Develop Java Apps

Develop Java Apps

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Cassandra
Redis

Maven

To build your Java application using the YugabyteDB Cassandra driver, add the following Maven dependency to your application:

<dependency>
  <groupId>com.yugabyte</groupId>
  <artifactId>cassandra-driver-core</artifactId>
  <version>3.2.0-yb-12</version>
</dependency>

Working Example

Pre-requisites

This tutorial assumes that you have:

installed YugabyteDB, created a universe and are able to interact with it using the CQL shell. If not, please follow these steps in the quick start guide.
installed JDK version 1.8+ and maven 3.3+

Creating the maven build file

Create a maven build file pom.xml and add the following content into it.

<?xml version="1.0"?>
<project
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
  xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.yugabyte.sample.apps</groupId>
  <artifactId>hello-world</artifactId>
  <version>1.0</version>
  <packaging>jar</packaging>
  <dependencies>
    <dependency>
      <groupId>com.yugabyte</groupId>
      <artifactId>cassandra-driver-core</artifactId>
      <version>3.2.0-yb-12</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>2.1</version>
        <executions>
          <execution>
            <id>copy-dependencies</id>
            <phase>prepare-package</phase>
            <goals>
              <goal>copy-dependencies</goal>
            </goals>
            <configuration>
              <outputDirectory>${project.build.directory}/lib</outputDirectory>
              <overWriteReleases>true</overWriteReleases>
              <overWriteSnapshots>true</overWriteSnapshots>
              <overWriteIfNewer>true</overWriteIfNewer>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Writing a HelloWorld CQL app

Create the appropriate directory structure as expected by maven.

$ mkdir -p src/main/java/com/yugabyte/sample/apps

Copy the following contents into the file src/main/java/com/yugabyte/sample/apps/YBCqlHelloWorld.java.

package com.yugabyte.sample.apps;
import java.util.List;
import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
public class YBCqlHelloWorld {
  public static void main(String[] args) {
    try {
      // Create a Cassandra client.
      Cluster cluster = Cluster.builder()
                               .addContactPoint("127.0.0.1")
                               .build();
      Session session = cluster.connect();
      // Create keyspace 'ybdemo' if it does not exist.
      String createKeyspace = "CREATE KEYSPACE IF NOT EXISTS ybdemo;";
      ResultSet createKeyspaceResult = session.execute(createKeyspace);
      System.out.println("Created keyspace ybdemo");
      // Create table 'employee' if it does not exist.
      String createTable = "CREATE TABLE IF NOT EXISTS ybdemo.employee (id int PRIMARY KEY, " +
                                                                       "name varchar, " +
                                                                       "age int, " +
                                                                       "language varchar);";
      ResultSet createResult = session.execute(createTable);
      System.out.println("Created table employee");
      // Insert a row.
      String insert = "INSERT INTO ybdemo.employee (id, name, age, language)" +
                                          " VALUES (1, 'John', 35, 'Java');"; 
      ResultSet insertResult = session.execute(insert);
      System.out.println("Inserted data: " + insert);
      // Query the row and print out the result.
      String select = "SELECT name, age, language FROM ybdemo.employee WHERE id = 1;";
      ResultSet selectResult = session.execute(select);
      List<Row> rows = selectResult.all();
      String name = rows.get(0).getString(0);
      int age = rows.get(0).getInt(1);
      String language = rows.get(0).getString(2);
      System.out.println("Query returned " + rows.size() + " row: " +
                         "name=" + name + ", age=" + age + ", language: " + language);
      // Close the client.
      session.close();
      cluster.close();
    } catch (Exception e) {
        System.err.println("Error: " + e.getMessage());
    }
  }
}

Building and running the app

To build the application, just run the following command.

$ mvn package

To run the program, do the following.

$ java -cp "target/hello-world-1.0.jar:target/lib/*" com.yugabyte.sample.apps.YBCqlHelloWorld

You should see the following as the output.

Created keyspace ybdemo
Created table employee
Inserted data: INSERT INTO ybdemo.employee (id, name, age, language) VALUES (1, 'John', 35, 'Java');
Query returned 1 row: name=John, age=35, language: Java