01 /*
02 *
03 * Licensed to the Apache Software Foundation (ASF) under one
04 * or more contributor license agreements. See the NOTICE file
05 * distributed with this work for additional information
06 * regarding copyright ownership. The ASF licenses this file
07 * to you under the Apache License, Version 2.0 (the
08 * "License"); you may not use this file except in compliance
09 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 *
20 */
21 package org.apache.qpid.server.txn;
22
23 import org.apache.qpid.AMQException;
24 import org.apache.qpid.server.store.StoreContext;
25
26 /**
27 * This provides the abstraction of an individual operation within a
28 * transaction. It is used by the TxnBuffer class.
29 */
30 public interface TxnOp
31 {
32 /**
33 * Do the part of the operation that updates persistent state
34 */
35 public void prepare(StoreContext context) throws AMQException;
36 /**
37 * Complete the operation started by prepare. Can now update in
38 * memory state or make netork transfers.
39 */
40 public void commit(StoreContext context) throws AMQException;
41 /**
42 * This is not the same as rollback. Unfortunately the use of an
43 * in memory reference count as a locking mechanism and a test for
44 * whether a message should be deleted means that as things are,
45 * handling an acknowledgement unavoidably alters both memory and
46 * persistent state on prepare. This is needed to 'compensate' or
47 * undo the in-memory change if the peristent update of later ops
48 * fails.
49 */
50 public void undoPrepare();
51 /**
52 * Rolls back the operation.
53 */
54 public void rollback(StoreContext context) throws AMQException;
55 }
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