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

java.lang.Object
  org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader<T>

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>

Direct Known Subclasses:

AbstractCursorItemReader, AbstractPagingItemReader, FlatFileItemReader, HibernateCursorItemReader, StaxEventItemReader

public abstract class AbstractItemCountingItemStreamItemReader<T>
extends Object
implements ItemStreamReader<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

Constructor Summary

AbstractItemCountingItemStreamItemReader()

Method Summary

void	close() 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 T	doRead() Read next item from input.
protected int	getCurrentItemCount()
protected ExecutionContextUserSupport	getExecutionContextUserSupport()
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) Open the stream for the provided ExecutionContext.
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	setName(String name) The name of the component which will be used as a stem for keys in the ExecutionContext.
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

AbstractItemCountingItemStreamItemReader

public AbstractItemCountingItemStreamItemReader()

Method Detail

doRead

protected abstract T 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 final T read()
             throws 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.

Specified by:

read in interface ItemReader<T>

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.

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:

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

See Also:

setName(String)

close

public void close()
           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

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

getExecutionContextUserSupport

protected ExecutionContextUserSupport getExecutionContextUserSupport()

setName

public void setName(String name)

The name of the component which will be used as a stem for keys in the ExecutionContext. Subclasses should provide a default value, e.g. the short form of the class name.

Parameters:

name - the name for the component

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