Package org.springframework.batch.item.file

Class MultiResourceItemReader<T>

java.lang.Object

org.springframework.batch.item.ItemStreamSupport

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

org.springframework.batch.item.file.MultiResourceItemReader<T>

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>

public class MultiResourceItemReader<T>
extends AbstractItemStreamItemReader<T>

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.

Author:

Robert Kasanicky, Lucas Ward, Mahmoud Ben Hassine

Constructor Summary

Constructors

Constructor	Description
MultiResourceItemReader()

Method Summary

Modifier and Type	Method	Description
void	close()	Close the setDelegate(ResourceAwareItemReaderItemStream) reader and reset instance variable values.
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.
T	read()	Reads the next item, jumping to next resource if necessary.
void	setComparator(Comparator<org.springframework.core.io.Resource> comparator)
void	setDelegate(ResourceAwareItemReaderItemStream<? extends T> delegate)
void	setResources(org.springframework.core.io.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	setStrict(boolean strict)	In strict mode the reader will throw an exception on open(org.springframework.batch.item.ExecutionContext) if there are no resources to read.
void	update(ExecutionContext executionContext)	Store the current resource index and position in the resource.

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

getExecutionContextKey, getName, setExecutionContextName, setName

Methods inherited from class java.lang.Object

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

Constructor Details

MultiResourceItemReader

public MultiResourceItemReader()

Method Details

setStrict

public void setStrict(boolean strict)

In strict mode the reader will throw an exception on open(org.springframework.batch.item.ExecutionContext) if there are no resources to read.

Parameters:

strict - false by default

read

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

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

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.

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

close

public void close()
           throws ItemStreamException

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

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

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

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

Store the current resource index and position in the resource.

Specified by:

update in interface ItemStream

Overrides:

update in class ItemStreamSupport

Parameters:

executionContext - to be updated

Throws:

ItemStreamException

See Also:

• ItemStream.update(ExecutionContext)

setDelegate

public void setDelegate(ResourceAwareItemReaderItemStream<? extends T> 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 - true to update ExecutionContext. False do not update ExecutionContext.

setComparator

public void setComparator(Comparator<org.springframework.core.io.Resource> comparator)

Parameters:

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

setResources

public void setResources(org.springframework.core.io.Resource[] resources)

Parameters:

resources - input resources