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/*
*
* 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();
}
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