org.springframework.batch.item.support

Class AbstractItemCountingItemStreamItemReader<T>

java.lang.Object

org.springframework.batch.item.ItemStreamSupport

org.springframework.batch.item.support.AbstractItemStreamItemReader<T>

org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader<T>

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>

Direct Known Subclasses:

AbstractCursorItemReader, AbstractPaginatedDataItemReader, AbstractPagingItemReader, AvroItemReader, FlatFileItemReader, HibernateCursorItemReader, JsonItemReader, LdifReader, MappingLdifReader, RepositoryItemReader, StaxEventItemReader

public abstract class AbstractItemCountingItemStreamItemReader<T>
extends AbstractItemStreamItemReader<T>

Abstract superclass for ItemReaders that supports restart by storing item count in the ExecutionContext (therefore requires item ordering to be preserved between runs). Subclasses are inherently not thread-safe.

Author:

Robert Kasanicky, Glenn Renfro, Mahmoud Ben Hassine

Constructor Summary

Constructors

Constructor and Description
AbstractItemCountingItemStreamItemReader()

Method Summary

Modifier and Type	Method and Description
void	close() No-op.
protected abstract void	doClose() Close the resources opened in doOpen().
protected abstract void	doOpen() Open resources necessary to start reading input.
protected abstract T	doRead() Read next item from input.
protected int	getCurrentItemCount()
boolean	isSaveState() The flag that determines whether to save internal state for restarts.
protected void	jumpToItem(int itemIndex) Move to the given item index.
void	open(ExecutionContext executionContext) No-op.
T	read() Reads a piece of input data and advance to the next one.
void	setCurrentItemCount(int count) The index of the item to start reading from.
void	setMaxItemCount(int count) The maximum index of the items to be read.
void	setSaveState(boolean saveState) Set the flag that determines whether to save internal data for ExecutionContext.
void	update(ExecutionContext executionContext) Return empty ExecutionContext.

Methods inherited from class org.springframework.batch.item.ItemStreamSupport

getExecutionContextKey, setExecutionContextName, setName

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractItemCountingItemStreamItemReader

public AbstractItemCountingItemStreamItemReader()

Method Detail

doRead

@Nullable
protected abstract T doRead()
                               throws java.lang.Exception

Read next item from input.

Returns:

an item or null if the data source is exhausted

Throws:

java.lang.Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

doOpen

protected abstract void doOpen()
                        throws java.lang.Exception

Open resources necessary to start reading input.

Throws:

java.lang.Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

doClose

protected abstract void doClose()
                         throws java.lang.Exception

Close the resources opened in doOpen().

Throws:

java.lang.Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

jumpToItem

protected void jumpToItem(int itemIndex)
                   throws java.lang.Exception

Move to the given item index. Subclasses should override this method if there is a more efficient way of moving to given index than re-reading the input using doRead().

Parameters:

itemIndex - index of item (0 based) to jump to.

Throws:

java.lang.Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

read

@Nullable
public T read()
                 throws java.lang.Exception,
                        UnexpectedInputException,
                        ParseException

Description copied from interface: ItemReader

Reads a piece of input data and advance to the next one. Implementations must return null at the end of the input data set. In a transactional setting, caller might get the same item twice from successive calls (or otherwise), if the first call was in a transaction that rolled back.

Returns:

T the item to be processed or null if the data source is exhausted

Throws:

ParseException - if there is a problem parsing the current record (but the next one may still be valid)

NonTransientResourceException - if there is a fatal exception in the underlying resource. After throwing this exception implementations should endeavour to return null from subsequent calls to read.

UnexpectedInputException - if there is an uncategorised problem with the input data. Assume potentially transient, so subsequent calls to read might succeed.

java.lang.Exception - if an there is a non-specific error.

getCurrentItemCount

protected int getCurrentItemCount()

setCurrentItemCount

public void setCurrentItemCount(int count)

The index of the item to start reading from. If the ExecutionContext contains a key [name].read.count (where [name] is the name of this component) the value from the ExecutionContext will be used in preference.

Parameters:

count - the value of the current item count

See Also:

ItemStreamSupport.setName(String)

setMaxItemCount

public void setMaxItemCount(int count)

The maximum index of the items to be read. If the ExecutionContext contains a key [name].read.count.max (where [name] is the name of this component) the value from the ExecutionContext will be used in preference.

Parameters:

count - the value of the maximum item count. count must be greater than zero.

See Also:

ItemStreamSupport.setName(String)

close

public void close()
           throws ItemStreamException

Description copied from class: ItemStreamSupport

No-op.

Specified by:

close in interface ItemStream

Overrides:

close in class ItemStreamSupport

Throws:

ItemStreamException

See Also:

ItemStream.close()

open

public void open(ExecutionContext executionContext)
          throws ItemStreamException

Description copied from class: ItemStreamSupport

No-op.

Specified by:

open in interface ItemStream

Overrides:

open in class ItemStreamSupport

Parameters:

executionContext - current step's ExecutionContext. Will be the executionContext from the last run of the step on a restart.

Throws:

ItemStreamException

See Also:

ItemStream.open(ExecutionContext)

update

public void update(ExecutionContext executionContext)
            throws ItemStreamException

Description copied from class: ItemStreamSupport

Return empty ExecutionContext.

Specified by:

update in interface ItemStream

Overrides:

update in class ItemStreamSupport

Parameters:

executionContext - to be updated

Throws:

ItemStreamException

See Also:

ItemStream.update(ExecutionContext)

setSaveState

public void setSaveState(boolean saveState)

Set the flag that determines whether to save internal data for ExecutionContext. Only switch this to false if you don't want to save any state from this stream, and you don't need it to be restartable. Always set it to false if the reader is being used in a concurrent environment.

Parameters:

saveState - flag value (default true).

isSaveState

public boolean isSaveState()

The flag that determines whether to save internal state for restarts.

Returns:

true if the flag was set