NoSQL Archives - CoderPanda

We already discussed the fundamentals of Apache Cassandra . We also discussed the fundamental operations like insert , read and delete with Apache Cassandra using Apache Hector as the client.In this chapter we are discussing how a CQL Select Query is working with Apache Cassandra with Hector API as the high level client.

CQL Select Query example in Java

We already created a key space ‘USERKEYSPACE‘ earlier.And we created a column family ‘userColumnFamily‘ and we inserted few data into it .(Explained in a previous post). In this chapter we are retrieving the same piece of data we inserted there by running a CQL select query from our Java application.

Before starting the coding , the Apache Cassandra should be started and the necessary libraries should be put in the work space as explained in the previous discussion.Now the ‘userColumnFamily‘ contains the following data(After insertion).

CqlReadSample.java

import me.prettyprint.cassandra.model.CqlQuery; import me.prettyprint.cassandra.model.CqlRows; import me.prettyprint.cassandra.model.RowImpl; import me.prettyprint.cassandra.serializers.StringSerializer; import me.prettyprint.hector.api.Cluster; import me.prettyprint.hector.api.Keyspace; import me.prettyprint.hector.api.beans.HColumn; import me.prettyprint.hector.api.factory.HFactory; import me.prettyprint.hector.api.query.QueryResult;


public class CqlReadSample {

    Cluster cluster = null;

    Keyspace keySpace = null;
    public CqlReadSample() {
    }
    public void getConfig() {

        cluster = HFactory.getOrCreateCluster("Test Cluster", "localHost:9160");

        keySpace = HFactory.createKeyspace("USERKEYSPACE", cluster);

    }
    public void read() {

        if (null != cluster && null != keySpace) {

            CqlQuery cqlQuery = new CqlQuery(

                    keySpace, StringSerializer.get(), StringSerializer.get(),

                    StringSerializer.get());

            cqlQuery.setQuery("select * from userColumnFamily");

            QueryResult> result = cqlQuery

                    .execute();

            CqlRows rows = result.get();

            for (int i = 0; i < rows.getCount(); i++) {
                RowImpl row = (RowImpl) rows

                        .getList().get(i);

                System.out.println("Row key = " + row.getKey());

                for (HColumn column : row.getColumnSlice()

                        .getColumns()) {

                    System.out.println("Column name = "

                            + column.getName().toString());

                    System.out.println("Colmn value = "

                            + column.getValue().toString());

                }

            }
        }

    }

    public static void main(String[] args) {

        CqlReadSample sample = new CqlReadSample();

        sample.getConfig();

        sample.read();

    }