LevelDb JNI

This library gives you a java interface to the LevelDB C++ library - extremely fast for writing, compact key-value database.

How to use

Start by adding compiled/leveldbjni-1.122.0.jar to your project.

Then add required imports:

import com.github.vallez.leveldbjni.LevelDb;
import java.io.File;

Open database, don't forget to close it:

LevelDb.Options options = new LevelDb.Options();
options.setCreateIfMissing(true);
options.setErrorIfExists(false);
try (LevelDb db = new LevelDb(new File("testdb"), options)) {
    ... use it here
}

Reads And Writes

byte[] key = "a".getBytes();
byte[] value = "a value".getBytes();
db.put(key, value);
value = db.get(key);
db.delete(key);

Atomic Updates

if (db.get(key1) != null) {
    try (LevelDb.WriteBatch writeBatch = db.createWriteBatch()) {
        writeBatch.delete(key1);
        writeBatch.put(key2, value);
    } //you can either call writeBatch.write() or close it to commit
}

Iteration

It doesn't provide Java's Iterator interface to keep it faster.

Forward iteration

try (LevelDb.Iterator it = db.iterator()) {
    for (it.seekToFirst(); it.isValid(); it.next()) {
        byte[] key = it.key();
        byte[] value = it.value();
    }
}

Backward iteration

try (LevelDb.Iterator it = db.iterator()) {
    for (it.seekToLast(); it.isValid(); it.prev()) {
        byte[] key = it.key();
        byte[] value = it.value();
    }
}

Iteration for a key

try (LevelDb.Iterator it = db.iterator()) {
    for (it.seek(key); it.isValid(); it.prev()) {
        byte[] key = it.key();
        byte[] value = it.value();
    }
}