Refactor transaction support in preparation for migration to latest APIs
 - Added a explicit transaction id type
 - cli command now just returns the identifiers of in-progress transactions
 - Removed redriveTransactions until a better alternative is provided
 - Removed DatabaseUpdate and replaced its usage with MapUpdate

Change-Id: Ic4a14967072068834510cd8459fd2a6790e456ef
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/Transaction.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/Transaction.java
new file mode 100644
index 0000000..ac5238a
--- /dev/null
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/Transaction.java
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.store.primitives.impl;
+
+import java.util.List;
+
+import org.onosproject.store.primitives.TransactionId;
+import org.onosproject.store.primitives.resources.impl.MapUpdate;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.ImmutableList;
+
+/**
+ * An immutable transaction object.
+ */
+public class Transaction {
+
+    enum State {
+        /**
+         * Indicates a new transaction that is about to be prepared. All transactions
+         * start their life in this state.
+         */
+        PREPARING,
+
+        /**
+         * Indicates a transaction that is successfully prepared i.e. all participants voted to commit
+         */
+        PREPARED,
+
+        /**
+         * Indicates a transaction that is about to be committed.
+         */
+        COMMITTING,
+
+        /**
+         * Indicates a transaction that has successfully committed.
+         */
+        COMMITTED,
+
+        /**
+         * Indicates a transaction that is about to be rolled back.
+         */
+        ROLLINGBACK,
+
+        /**
+         * Indicates a transaction that has been rolled back and all locks are released.
+         */
+        ROLLEDBACK
+    }
+
+    private final TransactionId transactionId;
+    private final List<MapUpdate<String, byte[]>> updates;
+    private final State state;
+
+    public Transaction(TransactionId transactionId, List<MapUpdate<String, byte[]>> updates) {
+        this(transactionId, updates, State.PREPARING);
+    }
+
+    private Transaction(TransactionId transactionId,
+            List<MapUpdate<String, byte[]>> updates,
+            State state) {
+        this.transactionId = transactionId;
+        this.updates = ImmutableList.copyOf(updates);
+        this.state = state;
+    }
+
+    public TransactionId id() {
+        return transactionId;
+    }
+
+    public List<MapUpdate<String, byte[]>> updates() {
+        return updates;
+    }
+
+    public State state() {
+        return state;
+    }
+
+    public Transaction transition(State newState) {
+        return new Transaction(transactionId, updates, newState);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("transactionId", transactionId)
+                .add("updates", updates)
+                .add("state", state)
+                .toString();
+    }
+}
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