Package org.springframework.batch.item.data

Class AbstractPaginatedDataItemReader<T>

java.lang.Object

org.springframework.batch.item.ItemStreamSupport

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

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

org.springframework.batch.item.data.AbstractPaginatedDataItemReader<T>

Type Parameters:

T - Type of item to be read

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>

Direct Known Subclasses:

MongoItemReader, Neo4jItemReader

public abstract class AbstractPaginatedDataItemReader<T>
extends AbstractItemCountingItemStreamItemReader<T>

A base class that handles basic reading logic based on the paginated semantics of Spring Data's paginated facilities. It also handles the semantics required for restartability based on those facilities.

This reader is not thread-safe.

Since:

2.2

Author:

Michael Minella, Glenn Renfro, Mahmoud Ben Hassine

Field Summary

Fields

Modifier and Type	Field	Description
protected int	page
protected int	pageSize
protected Iterator<T>	results

Constructor Summary

Constructors

Constructor	Description
AbstractPaginatedDataItemReader()

Method Summary

Modifier and Type	Method	Description
protected void	doClose()	Close the resources opened in AbstractItemCountingItemStreamItemReader.doOpen().
protected void	doOpen()	Open resources necessary to start reading input.
protected abstract Iterator<T>	doPageRead()	Method this ItemStreamReader delegates to for the actual work of reading a page.
protected T	doRead()	Read next item from input.
protected void	jumpToItem(int itemLastIndex)	Move to the given item index.
void	setPageSize(int pageSize)	The number of items to be read with each page.

Methods inherited from class org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader

close, getCurrentItemCount, isSaveState, open, read, setCurrentItemCount, setMaxItemCount, setSaveState, update

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

Field Details

page

protected volatile int page

pageSize

protected int pageSize

results

protected Iterator<T> results

Constructor Details

AbstractPaginatedDataItemReader

public AbstractPaginatedDataItemReader()

Method Details

setPageSize

public void setPageSize(int pageSize)

The number of items to be read with each page.

Parameters:

pageSize - the number of items. pageSize must be greater than zero.

doRead

@Nullable
protected T doRead()
            throws Exception

Description copied from class: AbstractItemCountingItemStreamItemReader

Read next item from input.

Specified by:

doRead in class AbstractItemCountingItemStreamItemReader<T>

Returns:

an item or null if the data source is exhausted

Throws:

Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

doPageRead

protected abstract Iterator<T> doPageRead()

Method this ItemStreamReader delegates to for the actual work of reading a page. Each time this method is called, the resulting Iterator should contain the items read within the next page.

If the Iterator is empty or null when it is returned, this ItemReader will assume that the input has been exhausted.

Returns:

an Iterator containing the items within a page.

doOpen

protected void doOpen()
               throws Exception

Description copied from class: AbstractItemCountingItemStreamItemReader

Open resources necessary to start reading input.

Specified by:

doOpen in class AbstractItemCountingItemStreamItemReader<T>

Throws:

Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

doClose

protected void doClose()
                throws Exception

Description copied from class: AbstractItemCountingItemStreamItemReader

Close the resources opened in AbstractItemCountingItemStreamItemReader.doOpen().

Specified by:

doClose in class AbstractItemCountingItemStreamItemReader<T>

Throws:

Exception - Allows subclasses to throw checked exceptions for interpretation by the framework

jumpToItem

protected void jumpToItem(int itemLastIndex)
                   throws Exception

Description copied from class: AbstractItemCountingItemStreamItemReader

Move to the given item index. Subclasses should override this method if there is a more efficient way of moving to given index than re-reading the input using AbstractItemCountingItemStreamItemReader.doRead().

Overrides:

jumpToItem in class AbstractItemCountingItemStreamItemReader<T>

Parameters:

itemLastIndex - index of item (0 based) to jump to.

Throws:

Exception - Allows subclasses to throw checked exceptions for interpretation by the framework