org.jberet.support.io

Class CassandraItemReader

java.lang.Object

org.jberet.support.io.CassandraReaderWriterBase

org.jberet.support.io.CassandraItemReader

All Implemented Interfaces:

javax.batch.api.chunk.ItemReader

@Named
 @Dependent
public class CassandraItemReader
extends CassandraReaderWriterBase
implements javax.batch.api.chunk.ItemReader

An implementation of javax.batch.api.chunk.ItemReader that reads data items from the Cassandra cluster.

Since:

1.3.0

See Also:

CassandraItemWriter, CassandraBatchlet, CassandraReaderWriterBase

Field Summary

Fields

Modifier and Type	Field and Description
protected com.datastax.driver.core.ColumnDefinitions	columnDefinitions The column definitions of the ResultSet
protected String[]	columnLabels The column names of the ResultSet
protected String[]	columnMapping String keys used in target data structure for database columns.
protected int	currentRowNumber The current row number.
protected int	end The row number in the ResultSet to end reading (inclusive).
protected Integer	fetchSize The query fetch size.
protected Map<String,PropertyDescriptor>	propertyDescriptorMap For CassandraReaderWriterBase.beanType of custom POJO bean, this property defines a mapping between POJO bean's property name and its JavaBeans java.beans.PropertyDescriptor.
protected com.datastax.driver.core.ResultSet	resultSet The com.datastax.driver.core.ResultSet from executing statement
protected Iterator<com.datastax.driver.core.Row>	rowIterator The iterator of com.datastax.driver.core.Row based on resultSet
protected boolean	skipBeanValidation Whether to perform bean validation with Bean Validation API, if the CassandraReaderWriterBase.beanType is a custom POJO bean type.
protected int	start The row number in the ResultSet to start reading.
protected com.datastax.driver.core.Statement	statement The regular cql statement based on CassandraReaderWriterBase.cql

Fields inherited from class org.jberet.support.io.CassandraReaderWriterBase

beanType, cluster, clusterInstance, clusterProperties, contactPoints, cql, customCodecList, customCodecs, keyspace, password, propertyDescriptors, session, sessionCreated, sessionInstance, user

Constructor Summary

Constructors

Constructor and Description
CassandraItemReader()

Method Summary

Modifier and Type	Method and Description
Serializable	checkpointInfo()
protected void	initBeanPropertyDescriptors()
void	open(Serializable checkpoint)
Object	readItem()

Methods inherited from class org.jberet.support.io.CassandraReaderWriterBase

applyClusterProperties, close, initCustomCodecs, initSession

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.batch.api.chunk.ItemReader

close

Field Detail

start

@Inject
protected int start

The row number in the ResultSet to start reading. It's a positive integer starting from 1.

end

@Inject
protected int end

The row number in the ResultSet to end reading (inclusive). It's a positive integer starting from 1.

fetchSize

@Inject
protected Integer fetchSize

The query fetch size. As stated in com.datastax.driver.core.Statement#setFetchSize(int), the fetch size controls how much resulting rows will be retrieved simultaneously (the goal being to avoid loading too much results in memory for queries yielding large results). Please note that while value as low as 1 can be used, it is *highly* discouraged to use such a low value in practice as it will yield very poor performance. If in doubt, leaving the default is probably a good idea. Optional property, and defaults to null (not specified).

columnMapping

@Inject
protected String[] columnMapping

String keys used in target data structure for database columns. Optional property, and if not specified, it defaults to columnLabels.

For example, if CassandraReaderWriterBase.cql is

SELECT NAME, ADDRESS, AGE FROM PERSON

And you want to map the data to the following form:

{"fn" = "Jon", "addr" = "1 Main st", "age" = 30}

then columnMapping should be specified as follows in job xml:

"fn, addr, age"

skipBeanValidation

@Inject
protected boolean skipBeanValidation

Whether to perform bean validation with Bean Validation API, if the CassandraReaderWriterBase.beanType is a custom POJO bean type. Optional property, and defaults to false (perform bean validation).

columnLabels

protected String[] columnLabels

The column names of the ResultSet

statement

protected com.datastax.driver.core.Statement statement

The regular cql statement based on CassandraReaderWriterBase.cql

resultSet

protected com.datastax.driver.core.ResultSet resultSet

The com.datastax.driver.core.ResultSet from executing statement

rowIterator

protected Iterator<com.datastax.driver.core.Row> rowIterator

The iterator of com.datastax.driver.core.Row based on resultSet

columnDefinitions

protected com.datastax.driver.core.ColumnDefinitions columnDefinitions

The column definitions of the ResultSet

propertyDescriptorMap

protected Map<String,PropertyDescriptor> propertyDescriptorMap

For CassandraReaderWriterBase.beanType of custom POJO bean, this property defines a mapping between POJO bean's property name and its JavaBeans java.beans.PropertyDescriptor.

currentRowNumber

protected int currentRowNumber

The current row number.

Constructor Detail

CassandraItemReader

public CassandraItemReader()

Method Detail

open

public void open(Serializable checkpoint)
          throws Exception

Specified by:

open in interface javax.batch.api.chunk.ItemReader

Throws:

Exception

readItem

public Object readItem()
                throws Exception

Specified by:

readItem in interface javax.batch.api.chunk.ItemReader

Throws:

Exception

checkpointInfo

public Serializable checkpointInfo()
                            throws Exception

Specified by:

checkpointInfo in interface javax.batch.api.chunk.ItemReader

Throws:

Exception

initBeanPropertyDescriptors

protected void initBeanPropertyDescriptors()
                                    throws IntrospectionException

Overrides:

initBeanPropertyDescriptors in class CassandraReaderWriterBase

Throws:

IntrospectionException