org.springframework.batch.item.database

Class HibernateCursorItemReader<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.HibernateCursorItemReader<T>

All Implemented Interfaces:

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

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

ItemStreamReader for reading database records built on top of Hibernate. It executes the HQL query when initialized iterates over the result set as AbstractItemCountingItemStreamItemReader.read() method is called, returning an object corresponding to current row. The query can be set directly using setQueryString(String), a named query can be used by setQueryName(String), or a query provider strategy can be supplied via setQueryProvider(HibernateQueryProvider).

The reader can be configured to use either StatelessSession sufficient for simple mappings without the need to cascade to associated objects or standard hibernate Session for more advanced mappings or when caching is desired. When stateful session is used it will be cleared in the update(ExecutionContext) method without being flushed (no data modifications are expected).

The implementation is not thread-safe.

Author:

Robert Kasanicky, Dave Syer

Constructor Summary

Constructors

Constructor and Description
HibernateCursorItemReader()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet()
protected void	doClose() Close the cursor and hibernate session.
protected void	doOpen() Open hibernate session and create a forward-only cursor for the query.
protected T	doRead() Read next item from input.
protected void	jumpToItem(int itemIndex) Wind forward through the result set to the item requested.
void	setFetchSize(int fetchSize) Fetch size used internally by Hibernate to limit amount of data fetched from database per round trip.
void	setParameterValues(java.util.Map<java.lang.String,java.lang.Object> parameterValues) The parameter values to apply to a query (map of name:value).
void	setQueryName(java.lang.String queryName) A query name for an externalized query.
void	setQueryProvider(HibernateQueryProvider<T> queryProvider) A query provider.
void	setQueryString(java.lang.String queryString) A query string in HQL.
void	setSessionFactory(org.hibernate.SessionFactory sessionFactory) The Hibernate SessionFactory to use the create a session.
void	setUseStatelessSession(boolean useStatelessSession) Can be set only in uninitialized state.
void	update(ExecutionContext executionContext) Update the context and clear the session if stateful.

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

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

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

Constructor Detail

HibernateCursorItemReader

public HibernateCursorItemReader()

Method Detail

afterPropertiesSet

public void afterPropertiesSet()
                        throws java.lang.Exception

Specified by:

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

Throws:

java.lang.Exception

setParameterValues

public void setParameterValues(java.util.Map<java.lang.String,java.lang.Object> parameterValues)

The parameter values to apply to a query (map of name:value).

Parameters:

parameterValues - the parameter values to set

setQueryName

public void setQueryName(java.lang.String queryName)

A query name for an externalized query. Either this or the { query string or the { query provider should be set.

Parameters:

queryName - name of a hibernate named query

setFetchSize

public void setFetchSize(int fetchSize)

Fetch size used internally by Hibernate to limit amount of data fetched from database per round trip.

Parameters:

fetchSize - the fetch size to pass down to Hibernate

setQueryProvider

public void setQueryProvider(HibernateQueryProvider<T> queryProvider)

A query provider. Either this or the {query string or the {query name should be set.

Parameters:

queryProvider - Hibernate query provider

setQueryString

public void setQueryString(java.lang.String queryString)

A query string in HQL. Either this or the { query provider or the { query name should be set.

Parameters:

queryString - HQL query string

setSessionFactory

public void setSessionFactory(org.hibernate.SessionFactory sessionFactory)

The Hibernate SessionFactory to use the create a session.

Parameters:

sessionFactory - the SessionFactory to set

setUseStatelessSession

public void setUseStatelessSession(boolean useStatelessSession)

Can be set only in uninitialized state.

Parameters:

useStatelessSession - true to use StatelessSession false to use standard hibernate Session

doRead

@Nullable
protected T doRead()
                      throws java.lang.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:

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

doOpen

protected void doOpen()
               throws java.lang.Exception

Open hibernate session and create a forward-only cursor for the query.

Specified by:

doOpen in class AbstractItemCountingItemStreamItemReader<T>

Throws:

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

update

public void update(ExecutionContext executionContext)
            throws ItemStreamException

Update the context and clear the session if stateful.

Specified by:

update in interface ItemStream

Overrides:

update in class AbstractItemCountingItemStreamItemReader<T>

Parameters:

executionContext - the current ExecutionContext

Throws:

ItemStreamException - if there is a problem

See Also:

ItemStream.update(ExecutionContext)

jumpToItem

protected void jumpToItem(int itemIndex)
                   throws java.lang.Exception

Wind forward through the result set to the item requested. Also clears the session every now and then (if stateful) to avoid memory problems. The frequency of session clearing is the larger of the fetch size (if set) and 100.

Overrides:

jumpToItem in class AbstractItemCountingItemStreamItemReader<T>

Parameters:

itemIndex - the first item to read

Throws:

java.lang.Exception - if there is a problem

See Also:

AbstractItemCountingItemStreamItemReader.jumpToItem(int)

doClose

protected void doClose()
                throws java.lang.Exception

Close the cursor and hibernate session.

Specified by:

doClose in class AbstractItemCountingItemStreamItemReader<T>

Throws:

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