SequenceNumberCreator xref

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    1   /***
    2    *
    3    * Copyright 2004 Protique Ltd
    4    *
    5    * Licensed under the Apache License, Version 2.0 (the "License");
    6    * you may not use this file except in compliance with the License.
    7    * You may obtain a copy of the License at
    8    *
    9    * http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   **/
    18  package org.codehaus.activemq.store.bdb;
    19
    20  import com.sleepycat.je.CursorConfig;
    21  import com.sleepycat.je.DatabaseEntry;
    22  import com.sleepycat.je.DatabaseException;
    23  import com.sleepycat.je.LockMode;
    24  import com.sleepycat.je.OperationStatus;
    25  import com.sleepycat.je.SecondaryCursor;
    26  import com.sleepycat.je.SecondaryDatabase;
    27  import com.sleepycat.je.SecondaryKeyCreator;
    28  import org.apache.commons.logging.Log;
    29  import org.apache.commons.logging.LogFactory;
    30
    31  import javax.jms.JMSException;
    32
    33  /***
    34   * @version $Revision: 1.1 $
    35   */
    36  public class SequenceNumberCreator implements SecondaryKeyCreator {
    37      private static final Log log = LogFactory.getLog(SequenceNumberCreator.class);
    38
    39      private long counter = 1;
    40      private ThreadLocal lastKeyStore = new ThreadLocal();
    41      private ThreadLocal deleteKeyStore = new ThreadLocal();
    42
    43      public synchronized void initialise(SecondaryDatabase database) throws JMSException, DatabaseException {
    44          // lets calculate the size
    45          counter = queryLatestKeyInDatabase(database);
    46      }
    47
    48      public boolean createSecondaryKey(SecondaryDatabase secondaryDatabase, DatabaseEntry keyEntry, DatabaseEntry valueEntry, DatabaseEntry resultEntry) throws DatabaseException {
    49          DatabaseEntry nextKey = (DatabaseEntry) deleteKeyStore.get();
    50          if (nextKey != null) {
    51              resultEntry.setData(nextKey.getData());
    52              deleteKeyStore.set(null);
    53          }
    54          else {
    55              long value = 1;
    56              synchronized (this) {
    57                  value = ++counter;
    58              }
    59              //System.out.println("Creating new counter key of value: " + value);
    60              resultEntry.setData(BDbHelper.asBytes(value));
    61          }
    62          lastKeyStore.set(resultEntry);
    63          return true;
    64      }
    65
    66      /***
    67       * @return the last primary key we created
    68       */
    69      public DatabaseEntry getLastKey() {
    70          return (DatabaseEntry) lastKeyStore.get();
    71      }
    72
    73      /***
    74       * Sets the next primary key to return, such as doing a delete
    75       *
    76       * @param nextKey
    77       */
    78      public void setDeleteKey(DatabaseEntry nextKey) {
    79          this.deleteKeyStore.set(nextKey);
    80      }
    81
    82      protected long queryLatestKeyInDatabase(SecondaryDatabase database) throws JMSException, DatabaseException {
    83          CursorConfig cursorConfig = null;
    84          SecondaryCursor cursor = null;
    85          try {
    86              cursor = database.openSecondaryCursor(BDbHelper.getTransaction(), cursorConfig);
    87              DatabaseEntry sequenceNumberEntry = new DatabaseEntry();
    88              DatabaseEntry keyEntry = new DatabaseEntry();
    89              DatabaseEntry valueEntry = new DatabaseEntry();
    90              OperationStatus status = cursor.getLast(sequenceNumberEntry, keyEntry, valueEntry, LockMode.DEFAULT);
    91              long answer = 1;
    92              if (status != OperationStatus.NOTFOUND) {
    93                  if (status == OperationStatus.SUCCESS) {
    94                      answer = extractLong(sequenceNumberEntry);
    95                  }
    96                  else {
    97                      throw new JMSException("Invalid status code: " + status + " cannot read last sequence number");
    98                  }
    99              }
    100             return answer;
    101         }
    102         finally {
    103             if (cursor != null) {
    104                 try {
    105                     cursor.close();
    106                 }
    107                 catch (DatabaseException e) {
    108                     log.warn("Error closing cursor: " + e, e);
    109                 }
    110             }
    111         }
    112     }
    113
    114     protected long extractLong(DatabaseEntry entry) {
    115         return BDbHelper.longFromBytes(entry.getData());
    116     }
    117 }