LmdbJava provides an extremely low latency JNR-FFI-based binding to the LMDB native library. LMDB is an ultra-fast, ultra-compact, b-tree ordered, embedded, key-value store developed by Symas for the OpenLDAP Project.

LMDB uses memory-mapped files, so it has the read performance of a pure in-memory database while still offering the persistence of standard disk-based databases. It is transactional with full ACID semantics and crash-proof by design. No journal files. No corruption. No startup time. No dependencies. No config tuning. LMDB is the perfect foundation for large, read-centric, single node workloads that require strong latency and operational robustness outcomes.

Windows, Linux and OS X users can simply add the LmdbJava JAR to their classpath and start using the LmdbJava API (we bundle the LMDB libraries inside the JAR). If you prefer to use a shared system library, set the lmdbjava.disable.extract Library property to true.

Other operating systems will need to install the LMDB system library separately. The standard operating system package manager will likely work, but if you'd rather an up-to-date, tested, better-supported integration, try adapting the LmdbJava Native cross-compile targets.

Have a read through the tutorial to learn how to use LmdbJava.

We're happy to help you use LmdbJava. Simply open a GitHub issue if you have any questions.

Contributions are welcome! Please see the Contributing Guidelines.

For years Java users have been able to access LMDB via LMDBJNI. Its public API is mature and widely used, but this makes it challenging to implement any substantial changes.

LmdbJava was created to provide a new LMDB abstraction without the backward compatibility consideration. A separate project also offered a convenient opportunity to implement many internal changes to reduce latency and long-term maintenance costs. For example, we moved from HawtJNI to JNR-FFI (for its active community, lower latency, Java 9 roadmap and much simpler build requirements). We also significantly reduced and isolated Unsafe use, with only a single method now requiring it (and there is an automatic reflective fallback if Unsafe isn't available). Overall these changes make LmdbJava the optimal choice for projects targeting server-class JVMs, and it will be easy to support Java 9 when released.

This project is licensed under the Apache License, Version 2.0.

This project distribution JAR includes LMDB, which is licensed under The OpenLDAP Public License.