嵌入内存的NoSQL键值数据库MapDB，Java

小鱼儿 2023-09-27 10:11 97阅读 0赞

## 嵌入内存的NoSQL键值数据库MapDB，Java ##

MapDB开源地址：

[GitHub - jankotek/mapdb: MapDB provides concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.MapDB provides concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine. - GitHub - jankotek/mapdb: MapDB provides concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.![fluidicon.png][]https://github.com/jankotek/mapdb][GitHub - jankotek_mapdb_ MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine. - GitHub - jankotek_mapdb_ MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine._fluidicon.png_https_github.com_jankotek_mapdb]

MapDB在maven的地址：

[https://mvnrepository.com/artifact/org.mapdb/mapdb![icon-default.png_t_M85B][]https://mvnrepository.com/artifact/org.mapdb/mapdb][https_mvnrepository.com_artifact_org.mapdb_mapdb_icon-default.png_t_M85B_https_mvnrepository.com_artifact_org.mapdb_mapdb]

MapDB用途多元化，MapDB提供拆箱即用的NoSQL键值数据存储模式。MapDB可以简单的基于内存、只在内存中内建数据库存储键值数据，当JVM关闭后所有数据自动消失。也可以将内存中的数据flush到本地一个文件中。总结起来，MapDB和一些常规的嵌入内存的NoSQL数据库相比，多出一个特点：**不仅可以嵌入内存的数据存取，也能将内存数据flush到本地文件持久化。**

下面一个例子，说明MapDB基于数据库文件存取内存数据.

pom.xml里面添加依赖：

<dependency>
                <groupId>org.mapdb</groupId>
                <artifactId>mapdb</artifactId>
                <version>3.0.8</version>
            </dependency>

Java代码：

import org.mapdb.DB;
    import org.mapdb.DBMaker;
    import org.mapdb.HTreeMap;
    import org.mapdb.Serializer;
    
    import java.util.concurrent.TimeUnit;
    
    public class MainClass {
        final String KEY = "name";
        final String MAP = "map";
    
        public MainClass() {
            write();
            read();
        }
    
        private void write() {
            DB db = DBMaker
                    .fileDB("./myfile.db")
                    .make();
    
            HTreeMap<String, String> map = db.hashMap(MAP)
                    .keySerializer(Serializer.STRING)
                    .valueSerializer(Serializer.STRING)
                    .expireAfterCreate(30, TimeUnit.SECONDS)
                    .createOrOpen();
    
            map.put(KEY, "zhangphil");
            System.out.println("write ok");
            System.out.println("-----");
            db.commit();
    
            db.close();
        }
    
        private void read() {
            DB db = DBMaker
                    .fileDB("./myfile.db")
                    .make();
    
            HTreeMap<String, String> map = db.hashMap(MAP)
                    .keySerializer(Serializer.STRING)
                    .valueSerializer(Serializer.STRING)
                    .expireAfterCreate(30, TimeUnit.SECONDS)
                    .createOrOpen();
    
            System.out.println(map.isEmpty());
            System.out.println(map.get(KEY));
    
            db.close();
        }
    
    
        public static void main(String[] atgs) {
            new MainClass();
        }
    }

代码运行后，在工程项目下生成一个数据库文件myfile.db：

![3eac9ea6724a430e8d3f66ba1f7c5234.png][]

输出：

> write ok  
> \-----  
> false  
> zhangphil

[fluidicon.png]: https://github.com/fluidicon.png
[GitHub - jankotek_mapdb_ MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine. - GitHub - jankotek_mapdb_ MapDB provides concurrent Maps_ Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine._fluidicon.png_https_github.com_jankotek_mapdb]: https://github.com/jankotek/mapdb
[icon-default.png_t_M85B]: https://csdnimg.cn/release/blog_editor_html/release2.2.0/ckeditor/plugins/CsdnLink/icons/icon-default.png?t=M85B
[https_mvnrepository.com_artifact_org.mapdb_mapdb_icon-default.png_t_M85B_https_mvnrepository.com_artifact_org.mapdb_mapdb]: https://mvnrepository.com/artifact/org.mapdb/mapdb
[3eac9ea6724a430e8d3f66ba1f7c5234.png]: https://img-blog.csdnimg.cn/3eac9ea6724a430e8d3f66ba1f7c5234.png