Examples of JournalWriter

• org.fcrepo.server.journal.JournalWriter

  The abstract base for all JournalWriter classes.

  Each child class is responsible for providing an XMLEventWriter that will receive the JournalEntry tag. This class will format a JournalEntry object into XML and add it to the XMLEventWriter.

  Note that the writing of an entry is necessarily a three step process, consisting of

  1. calling {@link #prepareToWriteJournalEntry()},
  2. invoking the management method,
  3. calling {@link #writeJournalEntry(CreatorJournalEntry)}

  Several factors combine to require this sequence.

  • Each new journal file starts with a repository hash.
  • Repository hashes are expensive to calculate (on the order of 10 seconds). We don't want to calculate a hash unless it is needed for a new journal file.
  • We cannot predict in advance which journal entry will require that a new journal file be opened. The preceding file may be closed asynchronously as a result of a period of inactivity.
  • The repository hash must be calculated before the management method is invoked, so the receiver can confirm the file before making any changes to its own repository.
  • The journal entry must be written after the management method is invoked. The management method may add values to the context object in the {@link CreatorJournalEntry}, and these values must be written to the journal.

  @author Jim Blake

Examples of org.fcrepo.server.journal.JournalWriter