Package org.springframework.batch.infrastructure.item.support

Class CompositeItemReader<T>

java.lang.Object

org.springframework.batch.infrastructure.item.support.CompositeItemReader<T>

Type Parameters:

T - type of objects to read

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>

public class CompositeItemReader<T>
extends Object
implements ItemStreamReader<T>

Composite reader that delegates reading to a list of ItemStreamReaders. This implementation is not thread-safe.

Since:

5.2

Author:

Mahmoud Ben Hassine, Elimelec Burghelea

Constructor Summary

Constructors

Constructor	Description
CompositeItemReader(List<ItemStreamReader<? extends T>> delegates)	Create a new CompositeItemReader.

Method Summary

Modifier and Type	Method	Description
void	close()	Close all delegates.
void	open(ExecutionContext executionContext)	Open the stream for the provided ExecutionContext.
@Nullable T	read()	Reads a piece of input data and advance to the next one.
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 Details

CompositeItemReader

public CompositeItemReader(List<ItemStreamReader<? extends T>> delegates)

Create a new CompositeItemReader.

Parameters:

delegates - the delegate readers to read data

Method Details

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

Parameters:

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

Throws:

ItemStreamException

read

public @Nullable T read()
                 throws Exception

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>

Returns:

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

Throws:

Exception - if an error occurs.

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

close

public void close()
           throws ItemStreamException

Close all delegates.

Specified by:

close in interface ItemStream

Throws:

ItemStreamException - thrown if one of the delegates fails to close. Original exceptions thrown by delegates are added as suppressed exceptions into this one, in the same order as delegates were registered.