javax.batch.api.chunk
Interface ItemReader<T>

Type Parameters:

T - specifies the item type returned by this reader.

All Known Implementing Classes:

AbstractItemReader

public interface ItemReader<T>

ItemReader defines the batch artifact that reads from a stream of item for chunk processing.

Method Summary

Serializable	checkpointInfo() The checkpointInfo method returns the current checkpoint position for this reader.
void	close() The close method marks the end of use of the item stream.
void	open(Serializable checkpoint) The open method prepare the reader to read items.
T	readItem() The readitem method returns the next item from the stream.

Method Detail

open

void open(Serializable checkpoint)
          throws Exception

The open method prepare the reader to read items. The input parameter represents the last checkpoint for this reader in a given job instance. The checkpoint data is defined by this reader and is provided by the checkpointInfo method. The checkpoint data instructs the reader where to reposition the stream upon job restart. A checkpoint value of null means reposition from the start of stream or rely on an application managed means of determining whether to position for start or restart. The persistent area of the StepContext may be used to implement application managed stream repositioning.

Parameters:

checkpoint - specifies the last checkpoint

Throws:

Exception - is thrown for any errors.

close

void close()
           throws Exception

The close method marks the end of use of the item stream. The reader is free to do any cleanup necessary on the stream.

Throws:

Exception - is thrown for any errors.

readItem

T readItem()
           throws Exception

The readitem method returns the next item from the stream. It returns null to indicate end of stream.

Returns:

next item or null

Throws:

Exception - is thrown for any errors.

checkpointInfo

Serializable checkpointInfo()
                            throws Exception

The checkpointInfo method returns the current checkpoint position for this reader. It is called before a chunk checkpoint is committed.

Returns:

checkpoint data

Throws:

Exception - is thrown for any errors.