org.exist.storage.journal
Class JournalReader

java.lang.Object
  org.exist.storage.journal.JournalReader

public class JournalReader
extends Object

Read log entries from the journal file. This class is used during recovery to scan the last journal file. It uses a memory-mapped byte buffer on the file. Journal entries can be read forward (during redo) or backward (during undo).

Author:

wolf

Constructor Summary

JournalReader(DBBroker broker, File file, int fileNumber)
Opens the specified file for reading.

Method Summary

void	close()
Loggable	lastEntry()
Loggable	nextEntry() Returns the next entry found from the current position.
void	position(long lsn) Re-position the file position so it points to the start of the entry with the given LSN.
Loggable	previousEntry() Returns the previous entry found by scanning backwards from the current position.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JournalReader

public JournalReader(DBBroker broker,
                     File file,
                     int fileNumber)
              throws LogException

Opens the specified file for reading.

Parameters:

broker -

file -

fileNumber -

Throws:

LogException

Method Detail

nextEntry

public Loggable nextEntry()
                   throws LogException

Returns the next entry found from the current position.

Returns:

the next entry

Throws:

LogException - if an entry could not be read due to an inconsistency on disk.

previousEntry

public Loggable previousEntry()
                       throws LogException

Returns the previous entry found by scanning backwards from the current position.

Returns:

the previous entry

Throws:

LogException - if an entry could not be read due to an inconsistency on disk.

LogException

lastEntry

public Loggable lastEntry()
                   throws LogException

Throws:

LogException

position

public void position(long lsn)
              throws LogException

Re-position the file position so it points to the start of the entry with the given LSN.

Parameters:

lsn -

Throws:

LogException

close

public void close()