org.springframework.batch.item.support
Class AbstractBufferedItemReaderItemStream

java.lang.Object
  org.springframework.batch.item.support.AbstractBufferedItemReaderItemStream

All Implemented Interfaces:

ItemReader, ItemStream

Direct Known Subclasses:

FlatFileItemReader, HibernateCursorItemReader, JdbcCursorItemReader, StaxEventItemReader

public abstract class AbstractBufferedItemReaderItemStream
extends Object
implements ItemReader, ItemStream

Abstract superclass for ItemReaders which use item buffering to support reset/rollback. 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

Constructor Summary

AbstractBufferedItemReaderItemStream()

Method Summary

void	close(ExecutionContext executionContext) If any resources are needed for the stream to operate they need to be destroyed here.
protected abstract void	doClose() Close the resources opened in doOpen().
protected abstract void	doOpen() Open resources necessary to start reading input.
protected abstract Object	doRead() Read next item from input.
protected int	getCurrentItemCount()
protected void	jumpToItem(int itemIndex) Move to the given item index.
void	mark() Mark is supported as long as this ItemStream is used in a single-threaded environment.
void	open(ExecutionContext executionContext) Open the stream for the provided ExecutionContext.
Object	read() Reads a piece of input data and advance to the next one.
void	reset() Reset the stream to the last mark.
protected void	setCurrentItemCount(int count)
void	setName(String name)
void	setSaveState(boolean saveState) Set the flag that determines whether to save internal data for ExecutionContext.
void	update(ExecutionContext executionContext) Indicates that the execution context provided during open is about to be saved.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractBufferedItemReaderItemStream

public AbstractBufferedItemReaderItemStream()

Method Detail

doRead

protected abstract Object doRead()
                          throws Exception

Read next item from input.

Returns:

item

Throws:

Exception

doOpen

protected abstract void doOpen()
                        throws Exception

Open resources necessary to start reading input.

Throws:

Exception

doClose

protected abstract void doClose()
                         throws Exception

Close the resources opened in doOpen().

Throws:

Exception

jumpToItem

protected void jumpToItem(int itemIndex)
                   throws 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().

Throws:

Exception

read

public Object read()
            throws Exception,
                   UnexpectedInputException,
                   NoWorkFoundException,
                   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.

Specified by:

read in interface ItemReader

Throws:

Exception - if an underlying resource is unavailable.

UnexpectedInputException

NoWorkFoundException

ParseException

mark

public void mark()
          throws MarkFailedException

Mark is supported as long as this ItemStream is used in a single-threaded environment. The state backing the mark is a single counter, keeping track of the current position, so multiple threads cannot be accommodated.

Specified by:

mark in interface ItemReader

Throws:

MarkFailedException - if there is a problem with the mark. If a mark fails inside a transaction, it would be worrying, but not normally fatal.

See Also:

AbstractItemReader.mark()

reset

public void reset()
           throws ResetFailedException

Description copied from interface: ItemReader

Reset the stream to the last mark. After a reset the stream state will be such that changes (items read or written) since the last call to mark will not be visible after a call to close.

Specified by:

reset in interface ItemReader

Throws:

ResetFailedException - if there is a problem with the reset. If a reset fails inside a transaction, it would normally be fatal, and would leave the stream in an inconsistent state. So while this is an unchecked exception, it may be important for a client to catch it explicitly.

getCurrentItemCount

protected int getCurrentItemCount()

setCurrentItemCount

protected void setCurrentItemCount(int count)

close

public void close(ExecutionContext executionContext)
           throws ItemStreamException

Description copied from interface: ItemStream

If any resources are needed for the stream to operate they need to be destroyed here. Once this method has been called all other methods (except open) may throw an exception.

Specified by:

close in interface ItemStream

Parameters:

executionContext - the current execution context in case it is needed

Throws:

ItemStreamException

open

public void open(ExecutionContext executionContext)
          throws ItemStreamException

Description copied from interface: ItemStream

Open the stream for the provided ExecutionContext.

Specified by:

open in interface ItemStream

Throws:

ItemStreamException

update

public void update(ExecutionContext executionContext)
            throws ItemStreamException

Description copied from interface: ItemStream

Indicates that the execution context provided during open is about to be saved. If any state is remaining, but has not been put in the context, it should be added here.

Specified by:

update in interface ItemStream

Parameters:

executionContext - to be updated

Throws:

ItemStreamException

setName

public void setName(String name)

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.

Parameters:

saveState - flag value (default true).