Class KeyValueItemWriter<K,V>

java.lang.Object

org.springframework.batch.infrastructure.item.KeyValueItemWriter<K,V>

All Implemented Interfaces:

ItemWriter<V>, org.springframework.beans.factory.InitializingBean

Direct Known Subclasses:

KafkaItemWriter, RedisItemWriter

public abstract class KeyValueItemWriter<K,V>
extends Object
implements ItemWriter<V>, org.springframework.beans.factory.InitializingBean

A base class to implement any ItemWriter that writes to a key value store using a Converter to derive a key from an item. If a derived key is null, the item will be skipped and a warning logged.

Since:

2.2

Author:

David Turanski, Mahmoud Ben Hassine, Stefano Cordio

Field Summary

Fields

Modifier and Type	Field	Description
protected boolean	delete
protected org.springframework.core.convert.converter.Converter<V,K>	itemKeyMapper

Constructor Summary

Constructors

Constructor	Description
KeyValueItemWriter(org.springframework.core.convert.converter.Converter<V,K> itemKeyMapper)	Create a new KeyValueItemWriter instance.

Method Summary

Modifier and Type	Method	Description
void	afterPropertiesSet()
protected void	flush()	Flush items to the key/value store.
protected abstract void	init()	afterPropertiesSet() hook
void	setDelete(boolean delete)	Sets the delete flag to have the item writer perform deletes
void	setItemKeyMapper(org.springframework.core.convert.converter.Converter<V,K> itemKeyMapper)	Set the Converter to use to derive the key from the item
void	write(Chunk<? extends V> chunk)	Process the supplied data element.
protected abstract void	writeKeyValue(K key, V value)	Subclasses implement this method to write each item to key value store

Methods inherited from class Object

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

Field Details

itemKeyMapper

protected org.springframework.core.convert.converter.Converter<V,K> itemKeyMapper

delete

protected boolean delete

Constructor Details

KeyValueItemWriter

public KeyValueItemWriter(org.springframework.core.convert.converter.Converter<V,K> itemKeyMapper)

Create a new KeyValueItemWriter instance.

Parameters:

itemKeyMapper - the Converter used to derive a key from an item.

Since:

6.0

Method Details

write

public void write(Chunk<? extends V> chunk)
           throws Exception

Description copied from interface: ItemWriter

Process the supplied data element. Will not be called with any null items in normal operation but might be called with an empty chunk, for example when all items have been filtered by an ItemProcessor or skipped by the fault-tolerant step processing. Implementations are expected to handle empty chunks gracefully.

Specified by:

write in interface ItemWriter<K>

Parameters:

chunk - of items to be written. Never null but may be empty.

Throws:

Exception - if there are errors. The framework will catch the exception and convert or rethrow it as appropriate.

flush

protected void flush()
              throws Exception

Flush items to the key/value store.

Throws:

Exception - if unable to flush items

writeKeyValue

protected abstract void writeKeyValue(K key,
 V value)

Subclasses implement this method to write each item to key value store

Parameters:

key - the key

value - the item

init

protected abstract void init()

afterPropertiesSet() hook

setItemKeyMapper

public void setItemKeyMapper(org.springframework.core.convert.converter.Converter<V,K> itemKeyMapper)

Set the Converter to use to derive the key from the item

Parameters:

itemKeyMapper - the Converter used to derive a key from an item.

setDelete

public void setDelete(boolean delete)

Sets the delete flag to have the item writer perform deletes

Parameters:

delete - if true ItemWriter will perform deletes, if false not to perform deletes.

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Specified by:

afterPropertiesSet in interface org.springframework.beans.factory.InitializingBean

Throws:

Exception