javax.batch.api.chunk

Interface ItemReader

All Known Implementing Classes:

AbstractItemReader

public interface ItemReader

ItemReader defines the batch artifact that reads items for chunk processing.

Method Summary

Modifier and Type	Method and Description
Serializable	checkpointInfo() The checkpointInfo method returns the current checkpoint data for this reader.
void	close() The close method marks the end of use of the ItemReader.
void	open(Serializable checkpoint) The open method prepares the reader to read items.
Object	readItem() The readItem method returns the next item for chunk processing.

Method Detail

open

void open(Serializable checkpoint)
   throws Exception

The open method prepares 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 provides the reader whatever information it needs to resume reading items upon restart. A checkpoint value of null is passed upon initial start.

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 ItemReader. The reader is free to do any cleanup necessary.

Throws:

Exception - is thrown for any errors.

readItem

Object readItem()
         throws Exception

The readItem method returns the next item for chunk processing. It returns null to indicate no more items, which also means the current chunk will be committed and the step will end.

Returns:

next item or null

Throws:

Exception - is thrown for any errors.

checkpointInfo

Serializable checkpointInfo()
                     throws Exception

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

Returns:

checkpoint data

Throws:

Exception - is thrown for any errors.