JetstreamDB is a in-memory database engine for Java that claims to be built for ultra-high speed and the ability of managing complex data structures by storing real Java objects instead of serializing data structures to other database specific formats.
In the following short example I would like to demonstrate how to create and read items from such a database by building a small article management sample app.
Project Setup
First of all we’re adding some Maven repositories to our project’s pom.xml:
<repositories>
<repository>
<id>jetstream-releases</id>
<url>https://maven.jetstream.one/maven2-public</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
<repository>
<id>jetstream-snapshots</id>
<url>https://maven.jetstream.one/maven2-public-snapshot</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>Afterwards just need to add the following dependency:
<dependency>
<groupId>com.jetstreamdb</groupId>
<artifactId>jetstreamdb-embedded</artifactId>
<version>1.0.0-beta1</version>
</dependency>Sample Application
We’re now implementing a sample application to store and retreive some data from a jetstreamDB…
Root Entity
This is our aggregate, the root of our persisted data:
package com.hascode.tutorial;
import java.util.ArrayList;
import java.util.List;
public class RootData {
private final List<Article> articles = new ArrayList<>();
public List<Article> getArticles() {
return articles;
}
}Article Entity
This is our article entity
package com.hascode.tutorial;
public class Article {
private final String title;
// constructor, getter, setter, tostring ommitted..
}Command Line App
This is our command line app that allows us to create and list our articles:
package com.hascode.tutorial;
import com.jetstreamdb.JetstreamDBInstance;
import java.io.Console;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
public class ArticleApp {
private static final String USAGE = "Enter a command 'l': list, 'a': add, 'q': quit 'd': db info\n";
private JetstreamDBInstance<RootData> db;
public ArticleApp() {
db = JetstreamDBInstance.New("my-articles-db ", RootData.class);
Path databaseDirectory = Paths.get("").resolve("article-db");
System.out.printf("creating database directory in %s%n", databaseDirectory.toAbsolutePath());
db.configuration().properties().setStorageDirectory(databaseDirectory.toFile());
}
public static void main(String[] args) {
new ArticleApp().run();
}
public void run() {
prompt();
}
private void prompt() {
Console console = System.console();
System.out.println(USAGE);
String command = console.readLine();
switch (command) {
case "q":
System.out.println("quitting...");
System.exit(1);
break;
case "l":
List<Article> articles = db.root().getArticles();
System.out.printf("%d articles found:%n", articles.size());
articles.forEach(System.out::println);
prompt();
break;
case "a":
System.out.println("Please enter a title");
String title = console.readLine();
List<Article> update = db.root().getArticles();
update.add(new Article(title));
db.store(update);
prompt();
break;
case "d":
System.out.printf("basedir: %s, name: %s%n", db.configuration().getBaseDir(),
db.configuration().name());
prompt();
break;
default:
System.out.println("invalid command");
prompt();
}
}
}Running the Application
Now we’d like to add and fetch some data from our application:
We may start the application using our IDE or using Maven in the command line like this:
mvn clean compile exec:java -Dexec.mainClass=com.hascode.tutorial.ArticleApp
[..]
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ho /h: `sy`
hddd/oooooooooooooooo+omdo.
smmmoy+ d/dmmd/ JetstreamDB
-mmmm+h/ h/dmmmh
-mmmmh/y+` .oy+mmmmd Version 1.0.0-beta1
-mmmmdy.:os+-.```.:oso-:dmmmmd
:mh+- -yo. .:++o+/:``:so``/sdd
:h/ .+so+//:/+oss/` .oy.
:d. `` `.:m-.` `` /d.
h+ oo .d` +s so
d: oo .d` /oooo- +s +y
h/ oo .d` +s +y
/h----yo `: +y----h+
sd/::yo +y::/ds
:yo:so +s:oy/
./ho .d` oh/.
so .d` +y
oo .d` +y
ohoooo+++/+m+/+++oooohy
.ss+::/+shs/sho/:-:/ss.
``````````-:::-.`````-:///-`````````
````````````````````````````````````
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creating database directory in /data/project/jetstream-tutorial/article-db
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
l
0 articles found:
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
a
Please enter a title
Some title
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
l
1 articles found:
Article{title='Some title'}
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
d
basedir: article-db, name: my-articles-db
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
a
Please enter a title
another one
Enter a command 'l': list, 'a': add, 'q': quit 'd': db info
l
2 articles found:
Article{title='Some title'}
Article{title='another one'}
Enter a command 'l': list, 'a': add, 'q': quit 'd': db infoInternal Structure
Having created those articles we can see that jetstreamDB has created the following files in the designated directory:
/article-db
├── channel_0
│ ├── channel_0_1.dat
│ └── transactions_0.sft
├── ObjectId.oid
├── PersistenceTypeDictionary.ptd
└── TypeId.tidTutorial Sources
Please feel free to download the tutorial sources from my GitHub repository, fork it there or clone it using Git:
git clone https://github.com/hascode/jetstreamdb-tutorial.git