DataBase

We already discussed the fundamental concepts of Apache Cassandra database.We  discussed the basic operations with Apache Cassandra from Java. Those operations are read, insert , delete etc. In this chapter we are discussing how a Java object is persisting in Apache Cassandra . Here, we are   simply putting  all the attribute values of an object against the attribute names in a column family. Each object can be identified with a unique row key.

Inserting Objects into Apache Cassandra using Hector API

Apache Thrift allows us to generate classes to easily communicate with Apache Cassandra from client applications. Let us see an example. This example generates a class Student with two attributes ‘id‘ and ‘name‘.

Generating class using Thrift

The steps are :

1)Download Thrift.exe from Apache Page. 

(We are using Thrift 0.9.0 because we are using Thrift libraries 0.9.0 to communicate with Apache Cassandra)

2)Create a directory some where in disk and put the Thrift.exe in it.

(In our case , I created a folder Thrift in D drive)

3)Now create a file with .Thrift extension in the directory created in step 2.

(In our case the file is beans.Thrift)

4)Now put the following as content of beans.Thrift.

#namespace defines package for generated classes

namespace java com.cassandrasamples.beans

struct Student{

1:string id,

2:string name

}

The name space specifies the language and the package 

5)Now open a command prompt and go to the thrift directory and execute the command :

thrift-0.9.0.exe -gen java beans.thrift

This generates a class with already mentioned package in the gen-java folder inside thrift directory.

Put the generated class in the corresponding package in  work space . In the coming example , we will be using this as a model class.(I am not copying the generated class here.)

Now let us look into the Java client application which inserts few Student objects into Apache Cassandra database. We are using the same key space ‘USERKEYSPACE‘ created already .We  need to start Apache Cassandra database and we should include the libraries mentioned there   to the work space to run our application.

ObjectInsertSample.java

The Student object has ‘id’ and ‘name’ . We are storing two Student objects in a new column family ‘myColumnFamily‘.Each object is having a unique row key . The  Student id is using as row  key.

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import me.prettyprint.cassandra.serializers.StringSerializer;
import me.prettyprint.hector.api.Cluster;
import me.prettyprint.hector.api.Keyspace;
import me.prettyprint.hector.api.ddl.ColumnFamilyDefinition;
import me.prettyprint.hector.api.ddl.ComparatorType;
import me.prettyprint.hector.api.factory.HFactory;
import me.prettyprint.hector.api.mutation.Mutator;

import com.cassandrasamples.beans.Student;

public class ObjectInsertSample {
Cluster cluster = null;
Keyspace keyspace = null;

public ObjectInsertSample() {

}

public void getConfig() {
cluster = HFactory.getOrCreateCluster("Test Cluster", "localHost:9160");
keyspace = HFactory.createKeyspace("USERKEYSPACE", cluster);
}

public void insert(List studentList) {
if (null != cluster && null != keyspace) {
ColumnFamilyDefinition columnFamily = HFactory
.createColumnFamilyDefinition("USERKEYSPACE",
"myColumnFamily", ComparatorType.UTF8TYPE);
cluster.addColumnFamily(columnFamily);
StringSerializer stringSerializer = StringSerializer.get();
Mutator mutator = HFactory.createMutator(keyspace,
stringSerializer);
for (Student student : studentList) {
Map map = processKeyValueMap(student);
Set set = map.entrySet();
Iterator i = set.iterator();
while (i.hasNext()) {

Map.Entry entry = (Map.Entry) i.next();
mutator.addInsertion(student.getId(), columnFamily
.getName(), HFactory.createStringColumn(entry
.getKey().toString(), entry.getValue().toString()));
System.out.println("Done");
}
mutator.execute();

}
}
}

public Map processKeyValueMap(Student student) {
HashMap returnMap = new HashMap();
if (null != student.getId() && null != student.getName()) {
returnMap.put("id", student.getId());
returnMap.put("name", student.getName());

}
return returnMap;

}

public static void main(String[] args) {
ObjectInsertSample sample = new ObjectInsertSample();
sample.getConfig();
Student student1 = new Student();
student1.setId("1");
student1.setName("Bijoy");
Student student2 = new Student();
student2.setId("2");
student2.setName("Karthik");
List students = new ArrayList();
students.add(student1);
students.add(student2);
System.out.println("Inserting student records....");
sample.insert(students);
System.out.println("Done...");

}
}


After insertion the column family structure will be  like this:

Output

We need to start the Apache Cassandra database and the key space ‘USERKEYSPACE’ should be added as discusses earlier.We should include the libraries discussed there.Now run the application. When insertion is successful , corresponding messages will be displayed .In the next chapter we’ll see how these data is retrieving.

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

Reading objects from Apache Cassandra