[IBATIS-722] Please consider implementing external iterator for results

• Type: New Feature
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Core
• Assignee: Unassigned
• Reporter: Tom Kunicki
• Created: 23/Dec/09 05:31
• Updated: 23/Dec/09 05:31

Description

Please consider implementing an external iterator for mapped results.

iBatis currently offers an internal/push iterator via IoC with SqlSession.select(...) and ResultHandler. This results in complicated client implementations when used with a pull API such as StAX. This requires the introduction of an additional thread, buffering and associated concurrency as well a complication error detection and handling.

The API and associated semantic of an external iterator implementation might look something like this.

String selectId = ...
Object parameters = ...
SqlSessionFactory sqlSessionFactory = ...
SqlSession sqlSession = sqlSessionFactory.openSession();
ResultIterator resultsIterator = sqlSession.selectMultiple(selectID, parameters);
// hand resultIterator off to some pull API (i.e. wrap in StAX XMLEventReader implementation and stream your GiBi of data into the ether, yay!)
...

// the resultIterator API might look like this...
public class ResultIterator implements Iterator<Object> {
// Implement Iterator.next()
public Object next()

{ // return next mapped object // if result set exhausted close it, do cleanup, make sure hasNext() results 'false' ... }

// Implement Iterator.hasNext()
public boolean hasNext()

{ // result set exhausted, stop() called? ... }

// Implement Iterator.remove()
public void remove()

{ // not going to work in this context... throw new UnsupportedOperationException(); }

public stop()

{ // analog to ResultHandler/ResultContext.stop() // do cleanup, i.e. close result set make sure subsequent hasNext() returns 'false' }

}