levelkt

LevelDB client for Kotlin and/or Java 8+.

Initially project aimed to provide an alternative API for fusesource/leveldbjni's JNI layer fixing some of the issues around thread-safety, inefficient backward traversal, absent key-only iteration, Java 8 support. Later on, leveldbjni was replaced with protonail/leveldb-jna.

Compared to pure leveldb-jna, levelkt

hides the complexity associated with managing LevelDB Read/Write options
(while optimizing number of JNA calls),
provides convenient API for range/prefix queries, existence checks and
makes it easier not to leak resources (you only need to close LevelDB, LevelDBSnapshot and LevelDBCursor instances (it will also warn you if you don't)).

Usage

<dependency>
    <groupId>com.github.shyiko.levelkt</groupId>
    <artifactId>levelkt</artifactId>
    <version>0.1.0</version>
    <!-- omit classifier below if you plan to use this library in koltin -->
    <classifier>kalvanized</classifier>
</dependency>

(example) Kotlin

import com.github.shyiko.levelkt.jna.JNALevelDB

JNALevelDB("/tmp/0.leveldb").use { levelDB ->

    levelDB.put("key1".toByteArray(), "value1".toByteArray())
    levelDB.put("key2.1".toByteArray(), "value2.1".toByteArray())
    levelDB.put("key2.2".toByteArray(), "value2.2".toByteArray())
    levelDB.put("key3".toByteArray(), "value3".toByteArray())

    assert(levelDB.get("key1".toByteArray())?.let { String(it) } == "value1")

    assert(levelDB.keySlice("key".toByteArray(), offset = 1, limit = 2).map { String(it) } == 
        listOf("key2.1", "key2.2"))
    assert(levelDB.keySlice("key2".toByteArray(), "key3".toByteArray()).map { String(it) } == 
        listOf("key2.1", "key2.2"))
    assert(levelDB.keySliceByPrefix("key2".toByteArray()).map { String(it) } == 
        listOf("key2.1", "key2.2"))

    levelDB.keyCursor().use { cursor ->
        assert(cursor.seek("key2".toByteArray())?.let { String(it) } == "key2.1")
        assert(cursor.next()?.let { String(it) } == "key2.2")
    }

    // slice/sliceByPrefix/cursor look exactly the same as keySlice/keySliceByPrefix/keyCursor
    // the only difference - they operate with LevelDBRecord instead of ByteArray

    levelDB.batch {
        put("key1".toByteArray(), "value1.updated".toByteArray())
        del("key3".toByteArray())
    }

    levelDB.del("key1".toByteArray())
    
}

(example) Java 8+

import com.github.shyiko.levelkt.LevelDB;
import com.github.shyiko.levelkt.jna.JNALevelDB;

try (LevelDB levelDB = new JNALevelDB("/tmp/0.levedb")) {

    levelDB.batch(batch -> batch
        .put("key1".getBytes(), "value1".getBytes())
        .put("key2.1".getBytes(), "value2.1".getBytes())
        .put("key2.2".getBytes(), "value2.2".getBytes())
        .put("key3".getBytes(), "value3".getBytes())
    );

    assert levelDB
        .sliceByPrefix("key2".getBytes())
        .stream()
        .map(record -> new String(record.getKey()) + "=" + new String(record.getValue()))
        .collect(Collectors.toList())
        .equals(Arrays.asList("key2.1=value2.1", "key2.2=value2.2"));

}

Development

git clone https://github.com/shyiko/levelkt && cd levelkt
./mvnw # shows how to build, test, etc. project

Legal

All code, unless specified otherwise, is licensed under the MIT license.
Copyright (c) 2017 Stanley Shyiko.