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CQL Select Query example in Java

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 ‘USERKEYSPACEearlier.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();
}

}

Output

Row key = names

Column name = KEY

Colmn value = names

Column name = 1

Colmn value = Bijoy

Column name = 2

Colmn value = Karthik

Column name = 3

Colmn value = JayaKrishnan

See Related Posts:

Apache Cassandra overview

Configuring Apache Cassandra in local machine

Inserting data into Apache Cassandra using Java

Reading data from Apache Cassandra using Java

Listing columns in Apache Cassandra using Java

Deleting columns from Apache Cassandra using Java

Inserting object data into Apache Cassandra database

Reading object data from Apache Cassandra using Hector API

Updating object data in Apache Cassandra using Hector API