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.
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