org.springframework.batch.item.database.support
Class SingleColumnJdbcKeyCollector

java.lang.Object
  org.springframework.batch.item.ExecutionContextUserSupport
      org.springframework.batch.item.database.support.SingleColumnJdbcKeyCollector

All Implemented Interfaces:

KeyCollector

public class SingleColumnJdbcKeyCollector
extends ExecutionContextUserSupport
implements KeyCollector

Jdbc KeyCollector implementation that only works for a single column key. A sql query must be passed in which will be used to return a list of keys. Each key will be mapped by a RowMapper that returns a mapped key. By default, the SingleColumnRowMapper is used, and will convert keys into well known types at runtime. It is extremely important to note that only one column should be mapped to an object and returned as a key. If multiple columns are returned as a key in this strategy, then restart will not function properly. Instead a strategy that supports keys comprised of multiple columns should be used.

Restartability: Because the key is only one column, restart is made much more simple. Before each commit, the last processed key is returned to be stored as restart data. Upon restart, that same key is given back to restore from, using a separate 'RestartQuery'. This means that only the keys remaining to be processed are returned, rather than returning the original list of keys and iterating forward to that last committed point.

Author:

Lucas Ward

See Also:

SingleColumnRowMapper

Constructor Summary

SingleColumnJdbcKeyCollector()

SingleColumnJdbcKeyCollector(JdbcTemplate jdbcTemplate, String sql)
Constructs a new instance using the provided jdbcTemplate and string representing the sql statement that should be used to retrieve keys.

Method Summary

void	afterPropertiesSet()
List	retrieveKeys(ExecutionContext executionContext) Retrieve the keys to be iterated over.
void	setJdbcTemplate(JdbcTemplate jdbcTemplate) Set the JdbcTemplate to be used.
void	setKeyMapper(RowMapper keyMapper) Set the RowMapper to be used to map each key to an object.
void	setRestartSql(String restartSql) Set the SQL query to be used to return the remaining keys to be processed.
void	setSql(String sql) Set the SQL statement to be used to return the keys to be processed.
void	updateContext(Object key, ExecutionContext executionContext) Get the restart data representing the last processed key.

Methods inherited from class org.springframework.batch.item.ExecutionContextUserSupport

getKey, setName

Methods inherited from class java.lang.Object

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

Constructor Detail

SingleColumnJdbcKeyCollector

public SingleColumnJdbcKeyCollector()

SingleColumnJdbcKeyCollector

public SingleColumnJdbcKeyCollector(JdbcTemplate jdbcTemplate,
                                    String sql)

Constructs a new instance using the provided jdbcTemplate and string representing the sql statement that should be used to retrieve keys.

Parameters:

jdbcTemplate -

sql -

Throws:

IllegalArgumentException - if jdbcTemplate is null.

IllegalArgumentException - if sql string is empty or null.

Method Detail

retrieveKeys

public List retrieveKeys(ExecutionContext executionContext)

Description copied from interface: KeyCollector

Retrieve the keys to be iterated over. If the ExecutionContext provided includes any state relevant to this collector (because it was stored as part of saveState()) then it should start from the point indicated by that state.

In the case of a restart, (i.e. the ExecutionContext contains relevant state) this method should return only the keys that are remaining to be processed. For example, if the are 1,000 keys, and the 500th is processed before the batch job terminates unexpectedly, upon restart keys 501 through 1,000 should be returned.

Specified by:

retrieveKeys in interface KeyCollector

Parameters:

executionContext - ExecutionContext containing any potential initial state that could potentially be used to retrieve the correct keys.

Returns:

list of keys returned by the driving query

updateContext

public void updateContext(Object key,
                          ExecutionContext executionContext)

Get the restart data representing the last processed key.

Specified by:

updateContext in interface KeyCollector

Parameters:

key - to be converted to restart data.

Throws:

IllegalArgumentException - if key is null.

afterPropertiesSet

public void afterPropertiesSet()
                        throws Exception

Throws:

Exception

setKeyMapper

public void setKeyMapper(RowMapper keyMapper)

Set the RowMapper to be used to map each key to an object.

Parameters:

keyMapper -

setRestartSql

public void setRestartSql(String restartSql)

Set the SQL query to be used to return the remaining keys to be processed.

Parameters:

restartSql -

setSql

public void setSql(String sql)

Set the SQL statement to be used to return the keys to be processed.

Parameters:

sql -

setJdbcTemplate

public void setJdbcTemplate(JdbcTemplate jdbcTemplate)

Set the JdbcTemplate to be used.

Parameters:

jdbcTemplate -