ScyllaDB Docs ScyllaDB Cloud Getting Started Documentation Quick start: Java

Quick start: Java¶

In this tutorial you’ll build a Media Player to store your songs and build playlists.

1. Getting the Driver¶

Add the ScyllaDB Java Driver to your pom.xml:

<dependency>
  <groupId>com.scylladb</groupId>
  <artifactId>java-driver-core</artifactId>
  <version>4.18.0.0</version>
</dependency>

To package your application as a fat JAR (all dependencies included), use the maven-shade-plugin:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <version>3.5.1</version>
  <executions>
    <execution>
      <phase>package</phase>
      <goals><goal>shade</goal></goals>
      <configuration>
        <outputFile>${project.build.directory}/app.jar</outputFile>
        <transformers>
          <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
            <mainClass>com.scylladb.App</mainClass>
          </transformer>
          <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
          <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
            <resource>reference.conf</resource>
          </transformer>
        </transformers>
      </configuration>
    </execution>
  </executions>
</plugin>

2. Connecting to the cluster¶

Get your database credentials from your ScyllaDB Cloud Cluster View in the tab Connect.

Add your machine’s IP Address to the list of allowed IP addresses in ScyllaDB Cloud. Otherwise, your connection will get refused.

import com.datastax.oss.driver.api.core.CqlSession;
import java.net.InetSocketAddress;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();
    }
}

3. Handling Queries¶

With the ScyllaDB Java driver 4.x, use session.execute(query) to run CQL statements.

import com.datastax.oss.driver.api.core.CqlSession;
import com.datastax.oss.driver.api.core.cql.ResultSet;
import com.datastax.oss.driver.api.core.cql.Row;
import java.net.InetSocketAddress;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        ResultSet result = session.execute("SELECT * FROM system.clients LIMIT 10");
        for (Row row : result) {
            System.out.println(row.toString());
        }

        session.close();
    }
}

3.1 Create a keyspace¶

A keyspace in ScyllaDB is a collection of tables with attributes which define how data is replicated on nodes.

import com.datastax.oss.driver.api.core.CqlSession;
import java.net.InetSocketAddress;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        session.execute(
            "CREATE KEYSPACE IF NOT EXISTS media_player " +
            "WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': '3'} " +
            "AND durable_writes = true"
        );

        session.close();
    }
}

3.2 Create table¶

A table stores part or all of your app data (depending on how you structure your database schema). Add the keyspace prefix in your table name and define a CQL string that creates a table to store your favorite songs.

import com.datastax.oss.driver.api.core.CqlSession;
import java.net.InetSocketAddress;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        session.execute(
            "CREATE TABLE IF NOT EXISTS media_player.playlist (" +
            "  id uuid," +
            "  title text," +
            "  album text," +
            "  artist text," +
            "  created_at timestamp," +
            "  PRIMARY KEY (id, created_at)" +
            ") WITH CLUSTERING ORDER BY (created_at DESC)"
        );

        session.close();
    }
}

3.3 Insert data¶

Now that you have created a keyspace and a table, insert some songs to populate the table.

import com.datastax.oss.driver.api.core.CqlSession;
import com.datastax.oss.driver.api.core.cql.PreparedStatement;
import java.net.InetSocketAddress;
import java.time.Instant;
import java.util.UUID;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        PreparedStatement ps = session.prepare(
            "INSERT INTO media_player.playlist (id, title, artist, album, created_at) VALUES (?, ?, ?, ?, ?)"
        );

        session.execute(ps.bind(
            UUID.randomUUID(),
            "Stairway to Heaven",
            "Led Zeppelin",
            "Led Zeppelin IV",
            Instant.now()
        ));

        session.close();
    }
}

3.4 Read data¶

Let’s read the songs from the database and print them to the terminal.

import com.datastax.oss.driver.api.core.CqlSession;
import com.datastax.oss.driver.api.core.cql.ResultSet;
import com.datastax.oss.driver.api.core.cql.Row;
import java.net.InetSocketAddress;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        ResultSet rs = session.execute(
            "SELECT id, title, album, artist, created_at FROM media_player.playlist PER PARTITION LIMIT 1 LIMIT 100"
        );

        for (Row row : rs) {
            System.out.printf(
                "ID: %s -> Song: %s -> Artist: %s -> Album: %s -> Created At: %s%n",
                row.getUuid("id"),
                row.getString("title"),
                row.getString("artist"),
                row.getString("album"),
                row.getInstant("created_at")
            );
        }

        session.close();
    }
}

3.5 Update data¶

The UPDATE query takes two fields in the WHERE clause (partition key and clustering key). See the snippet below:

import com.datastax.oss.driver.api.core.CqlSession;
import com.datastax.oss.driver.api.core.cql.PreparedStatement;
import java.net.InetSocketAddress;
import java.time.Instant;
import java.util.UUID;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        UUID songId = UUID.fromString("d754f8d5-e037-4898-af75-44587b9cc424");

        PreparedStatement ps = session.prepare(
            "UPDATE media_player.song_counter SET times_played = times_played + 1 WHERE song_id = ?"
        );

        session.execute(ps.bind(songId));

        session.close();
    }
}

After the data gets inserted, query all columns and filter by the ID:

scylla@cqlsh:media_player> select * from playlist where id = d754f8d5-e037-4898-af75-44587b9cc424;

 id                                   | created_at                      | album           | artist      | title
--------------------------------------+---------------------------------+-----------------+-------------+------------------
 d754f8d5-e037-4898-af75-44587b9cc424 | 2023-03-02 22:00:00.000000+0000 | Led Zeppelin IV | Led Zeppelin | Stairway to Heaven

3.6 Delete Data¶

Last things last! Let’s understand what we can DELETE with this statement. There’s the regular DELETE statement that focuses on ROWS and the other one that deletes data only from COLUMNS. The syntax is very similar.

-- Deletes all rows for a partition
DELETE FROM media_player.playlist WHERE id = d754f8d5-e037-4898-af75-44587b9cc424;

-- Deletes a specific cell
DELETE artist FROM media_player.playlist WHERE id = d754f8d5-e037-4898-af75-44587b9cc424 AND created_at = '2023-03-02 22:00:00+0000';

If you want to remove a specific column, you also should pass the Clustering Key as parameter and be specific about which row you want to delete something from. On the other hand, deleting by partition key only will delete ALL the rows stored with that ID.

import com.datastax.oss.driver.api.core.CqlSession;
import com.datastax.oss.driver.api.core.cql.PreparedStatement;
import java.net.InetSocketAddress;
import java.util.UUID;

public class App {
    public static void main(String[] args) {
        CqlSession session = CqlSession.builder()
            .addContactPoint(new InetSocketAddress("node-0.aws-us-east-1.xxxx.clusters.scylla.cloud", 9042))
            .withAuthCredentials("scylla", "your-awesome-password")
            .withLocalDatacenter("AWS_US_EAST_1")
            .build();

        UUID songId = UUID.fromString("d754f8d5-e037-4898-af75-44587b9cc424");

        PreparedStatement ps = session.prepare(
            "DELETE FROM media_player.playlist WHERE id = ?"
        );

        session.execute(ps.bind(songId));

        session.close();
    }
}

Conclusion¶

Yay! You now know how to get started with ScyllaDB in Java.

There is a simple project with this structure that you can check out here.

If you think something can be improved, please open an issue and let’s make it happen!

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