org.springframework.batch.item.data

Class MongoItemReader<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>

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

All Implemented Interfaces:

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

public class MongoItemReader<T>
extends AbstractPaginatedDataItemReader<T>
implements org.springframework.beans.factory.InitializingBean

Restartable ItemReader that reads documents from MongoDB via a paging technique.

It executes the JSON setQuery(String) to retrieve the requested documents. The query is executed using paged requests specified in the AbstractPaginatedDataItemReader.setPageSize(int). Additional pages are requested as needed to provide data when the AbstractItemCountingItemStreamItemReader.read() method is called.

The JSON query provided supports parameter substitution via ?<index> placeholders where the <index> indicates the index of the parameterValue to substitute.

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

Author:

Michael Minella

Field Summary

Fields inherited from class org.springframework.batch.item.data.AbstractPaginatedDataItemReader

page, pageSize, results

Constructor Summary

Constructors

Constructor and Description
MongoItemReader()

Method Summary

Methods

Modifier and Type	Method and Description
void	afterPropertiesSet() Checks mandatory properties
protected Iterator<T>	doPageRead() Method this ItemStreamReader delegates to for the actual work of reading a page.
void	setCollection(String collection)
void	setFields(String fields) JSON defining the fields to be returned from the matching documents by MongoDB.
void	setHint(String hint) JSON String telling MongoDB what index to use.
void	setParameterValues(List<Object> parameterValues) List of values to be substituted in for each of the parameters in the query.
void	setQuery(String query) A JSON formatted MongoDB query.
void	setSort(Map<String,org.springframework.data.domain.Sort.Direction> sorts) Map of property names/Sort.Direction values to sort the input by.
void	setTargetType(Class<? extends T> type) The type of object to be returned for each AbstractItemCountingItemStreamItemReader.read() call.
void	setTemplate(org.springframework.data.mongodb.core.MongoOperations template) Used to perform operations against the MongoDB instance.

Methods inherited from class org.springframework.batch.item.data.AbstractPaginatedDataItemReader

doClose, doOpen, doRead, jumpToItem, setPageSize

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

Constructor Detail

MongoItemReader

public MongoItemReader()

Method Detail

setTemplate

public void setTemplate(org.springframework.data.mongodb.core.MongoOperations template)

Used to perform operations against the MongoDB instance. Also handles the mapping of documents to objects.

Parameters:

template - the MongoOperations instance to use

See Also:

MongoOperations

setQuery

public void setQuery(String query)

A JSON formatted MongoDB query. Parameterization of the provided query is allowed via ?<index> placeholders where the <index> indicates the index of the parameterValue to substitute.

Parameters:

query - JSON formatted Mongo query

setTargetType

public void setTargetType(Class<? extends T> type)

The type of object to be returned for each AbstractItemCountingItemStreamItemReader.read() call.

Parameters:

type - the type of object to return

setParameterValues

public void setParameterValues(List<Object> parameterValues)

List of values to be substituted in for each of the parameters in the query.

Parameters:

parameterValues -

setFields

public void setFields(String fields)

JSON defining the fields to be returned from the matching documents by MongoDB.

Parameters:

fields - JSON string that identifies the fields to sorty by.

setSort

public void setSort(Map<String,org.springframework.data.domain.Sort.Direction> sorts)

Map of property names/Sort.Direction values to sort the input by.

Parameters:

sorts - map of properties and direction to sort each.

setCollection

public void setCollection(String collection)

Parameters:

collection - Mongo collection to be queried.

setHint

public void setHint(String hint)

JSON String telling MongoDB what index to use.

Parameters:

hint - string indicating what index to use.

doPageRead

protected Iterator<T> doPageRead()

Description copied from class: AbstractPaginatedDataItemReader

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.

Specified by:

doPageRead in class AbstractPaginatedDataItemReader<T>

Returns:

an Iterator containing the items within a page.

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Checks mandatory properties

Specified by:

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

Throws:

Exception

See Also:

InitializingBean.afterPropertiesSet()