Developing a Java app with Cassandra API using Azure Cosmos DB

Dernière mise à jour : 15/11/2017
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Azure Cosmos DB is a globally distributed multi-model database. One of the supported APIs is the Cassandra API. This sample walks you through creation of keyspace, table, inserting and querying the data.

Prerequisites

  • Before you can run this sample, you must have the following prerequisites:
    • An active Azure Cassandra API account - If you don't have an account, refer to the Create Cassandra API account.
    • Java Development Kit (JDK) 1.8+
      • On Ubuntu, run apt-get install default-jdk to install the JDK.
    • Be sure to set the JAVA_HOME environment variable to point to the folder where the JDK is installed.
    • Download and install a Maven binary archive
      • On Ubuntu, you can run apt-get install maven to install Maven.
    • Git
      • On Ubuntu, you can run sudo apt-get install git to install Git.

Running this sample

  1. Clone this repository using git clone git@github.com:Azure-Samples/azure-cosmos-db-cassandra-java-getting-started.git cosmosdb.

  2. Change directories to the repo using cd cosmosdb/java-examples

  3. Next, substitute the Cassandra host, username, password java-examples\src\main\resources\config.properties with your Cosmos DB account's values from connectionstring panel of the portal.

    cassandra_host=<FILLME>
    cassandra_username=<FILLME>
    cassandra_password=<FILLME>
    ssl_keystore_file_path=<FILLME>
    ssl_keystore_password=<FILLME>
    

    If ssl_keystore_file_path is not given in config.properties, then by default /jre/lib/security/cacerts will be used If ssl_keystore_password is not given in config.properties, then the default password 'changeit' will be used

  4. Run mvn clean install from java-examples folder to build the project. This will generate cosmosdb-cassandra-examples.jar under target folder.

  5. Run java -cp target/cosmosdb-cassandra-examples.jar com.azure.cosmosdb.cassandra.examples.UserProfile in a terminal to start your java application.

About the code

The code included in this sample is intended to get you quickly started with a Java console application that connects to Azure Cosmos DB with the Cassandra API.

Review the code

If you're interested in learning how the database resources are created in the code, you can review the following snippets. The snippets are all taken from src/main/java/com/azure/cosmosdb/cassandra/util/CassandraUtils.java and src/main/java/com/azure/cosmosdb/cassandra/repository/UserRepository.java files.

  • Cassandra Host, Port, User name and password is set using the connection string page in the Azure portal.
   this.cluster = Cluster.builder().addContactPoint(host).withPort(port).withCredentials(username, password).build();
  • The cluster connects to the Azure Cosmos DB Cassandra API and returns a session to access.

    return cluster.connect();
    
  • A new keyspace is created.

    public void createKeyspace() {
        final String query = "CREATE KEYSPACE IF NOT EXISTS uprofile WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'datacenter1' : 1 }";
        session.execute(query);
        LOGGER.info("Created keyspace 'uprofile'");
    }
    
  • A new table is created.

   public void createTable() {
        final String query = "CREATE TABLE IF NOT EXISTS uprofile.user (user_id int PRIMARY KEY, user_name text, user_bcity text)";
        session.execute(query);
        LOGGER.info("Created table 'user'");
   }
  • User entities are inserted using a prepared statement object.

    public PreparedStatement prepareInsertStatement() {
        final String insertStatement = "INSERT INTO  uprofile.user (user_id, user_name , user_bcity) VALUES (?,?,?)";
        return session.prepare(insertStatement);
    }
    
    public void insertUser(PreparedStatement statement, int id, String name, String city) {
        BoundStatement boundStatement = new BoundStatement(statement);
        session.execute(boundStatement.bind(id, name, city));
    }
    
  • Query to get get all User information.

    public void selectAllUsers() {
        final String query = "SELECT * FROM uprofile.user";
        List<Row> rows = session.execute(query).all();
    
        for (Row row : rows) {
            LOGGER.info("Obtained row: {} | {} | {} ", row.getInt("user_id"), row.getString("user_name"), row.getString("user_bcity"));
        }
    }
    
    • Query to get a single User information.
    public void selectUser(int id) {
        final String query = "SELECT * FROM uprofile.user where user_id = 3";
        Row row = session.execute(query).one();
    
        LOGGER.info("Obtained row: {} | {} | {} ", row.getInt("user_id"), row.getString("user_name"), row.getString("user_bcity"));
    }
    

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