1 files changed, 54 insertions, 0 deletions
diff --git a/java/java/broker/src/org/apache/qpid/server/txn/TxnOp.java b/java/java/broker/src/org/apache/qpid/server/txn/TxnOp.java
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index 0000000000..e863bab73e
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+++ b/java/java/broker/src/org/apache/qpid/server/txn/TxnOp.java
@@ -0,0 +1,54 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.qpid.server.txn;
+
+import org.apache.qpid.AMQException;
+
+/**
+ * This provides the abstraction of an individual operation within a
+ * transaction. It is used by the TxnBuffer class.
+ */
+public interface TxnOp
+{
+    /**
+     * Do the part of the operation that updates persistent state 
+     */
+    public void prepare() throws AMQException;
+    /**
+     * Complete the operation started by prepare. Can now update in
+     * memory state or make netork transfers.
+     */
+    public void commit();
+    /**
+     * This is not the same as rollback. Unfortunately the use of an
+     * in memory reference count as a locking mechanism and a test for
+     * whether a message should be deleted means that as things are,
+     * handling an acknowledgement unavoidably alters both memory and
+     * persistent state on prepare. This is needed to 'compensate' or
+     * undo the in-memory change if the peristent update of later ops
+     * fails.
+     */
+    public void undoPrepare();
+    /**
+     * Rolls back the operation.
+     */
+    public void rollback();
+}