org.springframework.batch.item.file
Class MultiResourceItemReader

java.lang.Object
  org.springframework.batch.item.util.ExecutionContextUserSupport
      org.springframework.batch.item.file.MultiResourceItemReader

All Implemented Interfaces:

ItemReader, ItemStream

public class MultiResourceItemReader
extends ExecutionContextUserSupport
implements ItemReader, ItemStream

Reads items from multiple resources sequentially - resource list is given by setResources(Resource[]), the actual reading is delegated to setDelegate(ResourceAwareItemReaderItemStream). Input resources are ordered using setComparator(Comparator) to make sure resource ordering is preserved between job runs in restart scenario. Reset (rollback) capability is implemented by item buffering.

Author:

Robert Kasanicky

Constructor Summary

MultiResourceItemReader()

Method Summary

void	close(ExecutionContext executionContext) Close the setDelegate(ResourceAwareItemReaderItemStream) reader and reset instance variable values.
void	mark() Remove the longer needed items from buffer, mark the index position and call mark() on delegate so that it clears its buffers.
void	open(ExecutionContext executionContext) Figure out which resource to start with in case of restart, open the delegate and restore delegate's position in the resource.
Object	read() Reads the next item, jumping to next resource if necessary.
void	reset() Switches to 'read from buffer' state.
void	setComparator(Comparator comparator)
void	setDelegate(ResourceAwareItemReaderItemStream delegate)
void	setResources(Resource[] resources)
void	setSaveState(boolean saveState) Set the boolean indicating whether or not state should be saved in the provided ExecutionContext during the ItemStream call to update.
void	update(ExecutionContext executionContext) Store the current resource index and position in the resource.

Methods inherited from class org.springframework.batch.item.util.ExecutionContextUserSupport

getKey, setName

Methods inherited from class java.lang.Object

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

Constructor Detail

MultiResourceItemReader

public MultiResourceItemReader()

Method Detail

read

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

Reads the next item, jumping to next resource if necessary.

Specified by:

read in interface ItemReader

Throws:

Exception - if an underlying resource is unavailable.

UnexpectedInputException

NoWorkFoundException

ParseException

mark

public void mark()
          throws MarkFailedException

Remove the longer needed items from buffer, mark the index position and call mark() on delegate so that it clears its buffers.

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.

reset

public void reset()
           throws ResetFailedException

Switches to 'read from buffer' state.

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.

See Also:

ItemReader.reset()

close

public void close(ExecutionContext executionContext)
           throws ItemStreamException

Close the setDelegate(ResourceAwareItemReaderItemStream) reader and reset instance variable values.

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

Figure out which resource to start with in case of restart, open the delegate and restore delegate's position in the resource.

Specified by:

open in interface ItemStream

Throws:

ItemStreamException

update

public void update(ExecutionContext executionContext)
            throws ItemStreamException

Store the current resource index and position in the resource.

Specified by:

update in interface ItemStream

Parameters:

executionContext - to be updated

Throws:

ItemStreamException

setDelegate

public void setDelegate(ResourceAwareItemReaderItemStream delegate)

Parameters:

delegate - reads items from single Resource.

setSaveState

public void setSaveState(boolean saveState)

Set the boolean indicating whether or not state should be saved in the provided ExecutionContext during the ItemStream call to update.

Parameters:

saveState -

setComparator

public void setComparator(Comparator comparator)

Parameters:

comparator - used to order the injected resources, by default compares Resource.getFilename() values.

setResources

public void setResources(Resource[] resources)

Parameters:

resources - input resources