LevelDB JNI

Description

LevelDB JNI gives you a Java interface to the LevelDB C++ library which is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.

Declaration

This LevelDB JNI is based on leveldb-1.23 and snappy-1.1.9 .

Maybe you need this LevelDB JNI ?

Strong Attention

NOTE: If you are using org.fusesource.leveldbjni/leveldbjni-all/1.8 Here's what you need to know this jni:

• suspendCompactions and resumeCompactions are no longer supported.
• 1.23.1 +, iterator.prev() changed, see change

Getting the JAR

Just add the following jar to your java project: leveldbjni-all-1.23.1.jar

Using the Dependency

gradle

       dependencies {
	        implementation 'com.halibobor:leveldbjni-all:1.23.1'
	   }

maven

        <dependency>
            <groupId>com.halibobor</groupId>
            <artifactId>leveldbjni-all</artifactId>
            <version>1.23.1</version>
        </dependency>

API Usage:

Recommended Package imports:

    import org.iq80.leveldb.*;
    import static org.fusesource.leveldbjni.JniDBFactory.*;
    import java.io.*;

Opening and closing the database.

    Options options = new Options();
    options.createIfMissing(true);
    DB db = factory.open(new File("example"), options);
    try {
      // Use the db in here....
    } finally {
      // Make sure you close the db to shutdown the 
      // database and avoid resource leaks.
      db.close();
    }

Putting, Getting, and Deleting key/values.

    db.put(bytes("Tampa"), bytes("rocks"));
    String value = asString(db.get(bytes("Tampa")));
    db.delete(bytes("Tampa"));

Performing Batch/Bulk/Atomic Updates.

    WriteBatch batch = db.createWriteBatch();
    try {
      batch.delete(bytes("Denver"));
      batch.put(bytes("Tampa"), bytes("green"));
      batch.put(bytes("London"), bytes("red"));

      db.write(batch);
    } finally {
      // Make sure you close the batch to avoid resource leaks.
      batch.close();
    }

Iterating key/values.

    DBIterator iterator = db.iterator();
    try {
      for(iterator.seekToFirst(); iterator.Valid(); iterator.next()) {
        String key = asString(iterator.key());
        String value = asString(iterator.value());
        System.out.println(key+" = "+value);
      }
    } finally {
      // Make sure you close the iterator to avoid resource leaks.
      iterator.close();
    }
    try {
      for(iterator.seekToLast(); iterator.Valid(); iterator.prev()) {
        String key = asString(iterator.key());
        String value = asString(iterator.value());
        System.out.println(key+" = "+value);
      }
    } finally {
      // Make sure you close the iterator to avoid resource leaks.
      iterator.close();
    }

Working against a Snapshot view of the Database.

    ReadOptions ro = new ReadOptions();
    ro.snapshot(db.getSnapshot());
    try {
      
      // All read operations will now use the same 
      // consistent view of the data.
      ... = db.iterator(ro);
      ... = db.get(bytes("Tampa"), ro);

    } finally {
      // Make sure you close the snapshot to avoid resource leaks.
      ro.snapshot().close();
    }

Using a custom Comparator.

    DBComparator comparator = new DBComparator(){
        public int compare(byte[] key1, byte[] key2) {
            return new String(key1).compareTo(new String(key2));
        }
        public String name() {
            return "simple";
        }
        public byte[] findShortestSeparator(byte[] start, byte[] limit) {
            return start;
        }
        public byte[] findShortSuccessor(byte[] key) {
            return key;
        }
    };
    Options options = new Options();
    options.comparator(comparator);
    DB db = factory.open(new File("example"), options);  

Disabling Compression.

    Options options = new Options();
    options.compressionType(CompressionType.NONE);
    DB db = factory.open(new File("example"), options);

Configuring the Cache.

    Options options = new Options();
    options.cacheSize(100 * 1048576); // 100MB cache
    DB db = factory.open(new File("example"), options);

Configuring the BloomFilter.

    Options options = new Options();
    options.bitsPerKey(10);
    DB db = factory.open(new File("example"), options);

Getting approximate sizes.

    long[] sizes = db.getApproximateSizes(new Range(bytes("a"), bytes("k")), new Range(bytes("k"), bytes("z")));
    System.out.println("Size: "+sizes[0]+", "+sizes[1]);

Getting database status.

    String stats = db.getProperty("leveldb.stats");
    System.out.println(stats);

Getting database approximate-memory-usage.

    String approximate = db.getProperty("leveldb.approximate-memory-usage");
    System.out.println(approximate);

Getting informational log messages.

    Logger logger = new Logger() {
      public void log(String message) {
        System.out.println(message);
      }
    };
    Options options = new Options();
    options.logger(logger);
    DB db = factory.open(new File("example"), options);

Destroying a database.

    Options options = new Options();
    factory.destroy(new File("example"), options);

Repairing a database.

    Options options = new Options();
    factory.repair(new File("example"), options);

Using a memory pool to make native memory allocations more efficient:

    JniDBFactory.pushMemoryPool(1024 * 512);
    try {
        // .. work with the DB in here, 
    } finally {
        JniDBFactory.popMemoryPool();
    }

Building

The following Steps work on mac, linux well, other platforms are not verified yet.

Welcome to contribute to other platforms.

Supported Platforms

The following worked for me on:

• OS X Mojave with X Code 11 (x86_64)
• OS X Monterey with X Code 13 (aarch64)
• CentOS (x86_64 | i386 | aarch64)

Prerequisites

• GNU compiler toolchain,gcc-c++
• openssl, openssl-devel(cmake required)
• JAVA(1.8+)，make sure the current session $JAVA_HOME is set.
• cmake3.1+
• git
• maven3
• automake
• autoconf
• pkg-configls,build-essential,libtool (linux maybe required)

Build Procedure

Then download the snappy, leveldb, leveldbjni,leveldbjni-all project source code.

git clone https://github.com/halibobor/leveldbjni-all.git
cd leveldbjni-all
git submodule update --init --recursive
cd third_party

1. snappy

    cd snappy
    mkdir build && cd build
    cmake -DCMAKE_BUILD_TYPE=Release ../
    make && make DESTDIR=/tmp install
    cd ../../

2. leveldb

    cd leveldb
    export LIBRARY_PATH=/tmp/usr/local/lib
    # export LIBRARY_PATH=/tmp/usr/local/lib64
    export CPLUS_INCLUDE_PATH=/tmp/usr/local/include
    mkdir build && cd build
    cmake -DCMAKE_BUILD_TYPE=Release .. && cmake --build .
    ./db_test
    ./db_bench
    make DESTDIR=/tmp install
    cd ../../

3. leveldbjni

    cd leveldbjni
    export SNAPPY_HOME=/tmp/usr/local
    export LEVELDB_HOME=/tmp/usr/local
    mvn clean package -P ${platform}

Replace ${platform} with one of the following platform identifiers (depending on the platform your building on):

• osx
• linux32
• linux64
• linux64-aarch64
• linux64-ppc64le
• linux64-sunos64-amd64
• linux64-sunos64-sparcv9
• win32
• win64
• freebsd64

Build Results

• leveldbjni-${platform}/target/native-build/target/lib/leveldbjni-${version}.[jnilib|so|dll] : native library using your currently platform.
• leveldbjni/target/leveldbjni-${version}-native-src.zip : A GNU style source project which you can use to build the native library on other systems.
• leveldbjni-${platform}/target/leveldbjni-${platform}-${version}.jar : A jar file containing the built native library using your currently platform.

4. leveldbjni-all

    git clone https://github.com/halibobor/leveldbjni-all.git
    cd leveldbjni-all
    cd src/main/resources/META-INF/
    # mkdir for native library
    mkdir -p ${os}${bit-model}/${arch}
    # cp  native library  to ${os}${bit-model}/${arch}
    cp ${native_library_path}/leveldbjni-1.23.jnilib  ${os}${bit-model}/${arch}
    # update pom.xml
    # add new config to Bundle-NativeCode
    # such as META-INF/native/osx64/aarch64/libleveldbjni.jnilib;osname=macosx;processor=aarch64
    mvn clean install

${os},${bit-model},${arch} values, such as osx,64,x86_64.

${platform}=${os}${bit-model},such as osx64.

Please refer to Library.java to get more.

Build Results

• leveldbjni/target/leveldbjni-all-${version}.jar : The java class file to the library.