org.springframework.batch.item.database
Class JdbcPagingItemReader<T>

java.lang.Object
  org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader<T>
      org.springframework.batch.item.database.AbstractPagingItemReader<T>
          org.springframework.batch.item.database.JdbcPagingItemReader<T>

All Implemented Interfaces:

ItemReader<T>, ItemStream, ItemStreamReader<T>, InitializingBean

public class JdbcPagingItemReader<T>
extends AbstractPagingItemReader<T>
implements InitializingBean

ItemReader for reading database records using JDBC in a paging fashion.

It executes the SQL built by the PagingQueryProvider to retrieve requested data. The query is executed using paged requests of a size specified in AbstractPagingItemReader.setPageSize(int). Additional pages are requested when needed as AbstractItemCountingItemStreamItemReader.read() method is called, returning an object corresponding to current position. On restart it uses the last sort key value to locate the first page to read (so it doesn't matter if the successfully processed itmes have been removed or modified).

The performance of the paging depends on the database specific features available to limit the number of returned rows. Setting a fairly large page size and using a commit interval that matches the page size should provide better performance.

The implementation is thread-safe in between calls to open(ExecutionContext), but remember to use saveState=false if used in a multi-threaded client (no restart available).

Since:

2.0

Author:

Thomas Risberg, Dave Syer

Field Summary

static int

VALUE_NOT_SET

Fields inherited from class org.springframework.batch.item.database.AbstractPagingItemReader

logger, results

Constructor Summary

JdbcPagingItemReader()

Method Summary

void	afterPropertiesSet() Check mandatory properties.
protected void	doJumpToPage(int itemIndex)
protected void	doReadPage()
void	open(ExecutionContext executionContext) Open the stream for the provided ExecutionContext.
void	setDataSource(DataSource dataSource)
void	setFetchSize(int fetchSize) Gives the JDBC driver a hint as to the number of rows that should be fetched from the database when more rows are needed for this ResultSet object.
void	setParameterValues(Map<String,Object> parameterValues) The parameter values to be used for the query execution.
void	setQueryProvider(PagingQueryProvider queryProvider) A PagingQueryProvider.
void	setRowMapper(RowMapper rowMapper) The row mapper implementation to be used by this reader.
void	update(ExecutionContext executionContext) Indicates that the execution context provided during open is about to be saved.

Methods inherited from class org.springframework.batch.item.database.AbstractPagingItemReader

doClose, doOpen, doRead, getPage, getPageSize, jumpToItem, setPageSize

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

close, getCurrentItemCount, getExecutionContextUserSupport, isSaveState, read, setCurrentItemCount, setMaxItemCount, setName, setSaveState

Methods inherited from class java.lang.Object

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

Field Detail

VALUE_NOT_SET

public static final int VALUE_NOT_SET

See Also:

Constant Field Values

Constructor Detail

JdbcPagingItemReader

public JdbcPagingItemReader()

Method Detail

setDataSource

public void setDataSource(DataSource dataSource)

setFetchSize

public void setFetchSize(int fetchSize)

Gives the JDBC driver a hint as to the number of rows that should be fetched from the database when more rows are needed for this ResultSet object. If the fetch size specified is zero, the JDBC driver ignores the value.

Parameters:

fetchSize - the number of rows to fetch

See Also:

ResultSet.setFetchSize(int)

setQueryProvider

public void setQueryProvider(PagingQueryProvider queryProvider)

A PagingQueryProvider. Supplies all the platform dependent query generation capabilities needed by the reader.

Parameters:

queryProvider - the PagingQueryProvider to use

setRowMapper

public void setRowMapper(RowMapper rowMapper)

The row mapper implementation to be used by this reader. The row mapper is used to convert result set rows into objects, which are then returned by the reader.

Parameters:

rowMapper - a ParameterizedRowMapper implementation

setParameterValues

public void setParameterValues(Map<String,Object> parameterValues)

The parameter values to be used for the query execution. If you use named parameters then the key should be the name used in the query clause. If you use "?" placeholders then the key should be the relative index that the parameter appears in the query string built using the select, from and where clauses specified.

Parameters:

parameterValues - the values keyed by the parameter named/index used in the query string.

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Check mandatory properties.

Specified by:

afterPropertiesSet in interface InitializingBean

Overrides:

afterPropertiesSet in class AbstractPagingItemReader<T>

Throws:

Exception

See Also:

InitializingBean.afterPropertiesSet()

doReadPage

protected void doReadPage()

Specified by:

doReadPage in class AbstractPagingItemReader<T>

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

Overrides:

update in class AbstractItemCountingItemStreamItemReader<T>

Parameters:

executionContext - to be updated

Throws:

ItemStreamException

open

public void open(ExecutionContext executionContext)

Description copied from interface: ItemStream

Open the stream for the provided ExecutionContext.

Specified by:

open in interface ItemStream

Overrides:

open in class AbstractItemCountingItemStreamItemReader<T>

doJumpToPage

protected void doJumpToPage(int itemIndex)

Specified by:

doJumpToPage in class AbstractPagingItemReader<T>