;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
 import net.onrc.onos.api.newintent.Intent;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
+import net.onrc.onos.api.newintent.IntentId;
+import net.onrc.onos.core.util.IdGenerator;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -15,17 +15,17 @@
 public abstract class AbstractFlowGeneratingIntentCompiler<T extends Intent>
         extends AbstractIntentCompiler<T> {
 
-    private final FlowIdGenerator flowIdGenerator;
+    private final IdGenerator<FlowId> flowIdGenerator;
 
     /**
-     * Constructs an object with the specified {@link IntentIdGenerator}
-     * and {@link FlowIdGenerator}.
+     * Constructs an object with the specified {@link IdGenerator IdGenerators} of intent ID
+     * and flow ID.
      *
      * @param intentIdGenerator
      * @param flowIdGenerator
      */
-    protected AbstractFlowGeneratingIntentCompiler(IntentIdGenerator intentIdGenerator,
-                                                   FlowIdGenerator flowIdGenerator) {
+    protected AbstractFlowGeneratingIntentCompiler(IdGenerator<IntentId> intentIdGenerator,
+                                                   IdGenerator<FlowId> flowIdGenerator) {
         super(intentIdGenerator);
         this.flowIdGenerator = checkNotNull(flowIdGenerator);
     }
diff --git a/src/main/java/net/onrc/onos/core/newintent/AbstractIntentCompiler.java b/src/main/java/net/onrc/onos/core/newintent/AbstractIntentCompiler.java
index 0b16f10..46f4cf9 100644
--- a/src/main/java/net/onrc/onos/core/newintent/AbstractIntentCompiler.java
+++ b/src/main/java/net/onrc/onos/core/newintent/AbstractIntentCompiler.java
@@ -4,10 +4,10 @@
 import net.onrc.onos.api.newintent.Intent;
 import net.onrc.onos.api.newintent.IntentCompiler;
 import net.onrc.onos.api.newintent.IntentId;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
 import net.onrc.onos.core.matchaction.action.Action;
 import net.onrc.onos.core.matchaction.action.Actions;
 import net.onrc.onos.core.matchaction.action.OutputAction;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.SwitchPort;
 
 import java.util.ArrayList;
@@ -20,7 +20,7 @@
  * @param <T> the type of intent
  */
 public abstract class AbstractIntentCompiler<T extends Intent> implements IntentCompiler<T> {
-    private final IntentIdGenerator idGenerator;
+    private final IdGenerator<IntentId> idGenerator;
 
     /**
      * Constructs an instance with the specified Intent ID generator.
@@ -32,7 +32,7 @@
      * </p>
      * @param idGenerator intent ID generator
      */
-    protected AbstractIntentCompiler(IntentIdGenerator idGenerator) {
+    protected AbstractIntentCompiler(IdGenerator<IntentId> idGenerator) {
         this.idGenerator = checkNotNull(idGenerator);
     }
 
diff --git a/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java b/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
index 9137b29..a89879a 100644
--- a/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
+++ b/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
@@ -1,21 +1,14 @@
 package net.onrc.onos.core.newintent;
 
 import net.onrc.onos.api.newintent.IntentId;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
-import net.onrc.onos.core.util.IdBlock;
+import net.onrc.onos.core.util.AbstractBlockAllocatorBasedIdGenerator;
 import net.onrc.onos.core.util.IdBlockAllocator;
-import net.onrc.onos.core.util.UnavailableIdException;
-
-import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * An implementation of {@link IntentIdGenerator},
- * which uses {@link IdBlockAllocator#allocateUniqueIdBlock()}.
+ * An implementation of {@link net.onrc.onos.core.util.IdGenerator} of intent ID,
+ * which uses {@link IdBlockAllocator}.
  */
-public class IdBlockAllocatorBasedIntentIdGenerator implements IntentIdGenerator {
-
-    private final IdBlockAllocator allocator;
-    private IdBlock idBlock;
+public class IdBlockAllocatorBasedIntentIdGenerator extends AbstractBlockAllocatorBasedIdGenerator<IntentId> {
 
     /**
      * Constructs an intent ID generator, which uses the specified ID block allocator
@@ -24,17 +17,11 @@
      * @param allocator the ID block allocator to use for generating intent IDs
      */
     public IdBlockAllocatorBasedIntentIdGenerator(IdBlockAllocator allocator) {
-        this.allocator = checkNotNull(allocator);
-        this.idBlock = allocator.allocateUniqueIdBlock();
+        super(allocator);
     }
 
     @Override
-    public synchronized IntentId getNewId() {
-        try {
-            return new IntentId(idBlock.getNextId());
-        } catch (UnavailableIdException e) {
-            idBlock = allocator.allocateUniqueIdBlock();
-            return new IntentId(idBlock.getNextId());
-        }
+    protected IntentId convertFrom(long value) {
+        return new IntentId(value);
     }
 }
diff --git a/src/main/java/net/onrc/onos/core/newintent/IntentFloodlightModule.java b/src/main/java/net/onrc/onos/core/newintent/IntentFloodlightModule.java
index fee5983..cf0e5e5 100644
--- a/src/main/java/net/onrc/onos/core/newintent/IntentFloodlightModule.java
+++ b/src/main/java/net/onrc/onos/core/newintent/IntentFloodlightModule.java
@@ -4,7 +4,7 @@
 import net.floodlightcontroller.core.module.FloodlightModuleException;
 import net.floodlightcontroller.core.module.IFloodlightModule;
 import net.floodlightcontroller.core.module.IFloodlightService;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
+import net.onrc.onos.api.flowmanager.FlowId;
 import net.onrc.onos.api.flowmanager.FlowManagerFloodlightService;
 import net.onrc.onos.api.flowmanager.FlowManagerService;
 import net.onrc.onos.api.newintent.InstallableIntent;
@@ -13,7 +13,6 @@
 import net.onrc.onos.api.newintent.IntentEventListener;
 import net.onrc.onos.api.newintent.IntentFloodlightService;
 import net.onrc.onos.api.newintent.IntentId;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
 import net.onrc.onos.api.newintent.IntentInstaller;
 import net.onrc.onos.api.newintent.IntentManager;
 import net.onrc.onos.api.newintent.IntentOperations;
@@ -25,6 +24,7 @@
 import net.onrc.onos.core.registry.IControllerRegistryService;
 import net.onrc.onos.core.topology.ITopologyService;
 import net.onrc.onos.core.util.IdBlockAllocator;
+import net.onrc.onos.core.util.IdGenerator;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -76,11 +76,11 @@
 
         IdBlockAllocator idBlockAllocator =
                 context.getServiceImpl(IControllerRegistryService.class);
-        IntentIdGenerator intentIdGenerator =
+        IdGenerator<IntentId> intentIdGenerator =
                 new IdBlockAllocatorBasedIntentIdGenerator(idBlockAllocator);
         FlowManagerService flowManagerService =
                 context.getServiceImpl(FlowManagerFloodlightService.class);
-        FlowIdGenerator flowIdGenerator =
+        IdGenerator<FlowId> flowIdGenerator =
                 flowManagerService.getFlowIdGenerator();
 
         ITopologyService topologyService =
@@ -90,8 +90,8 @@
         registerDefaultInstallers(flowManagerService);
     }
 
-    private void registerDefaultCompilers(IntentIdGenerator intentIdGenerator,
-                                          FlowIdGenerator flowIdGenerator,
+    private void registerDefaultCompilers(IdGenerator<IntentId> intentIdGenerator,
+                                          IdGenerator<FlowId> flowIdGenerator,
                                           ITopologyService topologyService) {
         intentManager.registerCompiler(PointToPointIntent.class,
                 new PointToPointIntentCompiler(intentIdGenerator,
diff --git a/src/main/java/net/onrc/onos/core/newintent/MultiPointToSinglePointIntentCompiler.java b/src/main/java/net/onrc/onos/core/newintent/MultiPointToSinglePointIntentCompiler.java
index eb31457..e5a9d25 100644
--- a/src/main/java/net/onrc/onos/core/newintent/MultiPointToSinglePointIntentCompiler.java
+++ b/src/main/java/net/onrc/onos/core/newintent/MultiPointToSinglePointIntentCompiler.java
@@ -1,10 +1,10 @@
 package net.onrc.onos.core.newintent;
 
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
+import net.onrc.onos.api.flowmanager.FlowId;
 import net.onrc.onos.api.flowmanager.SingleDstTreeFlow;
 import net.onrc.onos.api.flowmanager.Tree;
 import net.onrc.onos.api.newintent.Intent;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
+import net.onrc.onos.api.newintent.IntentId;
 import net.onrc.onos.api.newintent.MultiPointToSinglePointIntent;
 import net.onrc.onos.core.intent.ConstrainedBFSTree;
 import net.onrc.onos.core.intent.Path;
@@ -13,6 +13,7 @@
 import net.onrc.onos.core.topology.BaseTopology;
 import net.onrc.onos.core.topology.ITopologyService;
 import net.onrc.onos.core.topology.Switch;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.SwitchPort;
 
 import java.util.Arrays;
@@ -37,8 +38,8 @@
      * @param flowIdGenerator flow ID generator
      * @param topologyService topology service
      */
-    public MultiPointToSinglePointIntentCompiler(IntentIdGenerator intentIdGenerator,
-                                                 FlowIdGenerator flowIdGenerator,
+    public MultiPointToSinglePointIntentCompiler(IdGenerator<IntentId> intentIdGenerator,
+                                                 IdGenerator<FlowId> flowIdGenerator,
                                                  ITopologyService topologyService) {
         super(intentIdGenerator, flowIdGenerator);
         this.topologyService = checkNotNull(topologyService);
diff --git a/src/main/java/net/onrc/onos/core/newintent/PathIntentCompiler.java b/src/main/java/net/onrc/onos/core/newintent/PathIntentCompiler.java
index e7e2f87..0277050 100644
--- a/src/main/java/net/onrc/onos/core/newintent/PathIntentCompiler.java
+++ b/src/main/java/net/onrc/onos/core/newintent/PathIntentCompiler.java
@@ -3,15 +3,16 @@
 import com.google.common.base.Predicates;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableList;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
+import net.onrc.onos.api.flowmanager.FlowId;
 import net.onrc.onos.api.flowmanager.FlowLink;
 import net.onrc.onos.api.flowmanager.PacketPathFlow;
 import net.onrc.onos.api.flowmanager.Path;
 import net.onrc.onos.api.newintent.Intent;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
+import net.onrc.onos.api.newintent.IntentId;
 import net.onrc.onos.api.newintent.PathIntent;
 import net.onrc.onos.core.matchaction.match.Match;
 import net.onrc.onos.core.matchaction.match.PacketMatch;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.LinkTuple;
 
 import java.util.Arrays;
@@ -30,8 +31,8 @@
      * @param intentIdGenerator intent ID generator
      * @param flowIdGenerator flow ID generator
      */
-    public PathIntentCompiler(IntentIdGenerator intentIdGenerator,
-                              FlowIdGenerator flowIdGenerator) {
+    public PathIntentCompiler(IdGenerator<IntentId> intentIdGenerator,
+                              IdGenerator<FlowId> flowIdGenerator) {
         super(intentIdGenerator, flowIdGenerator);
     }
 
diff --git a/src/main/java/net/onrc/onos/core/newintent/PointToPointIntentCompiler.java b/src/main/java/net/onrc/onos/core/newintent/PointToPointIntentCompiler.java
index fcf718d..3c04e0d 100644
--- a/src/main/java/net/onrc/onos/core/newintent/PointToPointIntentCompiler.java
+++ b/src/main/java/net/onrc/onos/core/newintent/PointToPointIntentCompiler.java
@@ -4,12 +4,11 @@
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableList;
 import net.onrc.onos.api.flowmanager.FlowId;
-import net.onrc.onos.api.flowmanager.FlowIdGenerator;
 import net.onrc.onos.api.flowmanager.FlowLink;
 import net.onrc.onos.api.flowmanager.PacketPathFlow;
 import net.onrc.onos.api.flowmanager.Path;
 import net.onrc.onos.api.newintent.Intent;
-import net.onrc.onos.api.newintent.IntentIdGenerator;
+import net.onrc.onos.api.newintent.IntentId;
 import net.onrc.onos.api.newintent.PointToPointIntent;
 import net.onrc.onos.core.intent.ConstrainedBFSTree;
 import net.onrc.onos.core.matchaction.action.Action;
@@ -19,6 +18,7 @@
 import net.onrc.onos.core.topology.ITopologyService;
 import net.onrc.onos.core.topology.LinkEvent;
 import net.onrc.onos.core.topology.Switch;
+import net.onrc.onos.core.util.IdGenerator;
 import net.onrc.onos.core.util.SwitchPort;
 
 import java.util.Arrays;
@@ -41,8 +41,8 @@
      * @param intentIdGenerator intent ID generator
      * @param topologyService topology service
      */
-    public PointToPointIntentCompiler(IntentIdGenerator intentIdGenerator,
-                                      FlowIdGenerator flowIdGenerator,
+    public PointToPointIntentCompiler(IdGenerator<IntentId> intentIdGenerator,
+                                      IdGenerator<FlowId> flowIdGenerator,
                                       ITopologyService topologyService) {
         super(intentIdGenerator, flowIdGenerator);
         this.topologyService = checkNotNull(topologyService);
diff --git a/src/main/java/net/onrc/onos/core/util/AbstractBlockAllocatorBasedIdGenerator.java b/src/main/java/net/onrc/onos/core/util/AbstractBlockAllocatorBasedIdGenerator.java
new file mode 100644
index 0000000..851bb91
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/util/AbstractBlockAllocatorBasedIdGenerator.java
@@ -0,0 +1,40 @@
+package net.onrc.onos.core.util;
+
+/**
+ * Base class of {@link IdGenerator} implementations which use {@link IdBlockAllocator} as
+ * backend.
+ *
+ * @param <T> the type of ID
+ */
+public abstract class AbstractBlockAllocatorBasedIdGenerator<T> implements IdGenerator<T> {
+    protected final IdBlockAllocator allocator;
+    protected IdBlock idBlock;
+
+    /**
+     * Constructs an ID generator which use {@link IdBlockAllocator} as backend.
+     *
+     * @param allocator
+     */
+    protected AbstractBlockAllocatorBasedIdGenerator(IdBlockAllocator allocator) {
+        this.allocator = allocator;
+        this.idBlock = allocator.allocateUniqueIdBlock();
+    }
+
+    @Override
+    public synchronized T getNewId() {
+        try {
+            return convertFrom(idBlock.getNextId());
+        } catch (UnavailableIdException e) {
+            idBlock = allocator.allocateUniqueIdBlock();
+            return convertFrom(idBlock.getNextId());
+        }
+    }
+
+    /**
+     * Returns an ID instance of {@code T} type from the long value.
+     *
+     * @param value original long value
+     * @return ID instance
+     */
+    protected abstract T convertFrom(long value);
+}
diff --git a/src/main/java/net/onrc/onos/core/util/IdGenerator.java b/src/main/java/net/onrc/onos/core/util/IdGenerator.java
new file mode 100644
index 0000000..b735954
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/util/IdGenerator.java
@@ -0,0 +1,21 @@
+package net.onrc.onos.core.util;
+
+/**
+ * A generalized interface for ID generation
+ *
+ * {@link #getNewId()} generates a globally unique ID instance on
+ * each invocation.
+ *
+ * @param <T> the type of ID
+ */
+// TODO: do we need to define a base marker interface for ID,
+// then changed the type parameter to <T extends BaseId> something
+// like that?
+public interface IdGenerator<T> {
+    /**
+     * Returns a globally unique ID instance.
+     *
+     * @return globally unique ID instance
+     */
+    T getNewId();
+}
diff --git a/src/test/java/net/onrc/onos/api/flowmanager/FakeFlowManagerService.java b/src/test/java/net/onrc/onos/api/flowmanager/FakeFlowManagerService.java
index c231bca..50e68ce 100644
--- a/src/test/java/net/onrc/onos/api/flowmanager/FakeFlowManagerService.java
+++ b/src/test/java/net/onrc/onos/api/flowmanager/FakeFlowManagerService.java
@@ -2,6 +2,7 @@
 
 import com.google.common.collect.ImmutableList;
 import net.onrc.onos.core.flowmanager.FlowBatchHandleImpl;
+import net.onrc.onos.core.util.IdGenerator;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -87,7 +88,7 @@
     }
 
     @Override
-    public FlowIdGenerator getFlowIdGenerator() {
+    public IdGenerator<FlowId> getFlowIdGenerator() {
         throw new UnsupportedOperationException();
     }
 
diff --git a/src/test/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java b/src/test/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java
new file mode 100644
index 0000000..95087af
--- /dev/null
+++ b/src/test/java/net/onrc/onos/api/flowmanager/FlowIdGenerator.java
@@ -0,0 +1,10 @@
+package net.onrc.onos.api.flowmanager;
+
+import net.onrc.onos.core.util.IdGenerator;
+
+/**
+ * An generator of {@link FlowId}. It is defined only for
+ * testing purpose to keep type safety on mock creation.
+ */
+public interface FlowIdGenerator extends IdGenerator<FlowId> {
+}
diff --git a/src/test/java/net/onrc/onos/api/newintent/IntentIdGenerator.java b/src/test/java/net/onrc/onos/api/newintent/IntentIdGenerator.java
new file mode 100644
index 0000000..2f5e013
--- /dev/null
+++ b/src/test/java/net/onrc/onos/api/newintent/IntentIdGenerator.java
@@ -0,0 +1,16 @@
+package net.onrc.onos.api.newintent;
+
+import net.onrc.onos.core.util.IdGenerator;
+
+/**
+ * This interface is for generator of IntentId. It is defined only for
+ * testing purpose to keep type safety on mock creation.
+ *
+ * <p>
+ * {@link #getNewId()} generates a globally unique {@link IntentId} instance
+ * on each invocation. Application developers should not generate IntentId
+ * by themselves. Instead use an implementation of this interface.
+ * </p>
+ */
+public interface IntentIdGenerator extends IdGenerator<IntentId> {
+}