Java RocksDB安装与应用

rocksDB 是一个可嵌入的，持久性的 key-value存储。

以下介绍来自rocksDB 中文官网

https://rocksdb.org.cn/

它有以下四个特点

1 高性能：RocksDB使用一套日志结构的数据库引擎，为了更好的性能，这套引擎是用C++编写的。 Key和value是任意大小的字节流。

2 为快速存储而优化：RocksDB为快速而又低延迟的存储设备（例如闪存或者高速硬盘）而特殊优化处理。 RocksDB将最大限度的发挥闪存和RAM的高度率读写性能。

3 可适配性 ：RocksDB适合于多种不同工作量类型。 从像MyRocks这样的数据存储引擎， 到应用数据缓存, 甚至是一些嵌入式工作量，RocksDB都可以从容面对这些不同的数据工作量需求。

4 基础和高级的数据库操作  RocksDB提供了一些基础的操作，例如打开和关闭数据库。 对于合并和压缩过滤等高级操作，也提供了读写支持。

​​​​​​RockDB 安装与使用

rocksDB 安装有多种方式。由于官方没有提供对应平台的二进制库，所以需要自己编译使用。

rocksDB 的安装很简单，但是需要转变一下对于rocksDB 的看法。它不是一个重量级别的数据库，是一个嵌入式的key-value 存储。这意味着你只要在你的Maven项目中添加 rocksDB的依赖，就可以在开发环境中自我尝试了。如果你没有理解这点，你就可能会走入下面这两种不推荐的安装方式。

方式 一   去查看rocksDB 的官网 发现要写 一个C++ 程序（不推荐）

#include <assert>
#include "rocksdb/db.h"
rocksdb::DB* db;
rocksdb::Options options;
options.create_if_missing = true;
rocksdb::Status status =
 rocksdb::DB::Open(options, "/tmp/testdb", &db);
assert(status.ok());

创建一个数据库？？？？ 怎么和之前用的mysql 或者mongo 不一样，为啥没有一个start.sh 或者start.bat 之类的脚本。难道要我写。写完了编译发现还不知道怎么和rocksDB 库进行关联，怎么办，我C++都忘完了。

方式二  使用pyrocksDB （不推荐）

http://pyrocksdb.readthedocs.io/en/latest/installation.html

详细的安装文档见pyrocksDB 的官网安装文档。

以上两种方式对于熟悉C++ 或者python 的开发者来说都比较友好，但对于java 开发者来说不是太友好。

接下来就介绍第三种方式。

方式三 使用maven （推荐）

新建maven 项目，修改pom.xml 依赖里面添加

<dependency>
 <groupId>org.rocksdb</groupId>
 <artifactId>rocksdbjni</artifactId>
 <version>5.8.6</version>
</dependency>

可以选择你喜欢的版本。

然后更高maven 的语言级别，我这里全局设置为了1.8

<profiles>
 <profile>
 <id>jdk18</id>
 <activation>
  <activeByDefault>true</activeByDefault>
  <jdk>1.8</jdk>
 </activation>
 <properties>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
  <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
 </properties>
 </profile>
</profiles>

到这里，环境就装好了，是不是又回到了熟悉的java 世界。

然后copy 源码包下的一个类，在IDE中修改一下运行配置，加一个程序运行中数据库存储路径，就可以运行测试了 。我会在文章最后给出这个类。

运行控制台会有日志输出，同时也文件中也会出现一下新的文件。

后面会更新更多关于rockDB 开发API 的介绍，以及在生产中的应用，希望大家关注。

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).

import org.rocksdb.*;
import org.rocksdb.util.SizeUnit;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
public class RocksDBSample {
 static {
 RocksDB.loadLibrary();
 }
 public static void main(final String[] args) {
 if (args.length < 1) {
 System.out.println("usage: RocksDBSample db_path");
 System.exit(-1);
 }
 final String db_path = args[0];
 final String db_path_not_found = db_path + "_not_found";
 System.out.println("RocksDBSample");
 try (final Options options = new Options();
  final Filter bloomFilter = new BloomFilter(10);
  final ReadOptions readOptions = new ReadOptions()
  .setFillCache(false);
  final Statistics stats = new Statistics();
  final RateLimiter rateLimiter = new RateLimiter(10000000,10000, 10)) {
 try (final RocksDB db = RocksDB.open(options, db_path_not_found)) {
 assert (false);
 } catch (final RocksDBException e) {
 System.out.format("Caught the expected exception -- %s\n", e);
 }
 try {
 options.setCreateIfMissing(true)
  .setStatistics(stats)
  .setWriteBufferSize(8 * SizeUnit.KB)
  .setMaxWriteBufferNumber(3)
  .setMaxBackgroundCompactions(10)
  .setCompressionType(CompressionType.SNAPPY_COMPRESSION)
  .setCompactionStyle(CompactionStyle.UNIVERSAL);
 } catch (final IllegalArgumentException e) {
 assert (false);
 }
 assert (options.createIfMissing() == true);
 assert (options.writeBufferSize() == 8 * SizeUnit.KB);
 assert (options.maxWriteBufferNumber() == 3);
 assert (options.maxBackgroundCompactions() == 10);
 assert (options.compressionType() == CompressionType.SNAPPY_COMPRESSION);
 assert (options.compactionStyle() == CompactionStyle.UNIVERSAL);
 assert (options.memTableFactoryName().equals("SkipListFactory"));
 options.setMemTableConfig(
  new HashSkipListMemTableConfig()
  .setHeight(4)
  .setBranchingFactor(4)
  .setBucketCount(2000000));
 assert (options.memTableFactoryName().equals("HashSkipListRepFactory"));
 options.setMemTableConfig(
  new HashLinkedListMemTableConfig()
  .setBucketCount(100000));
 assert (options.memTableFactoryName().equals("HashLinkedListRepFactory"));
 options.setMemTableConfig(
  new VectorMemTableConfig().setReservedSize(10000));
 assert (options.memTableFactoryName().equals("VectorRepFactory"));
 options.setMemTableConfig(new SkipListMemTableConfig());
 assert (options.memTableFactoryName().equals("SkipListFactory"));
 options.setTableFormatConfig(new PlainTableConfig());
 // Plain-Table requires mmap read
 options.setAllowMmapReads(true);
 assert (options.tableFactoryName().equals("PlainTable"));
 options.setRateLimiter(rateLimiter);
 final BlockBasedTableConfig table_options = new BlockBasedTableConfig();
 table_options.setBlockCacheSize(64 * SizeUnit.KB)
  .setFilter(bloomFilter)
  .setCacheNumShardBits(6)
  .setBlockSizeDeviation(5)
  .setBlockRestartInterval(10)
  .setCacheIndexAndFilterBlocks(true)
  .setHashIndexAllowCollision(false)
  .setBlockCacheCompressedSize(64 * SizeUnit.KB)
  .setBlockCacheCompressedNumShardBits(10);
 assert (table_options.blockCacheSize() == 64 * SizeUnit.KB);
 assert (table_options.cacheNumShardBits() == 6);
 assert (table_options.blockSizeDeviation() == 5);
 assert (table_options.blockRestartInterval() == 10);
 assert (table_options.cacheIndexAndFilterBlocks() == true);
 assert (table_options.hashIndexAllowCollision() == false);
 assert (table_options.blockCacheCompressedSize() == 64 * SizeUnit.KB);
 assert (table_options.blockCacheCompressedNumShardBits() == 10);
 options.setTableFormatConfig(table_options);
 assert (options.tableFactoryName().equals("BlockBasedTable"));
 try (final RocksDB db = RocksDB.open(options, db_path)) {
 db.put("hello".getBytes(), "world".getBytes());
 final byte[] value = db.get("hello".getBytes());
 assert ("world".equals(new String(value)));
 final String str = db.getProperty("rocksdb.stats");
 assert (str != null && !str.equals(""));
 } catch (final RocksDBException e) {
 System.out.format("[ERROR] caught the unexpected exception -- %s\n", e);
 assert (false);
 }
 try (final RocksDB db = RocksDB.open(options, db_path)) {
 db.put("hello".getBytes(), "world".getBytes());
 byte[] value = db.get("hello".getBytes());
 System.out.format("Get('hello') = %s\n",
  new String(value));
 for (int i = 1; i <= 9; ++i) {
  for (int j = 1; j <= 9; ++j) {
  db.put(String.format("%dx%d", i, j).getBytes(),
  String.format("%d", i * j).getBytes());
  }
 }
 for (int i = 1; i <= 9; ++i) {
  for (int j = 1; j <= 9; ++j) {
  System.out.format("%s ", new String(db.get(
  String.format("%dx%d", i, j).getBytes())));
  }
  System.out.println("");
 }
 // write batch test
 try (final WriteOptions writeOpt = new WriteOptions()) {
  for (int i = 10; i <= 19; ++i) {
  try (final WriteBatch batch = new WriteBatch()) {
  for (int j = 10; j <= 19; ++j) {
  batch.put(String.format("%dx%d", i, j).getBytes(),
   String.format("%d", i * j).getBytes());
  }
  db.write(writeOpt, batch);
  }
  }
 }
 for (int i = 10; i <= 19; ++i) {
  for (int j = 10; j <= 19; ++j) {
  assert (new String(
  db.get(String.format("%dx%d", i, j).getBytes())).equals(
  String.format("%d", i * j)));
  System.out.format("%s ", new String(db.get(
  String.format("%dx%d", i, j).getBytes())));
  }
  System.out.println("");
 }
 value = db.get("1x1".getBytes());
 assert (value != null);
 value = db.get("world".getBytes());
 assert (value == null);
 value = db.get(readOptions, "world".getBytes());
 assert (value == null);
 final byte[] testKey = "asdf".getBytes();
 final byte[] testValue =
  "asdfghjkl;'?><MNBVCXZQWERTYUIOP{+_)(*&^%$#@".getBytes();
 db.put(testKey, testValue);
 byte[] testResult = db.get(testKey);
 assert (testResult != null);
 assert (Arrays.equals(testValue, testResult));
 assert (new String(testValue).equals(new String(testResult)));
 testResult = db.get(readOptions, testKey);
 assert (testResult != null);
 assert (Arrays.equals(testValue, testResult));
 assert (new String(testValue).equals(new String(testResult)));
 final byte[] insufficientArray = new byte[10];
 final byte[] enoughArray = new byte[50];
 int len;
 len = db.get(testKey, insufficientArray);
 assert (len > insufficientArray.length);
 len = db.get("asdfjkl;".getBytes(), enoughArray);
 assert (len == RocksDB.NOT_FOUND);
 len = db.get(testKey, enoughArray);
 assert (len == testValue.length);
 len = db.get(readOptions, testKey, insufficientArray);
 assert (len > insufficientArray.length);
 len = db.get(readOptions, "asdfjkl;".getBytes(), enoughArray);
 assert (len == RocksDB.NOT_FOUND);
 len = db.get(readOptions, testKey, enoughArray);
 assert (len == testValue.length);
 db.remove(testKey);
 len = db.get(testKey, enoughArray);
 assert (len == RocksDB.NOT_FOUND);
 // repeat the test with WriteOptions
 try (final WriteOptions writeOpts = new WriteOptions()) {
  writeOpts.setSync(true);
  writeOpts.setDisableWAL(true);
  db.put(writeOpts, testKey, testValue);
  len = db.get(testKey, enoughArray);
  assert (len == testValue.length);
  assert (new String(testValue).equals(
  new String(enoughArray, 0, len)));
 }
 try {
  for (final TickerType statsType : TickerType.values()) {
  if (statsType != TickerType.TICKER_ENUM_MAX) {
  stats.getTickerCount(statsType);
  }
  }
  System.out.println("getTickerCount() passed.");
 } catch (final Exception e) {
  System.out.println("Failed in call to getTickerCount()");
  assert (false); //Should never reach here.
 }
 try {
  for (final HistogramType histogramType : HistogramType.values()) {
  if (histogramType != HistogramType.HISTOGRAM_ENUM_MAX) {
  HistogramData data = stats.getHistogramData(histogramType);
  }
  }
  System.out.println("getHistogramData() passed.");
 } catch (final Exception e) {
  System.out.println("Failed in call to getHistogramData()");
  assert (false); //Should never reach here.
 }
 try (final RocksIterator iterator = db.newIterator()) {
  boolean seekToFirstPassed = false;
  for (iterator.seekToFirst(); iterator.isValid(); iterator.next()) {
  iterator.status();
  assert (iterator.key() != null);
  assert (iterator.value() != null);
  seekToFirstPassed = true;
  }
  if (seekToFirstPassed) {
  System.out.println("iterator seekToFirst tests passed.");
  }
  boolean seekToLastPassed = false;
  for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) {
  iterator.status();
  assert (iterator.key() != null);
  assert (iterator.value() != null);
  seekToLastPassed = true;
  }
  if (seekToLastPassed) {
  System.out.println("iterator seekToLastPassed tests passed.");
  }
  iterator.seekToFirst();
  iterator.seek(iterator.key());
  assert (iterator.key() != null);
  assert (iterator.value() != null);
  System.out.println("iterator seek test passed.");
 }
 System.out.println("iterator tests passed.");
 final List<byte[]> keys = new ArrayList<>();
 try (final RocksIterator iterator = db.newIterator()) {
  for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) {
  keys.add(iterator.key());
  }
 }
 Map<byte[], byte[]> values = db.multiGet(keys);
 assert (values.size() == keys.size());
 for (final byte[] value1 : values.values()) {
  assert (value1 != null);
 }
 values = db.multiGet(new ReadOptions(), keys);
 assert (values.size() == keys.size());
 for (final byte[] value1 : values.values()) {
  assert (value1 != null);
 }
 } catch (final RocksDBException e) {
 System.err.println(e);
 }
 }
 }
}

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