Package org.springframework.batch.item.database

Class AbstractPagingItemReader<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.database.AbstractPagingItemReader<T>

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>, org.springframework.beans.factory.InitializingBean

Direct Known Subclasses:

HibernatePagingItemReader, JdbcPagingItemReader, JpaPagingItemReader

public abstract class AbstractPagingItemReader<T>
extends AbstractItemCountingItemStreamItemReader<T>
implements org.springframework.beans.factory.InitializingBean

Abstract ItemStreamReader for to extend when reading database records in a paging fashion.

Implementations should execute queries using paged requests of a size specified in setPageSize(int). Additional pages are requested when needed as AbstractItemCountingItemStreamItemReader.read() method is called, returning an object corresponding to current position.

Since:

2.0

Author:

Thomas Risberg, Dave Syer

Field Summary

Fields

Modifier and Type	Field	Description
protected org.apache.commons.logging.Log	logger
protected List<T>	results

Constructor Summary

Constructors

Constructor	Description
AbstractPagingItemReader()

Method Summary

Modifier and Type	Method	Description
void	afterPropertiesSet()	Check mandatory properties.
protected void	doClose()	Close the resources opened in AbstractItemCountingItemStreamItemReader.doOpen().
protected abstract void	doJumpToPage(int itemIndex)
protected void	doOpen()	Open resources necessary to start reading input.
protected T	doRead()	Read next item from input.
protected abstract void	doReadPage()
int	getPage()	The current page number.
int	getPageSize()	The page size configured for this reader.
protected void	jumpToItem(int itemIndex)	Move to the given item index.
void	setPageSize(int pageSize)	The number of rows to retrieve at a time.

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, setExecutionContextName, setName

Methods inherited from class java.lang.Object

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

Field Details

logger

protected org.apache.commons.logging.Log logger

results

protected volatile List<T> results

Constructor Details

AbstractPagingItemReader

public AbstractPagingItemReader()

Method Details

getPage

public int getPage()

The current page number.

Returns:

the current page

getPageSize

public int getPageSize()

The page size configured for this reader.

Returns:

the page size

setPageSize

public void setPageSize(int pageSize)

The number of rows to retrieve at a time.

Parameters:

pageSize - the number of rows to fetch per page

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Check mandatory properties.

Specified by:

afterPropertiesSet in interface org.springframework.beans.factory.InitializingBean

Throws:

Exception

See Also:

• InitializingBean.afterPropertiesSet()

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

doReadPage

protected abstract void doReadPage()

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 itemIndex)
                   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:

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

Throws:

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

doJumpToPage

protected abstract void doJumpToPage(int itemIndex)