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Asked: 2026-05-17T22:29:10+00:00

I am looking for an embeddable library for doing atomic file I/O from java.

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I am looking for an embeddable library for doing atomic file I/O from java. I need the library to support the following features.

  • basic page management — allocate/free pages and read/write
  • atomic (all or nothing) writes (basically journaled I/O)

  • A simple binary page format (needs to be readable by C++)

  • It does not need to be that fast (or concurrent), just simple and reliable.

Has anyone used something in the past which fits the bill?

Things I have looked into

I found the internals for the kaha db project to be useful, but development seems to have switched to a fusesoure project called hawtdb. Hawt currently seems to rely memory mapped I/O which sounds good at first, but limits the size of the page file you can access to 2GB unless you go to a 64bit JVM + OS (due to JVM address space limitations).

Some alternatives I am considering are the Cassandra project, but I don’t know if its embeddable. I’ve looked into derby (which created lots of files when run) and H2 (which seemed promising, but I didn’t look too deeply). These seemed to have relatively complex page file formats and seem to provide far more than I need. MySQL did provide docs for the page file format, but it too was a bit complex.

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1 Answer

  1. Editorial Team

    HOWL

    HOWL is a logger implementation providing features required by the ObjectWeb JOTM project, with a public API that is generally usable by any Transaction Manager. HOWL uses unformatted binary logs to maximize performance and specifies a journalization API with methods necessary to support JOTM recovery operations.

    HOWL is intended to be used for logging of temporary data such as XA transaction events

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